Added method stringByReplacingOccurrencesOfStringWithString and testcase for the same.

Foundation/CPString.j

@@ -232,6 +232,7 @@ var CPStringHashes      = new objj_dictionary();
     if (difference) string += substring.substr(difference + substring.length);
 }
 
+//Dividing Strings
 /*
     Tokenizes the receiver string using the specified
     delimiter. For example, if the receiver is:
@@ -351,6 +352,36 @@ var CPStringHashes      = new objj_dictionary();
     return CPMakeRange(location, location == CPNotFound ? 0 : aString.length);
 }
 
+//Replacing Substrings
+
+/*
+    Returns a new string in which all occurrences of a target string in the reciever are replaced by 
+    another given string.
+    @param target The string to replace.
+    @param replacement the string with which to replace the <pre>target<pre>
+*/
+
+- (CPString)stringByReplacingOccurrencesOfString:(CPString)target withString:(CPString)replacement
+{
+    return self.replace(new RegExp(target, "g"), replacement);
+}
+/*
+- (CPString)stringByReplacingOccurrencesOfString:(CPString)target 
+                                      withString:(CPString)replacement 
+                                         options:(int)options 
+                                           range:(CPRange)searchRange
+{
+    //TODO :Vijay implement the method
+
+}
+
+- (CPString)stringByReplacingCharactersInRange:(CPRange)range withString:(CPString)replacement
+{
+    //TODO :Vijay implement the method
+}
+*/
+
+
 // Identifying and comparing strings
 /*
     Compares the receiver to the specified string.

Tests/Foundation/CPStringTest.j

@@ -2,6 +2,18 @@ import <Foundation/CPString.j>
 
 @implementation CPStringTest : OJTestCase
 
+
+- (void)testStringByReplacingOccurrencesOfStringWithString
+{
+    var expectedString = @"hello world. A new world!";
+    var dummyString = @"hello woold. A new woold!";
+    var actualString = [dummyString stringByReplacingOccurrencesOfString:@"woold" withString:@"world"];
+    [self assertTrue:(expectedString === actualString) 
+             message:"stringByAppendingFormat: expected:" + expectedString + " actual:" + actualString];
+    
+    
+    
+}
 - (void)testStringByAppendingFormat
 {
     var format = @"%d X %d = %d";