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javalogicconditional-operatorshort-circuiting

Why is the conditional (ternary) operator evaluated in a logical AND when the lhs is false

return super.isAvailable() && expander != null 
    && rightNotLeft ? !expander.isExpandedRight() : expander.isExpandedRight();

My problem was that when expander was null I was getting a null pointer exception. But I didn't think that this should happen since expander!=null is being evaluated to false and since ANDs are being used the entire expression should short circuit and return false.

return super.isAvailable() && expander != null 
    && (rightNotLeft ? !expander.isExpandedRight() : expander.isExpandedRight());

The above code (adding the parentheses) solved the problem. However this does not make sense to me as no matter what happens in the conditional operator there is no way to return true so shouldn't it short circuit?

Thank you for your responses.

Solution

  • This is due to operator precedence. Your condition without explicit parentheses is actually evaluated like

    return (super.isAvailable() && expander != null 
    && rightNotLeft) ? !expander.isExpandedRight() : expander.isExpandedRight();