Java Coding Problems

Method reference to an instance method

Let's assume that we are defining the following Comparator for Melon:

public class MelonComparator implements Comparator {  @Override  public int compare(Object m1, Object m2) {    return Integer.compare(((Melon) m1).getWeight(),      ((Melon) m2).getWeight());  }}

Now, we can refer to it as follows:

• No method reference:

MelonComparator mc = new MelonComparator();List<Melon> sorted = melons.stream()  .sorted((Melon m1, Melon m2) -> mc.compare(m1, m2))  .collect(Collectors.toList());

• Method reference:

List<Melon> sorted = melons.stream()  .sorted(mc::compare)  .collect(Collectors.toList());

Of course, we can call Integer.compare() directly as well:

• No method reference:

List<Integer> sorted = melons.stream() .map(m ...