CODEWITHSUNDEEP
javajava-8method-reference
prior
prior

Reputation: 518

How to Resolve Java Method Reference Ambiguity

Is there a way to get the compiler to choose the static method reference?

This code fails to compile because there are two methods that satisfy this method reference. Is there a way to hint or cast it so that it resolves the static method reference?

public class Number {
  private final int value;

  public Number(int value) {
    this.value = value;
  }

  public Number add(int x) {
    return operate(Number::add, x);  // <---- compile fail here at Number::add
  }

  private Number operate(BiFunction<Number, Integer, Number> function, int x) {
    return function.apply(this, x);
  }

  public static Number add(Number x, int y) {
    return new Number(x.value + y);
  }

}

Upvotes: 3

Views: 4246

Answers (1)

giorgiga
giorgiga

Reputation: 1778

There is no "collision" :)

The issue is that Number::add is ambiguous (the compiler - the one in eclipse, at least - reports that correctly).

The ambiguous code:

BiFunction<Number, Integer, Number> m = Number::add;

could either mean:

BiFunction<Number, Integer, Number> m = (x,y) -> Number.add(x,y);

or:

BiFunction<Number, Integer, Number> m = (x,y) -> x.add(y);

Upvotes: 5

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