Dávid,
I don't understand the point of this test, both implementations of anonymous
classes are broken because neither implement equals() or hashCode(), therefore
violating the Map.Entry contract. See PairTest.testEqualsAnonynous().
> > Every instance of Map.Entry equals to itself, but not equals of something
> that is created the same way.
I don't understand what you mean. You can use equals() and hashCode() with a
Java 8 AbstractMap.SimpleEntry and a Pair in either direction because
AbstractMap.SimpleEntry implements the Map.Entry contract correctly, unlike ALL
the tests in this thread. See PairTest.testPairOfAbstractMapSimpleEntry().
Gary
On 2024/09/26 12:39:31 Dávid Szigecsán wrote:
> Well, we both were a bit mistaken.
> I did the following test.
> ```
> @Test
> public void run() {
> Pair pair = Pair.of("a", "b");
> Map.Entry<String, String> entry = new Map.Entry<String, String>() {
> public String getKey() { return "a"; }
> public String getValue() { return "b"; }
> public String setValue(String value) { return null; }
> };
> Map.Entry<String, String> entry2 = new Map.Entry<String, String>() {
> public String getKey() { return "a"; }
> public String getValue() { return "b"; }
> public String setValue(String value) { return null; }
> };
> Assert.assertTrue(pair.equals(entry)); // true
> Assert.assertTrue(pair.equals(entry2)); // true
> Assert.assertTrue(entry.equals(entry)); // true
> Assert.assertTrue(entry2.equals(entry2)); // true
> Assert.assertTrue(entry.equals(entry2)); // false
> Assert.assertTrue(entry.equals(pair)); // false
> }
> ```
> You are right about that it is an interface and it seems it has no default
> implementation, but it does some magic.
> Every instance of Map.Entry equals to itself, but not equals of something
> that is created the same way.
>
>
> Gary D. Gregory <[email protected]> ezt írta (időpont: 2024. szept. 26.,
> Cs, 14:26):
>
> >
> >
> > On 2024/09/26 11:36:49 Dávid Szigecsán wrote:
> > ...
> > > Map.Entry.equals() howewer checks if the other is an instance of the same
> > > class.
> >
> > Dávid,
> >
> > It does not, in Java 8 and 23, the method is abstract and does not define
> > code, but the Javadoc does define expected behavior.
> >
> > I imagine that it was not changed to a default method for compatibility.
> >
> > Gary
> >
> > So if we want them to be equals, we should change the Map.Entry,
> > > that is out of our limit of power. To make it symmetric we could check
> > for
> > > the instances of the same class also (and return false in this case),
> > but I
> > > think we don't want this.
> > >
> > > Dávid
> > >
> > > Alex Tsvetkov <[email protected]> ezt írta (időpont: 2024. szept.
> > 26.,
> > > Cs 13:11):
> > >
> > > > Hi.
> > > >
> > > > I found a bug in the implementation of the method `equals` of class
> > `Pair`.
> > > >
> > > > Implementation must be symmetric. Current implementation is not.
> > > >
> > > > Her test showing the problem:
> > > >
> > > > ```
> > > >
> > > > @Test
> > > > void run() {
> > > > var pair = Pair.of("a", "b");
> > > > var entry = new Map.Entry<String, String>() {
> > > > public String getKey() { return "a"; }
> > > > public String getValue() { return "b"; }
> > > > public String setValue(String value) { return null; }
> > > > };
> > > > assertTrue(pair.equals(entry)); // true
> > > > assertTrue(entry.equals(pair)); // false
> > > > }
> > > > ```
> > > >
> > >
> >
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