Which `showInputDialog` Overload is Called with a Null Argument in Java?

Which Method Overload is Invoked with Null as an Argument in Java?

When writing code in Java, it's important to understand how overload resolution works when passing null as an argument. Let's consider this specific scenario:

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

With two potential overloads of showInputDialog:

• showInputDialog(Component parent, Object message)
• showInputDialog(Object message, Object initialSelectionValue)

Which overload will be invoked?

Determining the Most Specific Method

According to Java's overload resolution rules, the "most specific" method is selected. This involves a nuanced analysis of method signatures and applicability.

Resolution in This Case

The first method, showInputDialog(Component parent, Object message), is determined to be more specific in this scenario because:

• The first argument is declared as Component, and null is a valid value for this type.
• The second argument is declared as Object, which allows any type, including null.

In contrast, the second method, showInputDialog(Object message, Object initialSelectionValue), requires both arguments to be non-null.

Therefore, the most specific method, showInputDialog(Component parent, Object message), is invoked. This is consistent with the principle that the method signature should retain its applicability without introducing compile-time errors.

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