Why does the java.util.Set interface not provide a get(Object o) method? [closed]

Answer 1

"I want the exact object instance that is already in the set, not a possibly different object instance where .equals() returns true."

This doesn't make sense. Say you do:

Set s = new Set();
s.Add(new Foo(...));
...
Foo newFoo = ...;

You now do:

s.contains(newFoo)

If you want that to only be true if an object in the set is == newFoo, implement Foo's equals and hashCode with object identity. Or, if you're trying to map multiple equal objects to a canonical original, then a Map may be the right choice.