RFR: 8324718: Add a static function to java.util.Objects to simplify object equality checks [v6]

[Chen Liang]

On Sat, 27 Jan 2024 07:52:56 GMT, David Alayachew <duke at openjdk.org> wrote:

>> Adding a function to Objects in order to facilitate equality checking and enhance readability. You simply specify the 2 objects that you want to check for equality, and then provide the functions which will be used to provide the values that we will check for equality.
>
> David Alayachew has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rather than reiterating the precondition, let's explain why the method failed

It can be used for general classes. See an example:

public class Stuff {
  public int a, b;
  private static final MethodHandle EQUALS;

  static {
    var lookup = MethodHandles.lookup();
    try {
      EQUALS = ObjectMethods.bootstrap(lookup, "equals", MethodHandle.class, "",
          lookup.findGetter(Stuff.class, "a", int.class),
          lookup.findGetter(Stuff.class, "b", int.class));
    } catch (ReflectiveOperationException ex) {
      throw new ExceptionInInitializerError(ex);
    }
  }

  public boolean equals(Object o) {
    return EQUALS.invokeExact(this, o);
  }
}

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PR Comment: https://git.openjdk.org/jdk/pull/17603#issuecomment-1913227054