public static String replace(String str,String old_str,String new_str){
  int o=0;
  StringBuilder buf=new StringBuilder();
  for (int i=str.indexOf(old_str); i > -1; i=str.indexOf(old_str,i + 1)) {
    if (i > o) {
      buf.append(str.substring(o,i));
    }
    buf.append(new_str);
    o=i + old_str.length();
  }
  buf.append(str.substring(o,str.length()));
  return buf.toString();
}

public static String replace ( String str , String old_str , String new_str ) { int o = 0 ; StringBuilder buf = new StringBuilder ( ) ; for ( int i = str . indexOf ( old_str ) ; i > - 1 ; i = str . indexOf ( old_str , i + 1 ) ) { if ( i > o ) { buf . append ( str . substring ( o , i ) ) ; } buf . append ( new_str ) ; o = i + old_str . length ( ) ; } buf . append ( str . substring ( o , str . length ( ) ) ) ; return buf . toString ( ) ; }
replaces all occurrences of old_str in str with new_str
