Returning an element from a list in java

Question

Can you tell me what are the advantages (if there is any advantage) of using getTheLastElement2() instead of getTheLastElement()? I mean why is it necessary to create the reference obj when it is easier just to return the result?

import java.util.ArrayList;
        import java.util.List;

public class Test {
    List list;

    Test(ArrayList list){
        this.list = list;
    }

    public Object getTheLastElement(){
        if (list.isEmpty())
            return null;
        else
            return list.get(list.size()-1);
    }

    public Object getTheLastElement2(){
        Object obj;
        if (list.isEmpty())
            obj = null;
        else
            obj = list.get(list.size()-1);
        return obj;
    }
}

You'll have to return the `size - 1`th element, not just `size`. — Kajal, May 28 '16 at 11:19
You might also like to have a look at http://stackoverflow.com/questions/36707/should-a-function-have-only-one-return-statement which discusses the pros and cons of having a single exit point vs multiple exit points in a function. In your code example I would suggest that `getTheLastElement()` is more readable, and would be even more so without the `else` statement. — mhawke, May 28 '16 at 11:31

Sergey Kalinichenko · Accepted Answer · 2016-05-28T11:25:31.440

2

There is no difference between these two implementations: the obj reference will probably be optimized away.

You do get a slight advantage when debugging the code, because you can set breakpoint on the return statement of getTheLastElement2, and know that it is always going to be hit. This is in contrast with getTheLastElement, where you would need two breakpoints to examine the return value.

Note that else in the first example is redundant:

public Object getTheLastElement(){
    if (list.isEmpty()) {
        return null;
    }
    return list.get(list.size()-1);
}

You could further shrink this to a single ternary expression:

public Object getTheLastElement(){
    return !list.isEmpty() ? list.get(list.size()-1) : null;
}

edited May 28 '16 at 11:25

answered May 28 '16 at 11:21

Sergey Kalinichenko

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Would that else influence the execution time? – webpersistence May 28 '16 at 11:24
@rEx No, it is redundant, and is going to be eliminated by the compiler. In terms of execution speed these all are equal. – Sergey Kalinichenko May 28 '16 at 11:26

score 1 · Answer 2 · answered May 28 '16 at 11:19

1

No, there is no advantage. Also, you should return list.get(list.size()-1)

answered May 28 '16 at 11:19

Priyansh Goel

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Returning an element from a list in java

2 Answers2