Java simple code line explanation needed

Question

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What is the Java ?: operator called and what does it do?

Hello I have some problems understanding the fallowing code, could anyone help me get this?

private Comparable elementAt( BinaryNode t ) {
    return t == null ? null : t.element;
}

I don't understand what t == null ? null : t.element; means.

gefei got the issue,i didn't ask about the method declaration, or I would have specified that. Downvoting should come with more than that. — Bogdan M., Nov 09 '12 at 13:17
thanks for the helping atempt, but others helped me already. — Bogdan M., Nov 09 '12 at 13:24

score 5 · Accepted Answer · answered Nov 09 '12 at 13:15

5

return t == null ? null : t.element; means

if (t==null)
  return null;
else
  return t.element;

see also http://en.wikipedia.org/wiki/%3F:#Java

answered Nov 09 '12 at 13:15

gefei

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score 3 · Answer 2 · answered Nov 09 '12 at 13:15

It is a standard idiom that avoids a NullPointerException in case t is null. In that case, instead of dereferencing it to get the element, it just returns null.

Some people argue that this is a bad idiom because it only postpones the NPE, but, depending on the exact situation, it could be just what one needs.

score 1 · Answer 3 · answered Nov 09 '12 at 13:15

1

its a ternary operator (in this case checking for null), ternarys can be used instead of if/else statements

answered Nov 09 '12 at 13:15

NimChimpsky

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thanks i will check this 'ternary operator' :). gl – Bogdan M. Nov 09 '12 at 13:20

Java simple code line explanation needed

3 Answers3