Boolean references are null

Question

Can anyone explain why this code results in the below output?

@Test
public void testBooleanArray() {
    Boolean[] ab = new Boolean[]{a, b};

    a = new Boolean(true);
    b = new Boolean(false);

    for(Boolean x : ab) {
        System.out.println(x);
    }
}

Result:

null
null

Should the array ab not holds pointers to object a and object b, and therefore output:

true
false

Answer 1

a = new Boolean(true);
b = new Boolean(false);

This does not change the objects that a and b were pointing to(the elements in the array). It points them to new objects.

It is not modfying the array

To illustrate:

Boolean a = new Boolean(true);
Boolean b = new Boolean(false);
Boolean c = a;
Boolean d = b;
a = new Boolean(false);
b = new Boolean(true);

c and d will still be true/false respectively. This is the same thing that is happening with the array, except your array reference isn't named the same way.

Answer 2

You have to initialize your booleans before assigning them.

Boolean[] ab = new Boolean[]{a, b};

a = new Boolean(true);
b = new Boolean(false);

to

a = new Boolean(true);
b = new Boolean(false);

Boolean[] ab = new Boolean[]{a, b};

This is before with Objects, you copy the reference to the object, and with new statement, you create a new object, the first a,b were null when assigning.