What methods should go into a java.util.Objects class in JDK 7?

[Goktug Gokdogan]

Similarly, I've previously written reflection-based #clone, #equals, and
#fillRandomData methods working on POJOs. They were useful especially in
testing the data binding codes, ie.  X original = new X();,
  fillRandomData(original);
  mapper.toGUI( clone(original) ); //Clone object so original data can not
be modified
  X rv = new X();
  mapper.fromGUI(rv);
  assertTrue( equals(original, rv) );

But I can not imagine much use in a production code. If other use cases can
be suggested, we could consider putting into Objects class.


On Thu, Sep 10, 2009 at 2:25 AM, Kevin Bourrillion <kevinb at google.com>wrote:

> -1 on reflection-based stuff in the Objects class.
>
> equal() and hashCode() are the only two things we saw fit to include in our
> Objects class, and actually, our hashCode() is identical to
> Arrays.hashCode() (but is varargs).
>
>
> http://google-collections.googlecode.com/svn/trunk/javadoc/com/google/common/base/Objects.html
>
> Please do add the compare() methods to all the rest of the wrapper types;
> we would use those a lot.
>
> When it comes to cloning, I tried very hard once to provide something
> useful -- a "clone any object without knowing its concrete type" method --
> and it was a disaster.  A total mess of reflection, and no one wanted to use
> it anyway.  Cloning in Java is discredited.
>
> So I'm left with only equal() for your new Objects class.  By the way, the
> best implementation is a == b || (a != null && a.equals(b)).
>
>
>
>
> On Wed, Sep 9, 2009 at 2:22 PM, Andrew John Hughes <
> gnu_andrew at member.fsf.org> wrote:
>
>> 2009/9/9 Joe Darcy <Joe.Darcy at sun.com>:
>> > Hello.
>> >
>> > For JDK 7, I think it is high-time the platform included a class like
>> > java.util.Objects to hold commonly-written utility methods.  For
>> example, a
>> > two-argument static equals method that returned true if both arguments
>> are
>> > null, returns false is one argument is null, and otherwise returns the
>> > result of calling arg1.equals(arg2)  (6797535 "Add shared two argument
>> > static equals method to the platform").
>> >
>> > A static hashCode method returning 0 for null and the value of
>> > arg.hashCode() has also been suggested.
>> >
>> > A set of
>> >
>> >   static int compareTo(int, int)
>> >   static int compareTo(long, long)
>> >   ....
>> >
>> > methods probably belongs somewhere in the platform too.
>> >
>> > What other utility methods would have broad enough use and applicability
>> to
>> > go into a common java.util class?
>> >
>> > -Joe
>> >
>>
>> Given you've listed utility methods for two Object methods, equals and
>> hashCode, toString seems an obvious one to handle as well:
>>
>> public static String toString(Object o)
>>  throws IllegalAccessException
>> {
>>  Class<?> c = o.getClass();
>>  StringBuilder b = new StringBuilder(c.getName());
>>  b.append("[");
>>  for (Field f : c.getDeclaredFields())
>>  {
>>    f.setAccessible(true);
>>    b.append(f.getName() + "=" + f.get());
>>    b.append(",");
>>  }
>>  b.replace(b.length() - 1, b.length(), "]");
>>  return b.toString();
>> }
>>
>> Maybe there's also a useful utility implementation of clone too, but I
>> can't think of one offhand.
>> --
>> Andrew :-)
>>
>> Free Java Software Engineer
>> Red Hat, Inc. (http://www.redhat.com)
>>
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>
>
>
> --
> Kevin Bourrillion @ Google
> internal:  http://go/javalibraries
> google-collections.googlecode.com
> google-guice.googlecode.com
>
>
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