StringTokenizer sTokenizer = new StringTokenizer(expression);
//operations with some of the tokens here
System.out.println(sTokenizer.nextToken());

sTokenizer.nextToken(null)

expression.substring(currentposition)

public static void main(String[] args){
    String expression = "a b c d e";
    StringTokenizer sTokenizer  = new StringTokenizer(expression);
    System.out.println(sTokenizer.nextToken());
    System.out.println(sTokenizer.nextToken(""));
}

a
 b c d e