How Does Java Resolve Overloaded Methods When a Null Argument is Passed?

Overload Resolution for Null Arguments in Java

When passing null as an argument to an overloaded method in Java, it's crucial to understand which method will be selected for invocation.

Consider the following example:

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

Two overloaded methods of JOptionPane.showInputDialog exist:

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

Which of these overloads will be called when passing null as the parent parameter?

Answer:

Java resolves the overload based on the principle of "most specific method." In this case, the most specific method is:

showInputDialog(Component parent, Object message)

This rule is derived from the overload resolution process, specifically the step known as "Determining the Method Signature." The compiler searches for the most specific method that can handle the input types (in this case, null and String).

The "more specific" method is determined based on whether one overload's invocation could be passed to another without causing a compile-time type error. In this example, any invocation of the first overload could be passed to the second without an error, but not vice versa.

Hence, when passing null to JOptionPane.showInputDialog, the overload with the Component parent parameter (the most specific method) will be selected for invocation.

The above is the detailed content of How Does Java Resolve Overloaded Methods When a Null Argument is Passed?. For more information, please follow other related articles on the PHP Chinese website!