Java Stream How to - Use class field variable to save calculation for a method reference

Question

We would like to know how to use class field variable to save calculation for a method reference.

Answer

/* w  ww .  j  a  va 2 s .  com*/
import java.util.stream.LongStream;

public class Main {
  public static void main(String...args){
    Accumulator accumulator = new Accumulator();
    LongStream.rangeClosed(1, 100).forEach(accumulator::add);
    System.out.println(accumulator.total); 
  }
}
class Accumulator {
  long total = 0;

  public void add(long value) {
      total += value;
  }
}

The code above generates the following result.