diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/Accessible/isPackagePrivate/accipp001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/Accessible/isPackagePrivate/accipp001.java
index 7378c4dc96b..201995bde3f 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/Accessible/isPackagePrivate/accipp001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/Accessible/isPackagePrivate/accipp001.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -108,8 +108,7 @@ private int runThis (String argv[], PrintStream out) {
         logHandler      = new Log(out, argsHandler);
         Binder binder   = new Binder(argsHandler, logHandler);
 
-        debugee = Debugee.prepareDebugee(argsHandler, logHandler,
-                debugeeName + (argsHandler.verbose() ? " -vbs" : ""));
+        debugee = Debugee.prepareDebugee(argsHandler, logHandler, debugeeName);
 
 //        ReferenceType classes[] = debugee.classes();
 //        for (int i=0; i<classes.length; i++) {
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequest/hashCode/hashcode001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequest/hashCode/hashcode001.java
index 05756d91327..1affebe18a6 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequest/hashCode/hashcode001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequest/hashCode/hashcode001.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -118,7 +118,7 @@ private static void execTest() {
             switch (i) {
 
                 case 0:
-                       ThreadReference thread = debuggee.threadByNameOrThrow(methodName);
+                       ThreadReference thread = debuggee.mainThread();
 
                        display(".....setting up StepRequest");
                        eventRequest = eventRequestManager.createStepRequest
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequestManager/_bounds_/requests001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequestManager/_bounds_/requests001.java
index 36ade0bcc70..8fb2c012b7b 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequestManager/_bounds_/requests001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventRequestManager/_bounds_/requests001.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -95,7 +95,7 @@ private void execTest() {
 
         EventRequest request;
         EventRequestManager evm = debugee.getEventRequestManager();
-        ThreadReference thread = debugee.threadByName("main");
+        ThreadReference thread = debugee.mainThread();
 
         display("");
         display("...calling createStepRequest(null, StepRequest.STEP_LINE, "
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventSet/suspendPolicy/suspendpolicy001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventSet/suspendPolicy/suspendpolicy001.java
index d145bf46136..17e515af080 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventSet/suspendPolicy/suspendpolicy001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/EventSet/suspendPolicy/suspendpolicy001.java
@@ -250,6 +250,7 @@ private void testRun()
 
         ClassPrepareEvent event = (ClassPrepareEvent) eventIterator.next();
         debuggeeClass = event.referenceType();
+        debuggee.setMainThread(event.thread());
 
         if (!debuggeeClass.name().equals(debuggeeName))
            throw new JDITestRuntimeException("** Unexpected ClassName for ClassPrepareEvent **");
@@ -257,7 +258,7 @@ private void testRun()
 
         log2("......setting up ClassPrepareEvent for breakpointForCommunication");
 
-        ThreadReference mainThread = debuggee.threadByNameOrThrow("main");
+        ThreadReference mainThread = debuggee.mainThread();
         setupBreakpointForCommunication(debuggeeClass);
 
     //------------------------------------------------------  testing section
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/Method/isObsolete/isobsolete003.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/Method/isObsolete/isobsolete003.java
index 0f6339b0ae4..f9084ef3d94 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/Method/isObsolete/isobsolete003.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/Method/isObsolete/isobsolete003.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -139,7 +139,7 @@ public static int run(String argv[], PrintStream out) {
 
     private static void execTest() {
 
-        ThreadReference mainThread = debuggee.threadByName("main");
+        ThreadReference mainThread = debuggee.mainThread();
 
         // Set first breakpoint to have isobsolete003b class loaded.
         BreakpointRequest bpRequest = debuggee.makeBreakpoint(debuggeeClass, "main", brkpMainLineNumber);
@@ -456,6 +456,7 @@ private static void waitForDebuggeeClassPrepared () {
         ClassPrepareEvent event = (ClassPrepareEvent) waitForEvent(cpRequest);
         cpRequest.disable();
 
+        debuggee.setMainThread(event.thread());
         debuggeeClass = event.referenceType();
         if (!debuggeeClass.name().equals(debuggeeName))
            throw new Failure("Unexpected class name for ClassPrepareEvent : " + debuggeeClass.name());
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodEntryEvent/method/method002.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodEntryEvent/method/method002.java
index 20a1cfb6cdf..e230a8dc072 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodEntryEvent/method/method002.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodEntryEvent/method/method002.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -113,6 +113,9 @@ public static int run(final String args[], final PrintStream out) {
 
         pipe = debuggee.createIOPipe();
 
+        ClassPrepareEvent cpEvent = debuggee.waitForClassPrepare(DEBUGGEE_NAME);
+        debuggee.setMainThread(cpEvent.thread());
+
         // resume debuggee
         log.display("Resuming debuggee");
         debuggee.resume();
@@ -135,7 +138,7 @@ public static int run(final String args[], final PrintStream out) {
             checkedClass = debuggee.classByName(CHILD_NAME);
 
             log.display("Getting <main> thread in debuggee");
-            checkedThread = debuggee.threadByName("main");
+            checkedThread = debuggee.mainThread();
             if (checkedThread == null) {
                 throw new Failure("TEST BUG: unable to find reference to main thread");
             }
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method001.java
index a1515979a18..98e9b31c965 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method001.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -110,6 +110,9 @@ public static int run(final String args[], final PrintStream out) {
 
         pipe = debuggee.createIOPipe();
 
+        ClassPrepareEvent cpEvent = debuggee.waitForClassPrepare(DEBUGGEE_NAME);
+        debuggee.setMainThread(cpEvent.thread());
+
         // resume debuggee
         log.display("Resuming debuggee");
         debuggee.resume();
@@ -131,7 +134,7 @@ public static int run(final String args[], final PrintStream out) {
             checkedClass = debuggee.classByName(DEBUGGEE_NAME);
 
             log.display("Getting reference to thread <main>");
-            checkedThread = debuggee.threadByName("main");
+            checkedThread = debuggee.mainThread();
             if (checkedThread == null) {
                 throw new Failure("TEST BUG: unable to find reference to main thread");
             }
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method002.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method002.java
index 0f0bd3773f3..b7c6eb705b1 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method002.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/MethodExitEvent/method/method002.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -114,6 +114,9 @@ public static int run(final String args[], final PrintStream out) {
 
         pipe = debuggee.createIOPipe();
 
+        ClassPrepareEvent cpEvent = debuggee.waitForClassPrepare(DEBUGGEE_NAME);
+        debuggee.setMainThread(cpEvent.thread());
+
         // resume debuggee
         log.display("Resuming debuggee");
         debuggee.resume();
@@ -136,7 +139,7 @@ public static int run(final String args[], final PrintStream out) {
             checkedClass = debuggee.classByName(CHILD_NAME);
 
             log.display("Getting reference to thread <main>");
-            checkedThread = debuggee.threadByName("main");
+            checkedThread = debuggee.mainThread();
             if (checkedThread == null) {
                 throw new Failure("TEST BUG: unable to find reference to main thread");
             }
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/entryCount/entrycount002.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/entryCount/entrycount002.java
index 7736eae1d2b..aef3dfde0da 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/entryCount/entrycount002.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/entryCount/entrycount002.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -153,7 +153,7 @@ private int runThis(String argv[], PrintStream out) {
     //--------------------------------------------------------- mutable common methods
 
     private void execTest() {
-        ThreadReference mainThread = debuggee.threadByName("main");
+        ThreadReference mainThread = debuggee.mainThread();
 
         BreakpointRequest bpRequest = debuggee.makeBreakpoint(debuggeeClass,
                                                             "methodForCommunication",
@@ -290,6 +290,8 @@ private ReferenceType waitForDebuggeeClassPrepared () {
         ClassPrepareEvent event = (ClassPrepareEvent) waitForEvent(cpRequest);
         cpRequest.disable();
 
+        debuggee.setMainThread(event.thread()); // Needed so debuggee.mainThread() will work
+
         if (!event.referenceType().name().equals(debuggeeName)) {
            throw new Failure("Unexpected class name for ClassPrepareEvent : " + debuggeeClass.name());
         }
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/owningThread/owningthread002.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/owningThread/owningthread002.java
index 89d1b703310..af940a69270 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/owningThread/owningthread002.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/ObjectReference/owningThread/owningthread002.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -153,7 +153,7 @@ private int runThis(String argv[], PrintStream out) {
     //--------------------------------------------------------- mutable common methods
 
     private void execTest() {
-        ThreadReference mainThread = debuggee.threadByName("main");
+        ThreadReference mainThread = debuggee.mainThread();
 
         BreakpointRequest bpRequest = debuggee.makeBreakpoint(debuggeeClass,
                                                              "methodForCommunication",
@@ -298,6 +298,8 @@ private ReferenceType waitForDebuggeeClassPrepared () {
         ClassPrepareEvent event = (ClassPrepareEvent) waitForEvent(cpRequest);
         cpRequest.disable();
 
+        debuggee.setMainThread(event.thread()); // Needed so debuggee.mainThread() will work
+
         if (!event.referenceType().name().equals(debuggeeName)) {
            throw new Failure("Unexpected class name for ClassPrepareEvent : " + debuggeeClass.name());
         }
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/StackFrame/_bounds_/bounds002.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/StackFrame/_bounds_/bounds002.java
index 092e0beb983..7a9f5f0547e 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/StackFrame/_bounds_/bounds002.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/StackFrame/_bounds_/bounds002.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -95,7 +95,7 @@ public static int run(String argv[], PrintStream out) {
     private void execTest() {
 
         debugee.VM().suspend();
-        ThreadReference thread = debugee.threadByName("main");
+        ThreadReference thread = debugee.mainThread();
         StackFrame stackFrame = null;
         boolean isTopmostFrame = false;
         try {
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/StepRequest/_bounds_/filters001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/StepRequest/_bounds_/filters001.java
index 7ec7b0bb5a0..a415d5dd6ff 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/StepRequest/_bounds_/filters001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/StepRequest/_bounds_/filters001.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -87,7 +87,7 @@ private void execTest() {
         display("");
         display(">>>creating StepRequest");
 
-        ThreadReference thread = debugee.threadByName("main");
+        ThreadReference thread = debugee.mainThread();
         EventRequestManager evm = debugee.getEventRequestManager();
         StepRequest request = evm.createStepRequest(thread, StepRequest.STEP_LINE,
                                                             StepRequest.STEP_INTO);
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/ThreadReference/_bounds_/bounds001.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/ThreadReference/_bounds_/bounds001.java
index 13355b1b125..9e6b52d8be4 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/ThreadReference/_bounds_/bounds001.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/ThreadReference/_bounds_/bounds001.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -97,7 +97,7 @@ public static int run(String argv[], PrintStream out) {
     private void execTest() {
 
         debugee.VM().suspend();
-        ThreadReference thread = debugee.threadByName("main");
+        ThreadReference thread = debugee.mainThread();
 
         display("\nTEST BEGINS");
         display("===========");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses004.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses004.java
index cbccac467e7..f05b7dd1ed7 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses004.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses004.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -158,7 +158,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             display("\n\n<<<Debugee is suspended>>>");
             display("--------------------------");
@@ -167,7 +167,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             display("\n\n<<<Debugee is not suspended>>>");
             display("------------------------------");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses005.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses005.java
index 92e1a4617c8..78a888e6d4d 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses005.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses005.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -155,7 +155,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -165,7 +165,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses006.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses006.java
index c12295948a0..fab18f6b374 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses006.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses006.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -157,7 +157,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -167,7 +167,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses007.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses007.java
index cafe5e05c35..a6340f30d4c 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses007.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses007.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -164,7 +164,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -174,7 +174,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses008.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses008.java
index 5ebc7d5442f..2fcc2ba2188 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses008.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses008.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -162,7 +162,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -172,7 +172,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses009.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses009.java
index 38e0093570c..91e7d1b0caa 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses009.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses009.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -154,7 +154,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -164,7 +164,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses010.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses010.java
index 8d6fc4ac3c4..98465a87836 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses010.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses010.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -156,7 +156,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -166,7 +166,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses011.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses011.java
index 573c60f5cb3..ed08a793ebd 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses011.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses011.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -158,7 +158,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -168,7 +168,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses012.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses012.java
index 23aac498c87..8b1d0bf6e0a 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses012.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses012.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -154,7 +154,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -164,7 +164,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses013.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses013.java
index e0b344e51a0..0bee7b62655 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses013.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses013.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -161,7 +161,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -171,7 +171,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses014.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses014.java
index b664992fcc3..a2147234d2a 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses014.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses014.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -162,7 +162,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -172,7 +172,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses015.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses015.java
index 083ceabc71d..288fb024f98 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses015.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses015.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -182,7 +182,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -192,7 +192,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses016.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses016.java
index 10ab031738b..812bf0d96a9 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses016.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses016.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -163,7 +163,7 @@ private void execTest() throws TestBug {
         display("\nTEST BEGINS");
         display("===========");
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
@@ -173,7 +173,6 @@ private void execTest() throws TestBug {
 
         debugee.resume();
 
-        thrd = debugee.threadByName("main");
         if (!thrd.isSuspended()) {
             statDebugee = "Debugee is not suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses020.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses020.java
index 2d722a65bce..32182359084 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses020.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses020.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -236,7 +236,7 @@ private Map<? extends com.sun.jdi.ReferenceType,byte[]> mapClassToBytes(String f
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses021.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses021.java
index 540573bf071..2b64ce73325 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses021.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses021.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -233,7 +233,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses022.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses022.java
index f703383d024..a818c152c36 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses022.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses022.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -234,7 +234,7 @@ private Map<? extends com.sun.jdi.ReferenceType,byte[]> mapClassToBytes(String f
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses024.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses024.java
index 2c9c861908e..909f254ffac 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses024.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses024.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -292,7 +292,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses025.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses025.java
index dc3d8ff896f..fa9748ddd10 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses025.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses025.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -267,7 +267,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses026.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses026.java
index 9b391ac4459..e9c48d0d6c5 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses026.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses026.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -206,7 +206,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses027.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses027.java
index 6dc6ef4704f..ae29c6f9ef8 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses027.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses027.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -265,7 +265,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses028.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses028.java
index b22368d6b39..818b5f382f8 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses028.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses028.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -210,7 +210,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses030.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses030.java
index 3c7a028b5a8..5e9b921258e 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses030.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses030.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -231,7 +231,7 @@ private String typePrompt(ReferenceType refType) {
     }
 
     void displayVMStatus() {
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
         if (thrd.isSuspended()) {
             statDebugee = "Debugee is suspended";
             display("\n\n<<<" + statDebugee + ">>>");
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses031.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses031.java
index d0f65a08d70..11ee58817d1 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses031.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses031.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -140,7 +140,7 @@ private void execTest() throws Failure {
 
         display("Tested class\t:" + debugeeClass.name());
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
 
         StepRequest sreq;
         BreakpointRequest brkp;
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses032.java b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses032.java
index d36ce86835f..2b50e81ab26 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses032.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/jdi/VirtualMachine/redefineClasses/redefineclasses032.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -124,7 +124,7 @@ private void execTest() throws Failure {
 
         display("Tested class\t:" + debugeeClass.name());
 
-        ThreadReference thrd = debugee.threadByName("main");
+        ThreadReference thrd = debugee.mainThread();
 
         BreakpointRequest brkp = debugee.setBreakpoint(debugeeClass,
                                             redefineclasses032a.brkpMethodName,
diff --git a/test/hotspot/jtreg/vmTestbase/nsk/share/jdi/Debugee.java b/test/hotspot/jtreg/vmTestbase/nsk/share/jdi/Debugee.java
index 0f0b6fe9052..b121bd15fe3 100644
--- a/test/hotspot/jtreg/vmTestbase/nsk/share/jdi/Debugee.java
+++ b/test/hotspot/jtreg/vmTestbase/nsk/share/jdi/Debugee.java
@@ -38,11 +38,11 @@
  * This class is wrapper for debugee VM constructed by <code>Binder</code>
  * and it uses <code>com.sun.jdi.VirtualMachine</code> to interact with debugee VM.
  * <p>
- * In addition to the general abities to control of debugee VM process,
+ * In addition to the general abilities to control the debugee VM process
  * provided by the base class <code>DebugeeProcess</code>, this class
  * adds also several service methods over the JDI features to simplify interaction
  * with debugee VM (such as finding classes, setting breakpoints,
- * handling events, and so on.).
+ * handling events, and so on).
  *
  * @see Binder
  * @see DebugeeProcess
@@ -61,11 +61,18 @@ public class Debugee extends DebugeeProcess {
     /** Argument handler. */
     protected ArgumentHandler argumentHandler = null;
 
+    /** wait time in ms. */
+    protected long waitTime;
+
+    /** Stashed ThreadReference for debuggee "main" thread. Not always setup. */
+    protected ThreadReference mainThread;
+
     /** Create new <code>Debugee</code> object for a given binder. */
     protected Debugee (Binder binder) {
         super(binder);
         this.binder = binder;
         this.argumentHandler = (ArgumentHandler)binder.getArgumentHandler();
+        this.waitTime = argumentHandler.getWaitTime() * 60000;
     }
 
     protected Debugee (Process process, Binder binder) {
@@ -73,6 +80,7 @@ protected Debugee (Process process, Binder binder) {
         this.process = process;
         this.binder = binder;
         this.argumentHandler = (ArgumentHandler)binder.getArgumentHandler();
+        this.waitTime = argumentHandler.getWaitTime() * 60000;
     }
 
     /** Setup <code>Debugee</code> object with given VM mirror. */
@@ -264,6 +272,21 @@ public ThreadReference threadByNameOrThrow(String name) throws JDITestRuntimeExc
         throw new JDITestRuntimeException("** Thread IS NOT found ** : " + name);
     }
 
+    public void setMainThread(ThreadReference thread) {
+        String threadName = thread.name();
+        if (!threadName.equals("main")) {
+            throw new TestBug("Thread is not \"main\" thread: " + threadName);
+        }
+        mainThread = thread;
+    }
+
+    public ThreadReference mainThread() {
+        if (mainThread == null) {
+            throw new JDITestRuntimeException("** mainThrad has not been set **");
+        }
+        return mainThread;
+    }
+
     /**
      * Return a debuggee thread by fetching it from a static field in the debuggee.
      */
@@ -576,8 +599,13 @@ public static Debugee prepareDebugee(ArgumentHandler argHandler, Log log,
         Debugee debugee = binder.bindToDebugee(mainClassName);
 
         debugee.createIOPipe();
-
         debugee.redirectStderr(log, DEBUGEE_STDERR_LOG_PREFIX);
+
+        // Get the ClassPrepareEvent for the main class for the sole purpose
+        // of using it to get the ThreadReference for the "main" thread.
+        ClassPrepareEvent cpEvent = debugee.waitForClassPrepare(mainClassName);
+        debugee.setMainThread(cpEvent.thread());
+
         debugee.resume();
 
         debugee.receiveExpectedSignal("ready");
@@ -585,6 +613,37 @@ public static Debugee prepareDebugee(ArgumentHandler argHandler, Log log,
         return debugee;
     }
 
+    public ClassPrepareEvent waitForClassPrepare(String classname) {
+        Event event;
+        EventRequestManager eventRManager = getEventRequestManager();
+        ClassPrepareRequest cpRequest = eventRManager.createClassPrepareRequest();
+        cpRequest.setSuspendPolicy(EventRequest.SUSPEND_ALL);
+        cpRequest.addClassFilter(classname);
+        cpRequest.addCountFilter(1);
+
+        cpRequest.enable();
+        vm.resume();
+        try {
+            event = (ClassPrepareEvent)waitingEvent(cpRequest, waitTime);
+        } catch (InterruptedException e) {
+            throw new Failure("Thread interrupted while waiting for ClassPrepareEvent: " + e);
+        }
+        cpRequest.disable();
+
+        if (!(event instanceof ClassPrepareEvent)) {
+            throw new Failure("Unexpected Event: " + event);
+        }
+
+        ClassPrepareEvent cpEvent = (ClassPrepareEvent)event;
+        ReferenceType cls = cpEvent.referenceType();
+        if (!cls.name().equals(classname)) {
+            throw new Failure("Unexpected ClassName for ClassPrepareEvent: " + cls.name());
+        }
+
+        display("received: ClassPrepareEvent for class: " + classname);
+        return cpEvent;
+    }
+
     /**
      * Send <code>"quit"</code> signal, wait for debugee VM exit and check exit.
      *