Java 8 default method interface override Object equals method [duplicate]

Question

public interface Table<T> {

    @Overrride
    default boolean equals(Object other) {
        //do something and return true/false
    }
}

Why does the above code has compilation error of "java: default method equals in interface Table overrides a member of java.lang.Object"? Can't we override hashCode and equals method using interface default method, presumably I have methods in the same interface to determine the equality of the object implementing this interface?

Steven Schlansker · Accepted Answer · 2015-07-14 00:25:03Z

20

No. Classes with implementations always win over default methods, so having a default hashCode or equals can never be invoked and therefore is forbidden.

edited Jul 14, 2015 at 0:25

answered Jan 19, 2015 at 6:48

Steven Schlansker

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2 Comments

Holger Over a year ago

Not only implementations win over default methods. Any declaration made in a non-interface class (i.e. within the superclass hierarchy) wins, even if it is declared abstract.

Gregory Bishop Over a year ago

Agree with Holger, this is a bug. If I know I have interface methods and a reasonable toString default implementation calling those methods is possible, I should be allowed to declare on in an interface. Unsure what should happen if multiple interfaces declare default implementations, what happens now?

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