diff --git a/Java/ShortURL.java b/Java/ShortURL.java
index 66d340a..f83cea6 100644
--- a/Java/ShortURL.java
+++ b/Java/ShortURL.java
@@ -14,6 +14,9 @@
  *
  * Source: https://github.com/delight-im/ShortURL (Apache License 2.0)
  */
+
+import java.math.BigInteger;
+
 public class ShortURL {
 
     public static final String ALPHABET = "23456789bcdfghjkmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ-_";
@@ -31,9 +34,42 @@ public static String encode(int num) {
     public static int decode(String str) {
         int num = 0;
         for (int i = 0; i < str.length(); i++) {
+            char c = str.charAt(i);
+            if (ALPHABET.indexOf(c) < 0) {
+                num = -1;
+                break;
+            }
             num = num * BASE + ALPHABET.indexOf(str.charAt(i));
         }
         return num;
     }
 
+    public static String encode(String num) throws NumberFormatException {
+        BigInteger bnum = new BigInteger(num);
+        BigInteger bBase = new BigInteger(Integer.toString(BASE));
+        StringBuilder str = new StringBuilder();
+        while (bnum.compareTo(BigInteger.ZERO) > 0) {
+            int n = bnum.mod(bBase).intValue();
+            str.insert(0, ALPHABET.charAt(n));
+            bnum = bnum.divide(bBase);
+        }
+
+        return str.toString();
+    }
+
+    public static BigInteger decodeWithBigNumber(String str) {
+        BigInteger bNum = new BigInteger("0");
+        BigInteger bBase = new BigInteger(Integer.toString(BASE));
+        for (int i = 0; i < str.length(); i++) {
+            char c = str.charAt(i);
+            if (ALPHABET.indexOf(c) < 0) {
+                bNum = new BigInteger("-1");
+                break;
+            }
+            BigInteger br = new BigInteger(Integer.toString(ALPHABET.indexOf(c)));
+            bNum = bNum.multiply(bBase).add(br);
+        }
+
+        return bNum;
+    }
 }
diff --git a/JavaScript/ShortURL.js b/JavaScript/ShortURL.js
index 5e05282..1c2ead1 100644
--- a/JavaScript/ShortURL.js
+++ b/JavaScript/ShortURL.js
@@ -14,6 +14,9 @@
  *
  * Source: https://github.com/delight-im/ShortURL (Apache License 2.0)
  */
+
+var bigInt = require("big-integer");
+
 var ShortURL = new function() {
 
     var _alphabet = '23456789bcdfghjkmnpqrstvwxyzBCDFGHJKLMNPQRSTVWXYZ-_',
@@ -28,6 +31,20 @@ var ShortURL = new function() {
         return str;
     };
 
+    /**
+     * @param {num} input number represented by string
+     * @return {str} encoded short url
+     */
+    this.encodeBigInteger = function (num) {
+        var str = '';
+        var bNum = bigInt(num);
+        while (bNum.compare(0) == 1) {
+            str = _alphabet.charAt(bNum.mod(_base)) + str;
+            bNum = bNum.divide(_base);
+        }
+        return str;
+    }
+
     this.decode = function(str) {
         var num = 0;
         for (var i = 0; i < str.length; i++) {
@@ -36,4 +53,17 @@ var ShortURL = new function() {
         return num;
     };
 
+
+    /**
+     * @param {str} ShortURL represented by string
+     * @return {str} decoded number represented by string
+     */
+    this.decodeBigInteger = function(str) {
+        var bNum = bigInt(0);
+        for (var i = 0; i < str.length; i++) {
+            bNum = bNum.multiply(_base).add(_alphabet.indexOf(str.charAt(i)));
+        }
+        return bNum;
+    }
+
 };