Why is an int-to-Object comparison valid in Java 7, but not in Java 8?

Question

Java 7 applies autoboxing to the int.

 private boolean compare(java.lang.Object, int);
   Code:
      0: aload_1
      1: iload_2
      2: invokestatic  #2       // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
      5: if_acmpne     12
      8: iconst_1
      9: goto          13
     12: iconst_0
     13: ireturn

I created this with build 1.7.0_71-b14

EDIT:

This behaviour was recognized and treated as bug by Oracle:
JDK-8013357: Javac accepts erroneous binary comparison operations

Relevant JLS section is 15.21. Javac seems to treat this as a
reference comparison, but a reference comparison is only allowed when
BOTH operands are reference types.

…
The type rules for binary comparisons in JLS Section 15.21 will now be
correctly enforced by javac. Since JDK5, javac has accepted some
programs with Object-primitive comparisons that are incorrectly typed
according to JLS 15.21. These comparisons will now be correctly
identified as type errors.

Leave a Comment Cancel reply