In Java 1.4 onwards the function String.replaceAll does this.
For older versions of Java, you can use this instead:
public static String replaceSubString(String source, String pattern, String replace) { if (source!=null) { final int len = pattern.length(); StringBuffer sb = new StringBuffer(); int found = -1; int start = 0; while( (found = source.indexOf(pattern, start) ) != -1) { sb.append(source.substring(start, found)); sb.append(replace); start = found + len; } sb.append(source.substring(start)); return sb.toString(); } else return ""; }