Which overload will get selected for null in Java?

Question

If I write this line in Java:

JOptionPane.showInputDialog(null, \"Write something\");

Which method will be called?

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Answer 1

In your particular case the more specific method will be called. In general, though, there are some cases where the method signature can be ambiguous. Consider the following:

public class Main {

    public static void main(String[] args) {
        Main m = new Main();
        m.testNullArgument(null);
    }

    private void testNullArgument( Object o )
    {
        System.out.println("An Object was passed...");
    }

    private void testNullArgument( Integer i )
    {
        System.out.println("An Integer was passed...");
    }

    private void testNullArgument( String s )
    {
        System.out.println("A String was passed...");
    }
}

In this case, the compiler can't decide between the method that takes an Integer and the method that takes a String. When I try to compile that, I get

reference to testNullArgument is ambiguous, both method testNullArgument(java.lang.Integer) in testnullargument.Main and method testNullArgument(java.lang.String) in testnullargument.Main match