Understanding lambdas and/or predicates

Question

I'm completely new to Java 8 and I'm trying to wrap my head around why the last test is false.

@Test
public void predicateTest() {
    Predicate<Boolean> test1 = p -> 1 == 1;
    Predicate<Boolean> test2 = p -> p == (1==1);

    System.out.println("test1 - true: "+test1.test(true));
    System.out.println("test1 - false: "+test1.test(false));
    System.out.println("test2 - true: "+test2.test(true));
    System.out.println("test2 - false: "+test2.test(false));
}

Output:

test1 - true: true

test1 - false: true

test2 - true: true

test2 - false: false

Answer 1

Elaboration

Your first Predicate i.e.

Predicate<Boolean> test1 = p -> 1 == 1;

can be represented as

Predicate<Boolean> test1 = new Predicate<Boolean>() {
    @Override
    public boolean test(Boolean p) {
        return true; // since 1==1 would ways be 'true'
    }
};

So irrespective of what value you pass to the above test method, it would always return true only.

On the other hand, the second Predicate i.e.

Predicate<Boolean> test2 = p -> p == (1==1);

can be represented as

Predicate<Boolean> test2 = new Predicate<Boolean>() {
    @Override
    public boolean test(Boolean p) {
        return p; // since 'p == true' would effectively be 'p'
    }
};

So whatever boolean value you would pass to the above test method, it would be returned as is.

---

And then you can correlate how the method test corresponding to each instance test1 and test2 of the anonymous classes are invoked and what shall be the probable output.