Using Object's hashCode() and equals() implementations after they have been overriden

Question

Suppose I have:

public class A {
    @Override
    public int hashCode() {
        // some expensive calculation
    }

    @Override
    public boolean equals(Object obj) {
        // some expensive calculation
    }
}

And at some point in my code I wish to have a map with A as the key type using Object's hashCode() and equals() implementations (i.e. two keys of type A will be considered equal if and only if they refer to the same object).

What's the best way to do it?

Use [IdentityHashMap?](https://docs.oracle.com/javase/8/docs/api/java/util/IdentityHashMap.html) — markspace, Feb 16 '16 at 00:59

Sleiman Jneidi · Accepted Answer · 2016-02-16T01:23:29.520

2

You can override methods upon instantiation

A a = new A(){
  @Override
  public int hashCode() {
    return System.identityHashCode(this);
  }
};

Or use an IdentityHashMap which uses System.identityHashCode

edited Feb 16 '16 at 01:23

answered Feb 16 '16 at 01:00

Sleiman Jneidi

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Using Object's hashCode() and equals() implementations after they have been overriden

1 Answers1