When an interface lists a method as "optional," you do not need to implement it when defining a class that implements the interface.

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In Java, when a class implements an interface, it must provide implementations for all of the methods declared in the interface, unless the class is declared as abstract. There is no built-in mechanism for marking interface methods as "optional" in the sense that implementing classes can choose to ignore them.

When an Interface Lists a Method as "Optional," You Do