Reference equality for X and Integer

Hi,
my problem is that i'd like to understand why java won't accept this statement at compile time.
Class X { .... }
Class Y {
   doSomething(...) {
      X x1;
      Integer i;
      boolean b = i == x1;
}I absolutly know that this code makes no sense but I don't understand my java won't compile this type of code. The problem is the comparsion of Integer and X but they are both objects so why doesn't it word?
If I use another variable with the type of Y the comparsion would be executed at runtime.
Thanks a lot
Jonny

You are trying to compare references of types that are incompatible.
Here is the relevant part of the Java Spec on == (Section 15.21.3):
"A compile-time error occurs if it is impossible to convert the type of either operand to the type of the other by a casting conversion (5.5). The run-time values of the two operands would necessarily be unequal."
Some other commenter recommended using equals, which of course, will never return true in this case and probably throw a runtime exception anyways.
They might want to re-read my comments in the Topic Java app disobeying 'if' structure abort the importance to understand the difference between == and Object.equals.

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