CODEWITHSUNDEEP
javareferenceassertequality
El Ronnoco
El Ronnoco

Reputation: 11912

What is going on with Asserts Equality here?

Found this website to presumably test wannabe developers...

http://www.devchallenge.co.uk/challenge-2

The question is this...

Based on the given code, which of the following tests will return a ‘true’ answer and pass, and which will return a ‘false’ answer and fail?

ArrayList array1 = new ArrayList();
ArrayList array2 = new ArrayList();

array1.add(1);
array1.add(2);
array1.add("Aviva");

array2.add(1);
array2.add(2.0);
array2.add("Aviva");

Asserts
   Equality
      (array1[0],array2[0]);

Asserts
   Equality
      (array1[1],array2[1]);

Asserts
   Equality
      (array1[2],array2[2]);

Apparently the answer is 'Fail', 'Fail', 'Pass'.

I'm not a Java developer - and I am presuming this challenge is in Java (though it isn't stated).

What exactly is Equality doing? Is it checking for the same object or the same value? I know that some objects are interned into the String/Integer pool in Java and so I can understand why the last one is true. But why is the first one not true?

Upvotes: 1

Views: 149

Answers (2)

Kai
Kai

Reputation: 39651

This is not valid Java syntax. You cannot call Asserts Equality ().

As an assert in a JUnit test this has to be Assert.assertEquals(array[0], array2[0]) which would cause comparing two Integers. So this should pass.

So I don't understand your proposed results of that code also. I would say pass, fail, pass is right.

Upvotes: 1

Francis Upton IV
Francis Upton IV

Reputation: 19443

If the scalars are being "auto-boxed" then they will have different object holders, so a tests of == will be false, but the strings will pass the == test since the compiler makes sure the same exact string as a constant is used. If you are considering an .equals() test, then they will all be equal.

Upvotes: 1

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