I'm trying to understand if there's a reason in the spec for the discrepany between java descriptors and signatures for inner classes. (I'm looking directly at the content of the class files here, but I use javap to illustrate).

( n.b. I have tried this on JDK 1.6.0_33 and 1.7.0_05, both have the same issue when viewed with javap from Java 7 - java 6's javap doesn't seem to show any generic signature info, as per Sean's answer below. )

Update : Thanks to those discussing - my take is

  • The descriptor (which doesn't contain generic information) is correct.
  • The signature (which is an attribute of the method, and does contain generic information) is incorrect. The relevant ConstPool entry for SIGNATURE of the <init> method is " ConstantUTF8[(Ljava/util/list<TE;>)V] "
  • Javap in Java 6 doesn't LOOK at the signature, just the descriptor. (My guess!)

In case anyone wonders, I hit this without using JAVAP, just looking at the class files myself, I am only using javap to show it. (so it's unlikely to be a javap bug).

Consider:

public class InnerClassTest1 {

  public int getX() {
    return new Inner1(new ArrayList<String>()).getX(4);
  }

  public class Inner1 {
    private final List arg;

    public Inner1(List arg) {
        this.arg = arg;
    }....

vs

public class InnerClassTest2 {

   public int getX() {
      return new Inner1(new ArrayList<String>()).getX(4);
   }

   public class Inner1<E> {
    private final List<E> arg;

    public Inner1(List<E> arg) {
        this.arg = arg;
    }.....

If you look at the output of javap -cs on the inner classes, they're surprisingly different!

public org.benf.cfr.tests.InnerClassTest1$Inner1(org.benf.cfr.tests.InnerClassTest1, java.util.List); Signature: (Lorg/benf/cfr/tests/InnerClassTest1;Ljava/util/List;)V

java decompiling .class-file
Edit
Report