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Map myMap = new HashMap();
Integer key = new Integer(5);
String value = "five";
key = new Integer(12); value = "twelve"; myMap.put(key, value);
key = new Integer(20); value = "twenty"; myMap.put(key, value);
key = new Integer(5);
// this is the trick
value = (String) myMap.get(key);
System.out.println(value); // this should print "five"
Though the key that I used is not the same instance of Integer that I used to put the value, I should get the same value that I used when I inserted "five" as a value, and that is because New Integer(5).equals(new Integer(5)) is true (as far as I know). Am I wrong?
If I'm correct then I don't know why the F&/(%&NG HashMap doesn't get me the right values because I overid the equals(Object) method of the classes that I'm using as keys.
You piece of code gives five for me.
If you have a different behaviour, you are probably right thinking overriding the equals method is the source of your problem.
By the way, reading the Java source code is not forbidden and may be instructive.
I (as a developer) can't take the time to study everything everyone has written. If there's one specification that stipulates the way one method in a class works, I SHOULDN'T need to go to ONE IMPLEMENTATION to take a look at the code, I have to trust the specification cause that's what the code should implement anyway (any implementation).
I took a closer look at the API specification and found that (apparently) the AbstractMap will go through the keys and compare them, probably doing a "=="..... it doesn't say it will use the equals(Object) method. So I guess that's the problem.