public class Demo { public static void main(String[] args) { String str = "The Walking Dead!"; System.out.println("String: "+str); String subStr1 = "Dead"; String subStr2 = "Alive"; int beginning = 0, index = 0; StringBuffer strBuffer = new StringBuffer(); while ((index = str.indexOf(subStr1, beginning)) >= 0) { strBuffer.append(str.substring(beginning, index)); strBuffer.append(subStr2); beginning = index + subStr1.length(); } strBuffer.append(str.substring(beginning)); System.out.println("String after replacing substring "+subStr1+" with "+ subStr2 +" = "+strBuffer.toString()); } }