public void addElementToTargetProjectClassPath(String element) throws IllegalArgumentException {
  checkIfValidClasspathEntry(element);
  getTargetProjectClasspath();
  if (targetClassPath == null || targetClassPath.isEmpty()) {
    targetClassPath=element;
  }
 else {
    if (targetClassPath.contains(element)) {
      return;
    }
    targetClassPath+=File.pathSeparator + element;
    Properties.CP=targetClassPath;
  }
}

public void addElementToTargetProjectClassPath ( String element ) throws IllegalArgumentException { checkIfValidClasspathEntry ( element ) ; getTargetProjectClasspath ( ) ; if ( targetClassPath == null || targetClassPath . isEmpty ( ) ) { targetClassPath = element ; } else { if ( targetClassPath . contains ( element ) ) { return ; } targetClassPath += File . pathSeparator + element ; Properties . CP = targetClassPath ; } }
add classpath entry to the classpath of the target project
