StringBuffer Replace method Example

class StringBufferReplace{ 
  public static void main(String[] args) {
 
     //Create StringBuffer object
     StringBuffer sb = new StringBuffer("This is a String");
     System.out.println("Before: " + sb);
 
     /* public StringBuffer replace(int start, int end, String str):
      * It replaces the part of the content (substring starting from
      * index start and ending with index end-1) of StringBuffer with 
      * the specified string "str" 
      */
     sb.replace(10,16,"TEXT");
     System.out.println("After: " + sb);
  }
}

Output:

Before: This is a String
After: This is a TEXT

More about replace() method from javadoc:
public StringBuffer replace(int start, int end, String str): Replaces the substring of original string with the specified String. The substring begins at the specified index start and ends at index end – 1. First the characters in the substring are removed and then the specified String is inserted at start. (This sequence will be lengthened to accommodate the specified String if necessary.)

Parameters:
start – The beginning index, inclusive.
end – The ending index, exclusive.
str – String that will replace previous contents.

It throws:
StringIndexOutOfBoundsException – if start index is negative, greater than length(), or greater than specified index end.