Name: skT88420 Date: 10/27/99


C:\javanew>java -version
java version "1.3beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3beta-O)
Java(TM) HotSpot Client VM (build 1.3beta-O, mixed mode)
Compile the test program using this command line:

javac -target 1.2 -g ClassNameTest.java

Then run the program like this:

java ClassNameTest

Which should cause the following output:

Exception in thread "main" java.lang.NullPointerException
        at ClassNameTest.getMangledClassName(ClassNameTest.java:20)
        at ClassNameTest.main(ClassNameTest.java:36)

Now compile like this:

javac -target 1.1 -g ClassNameTest.java

and rerun the program to obtain this output:

ClassNameTest$JunkClassEditor


Using the javap tool you can see that at instruction #8 there is a difference
between the target 1.2 and target 1.1 code. I take this to indicate a code
generation problem, but I suppose it could be a problem with the JVM if the
instruction at #8 is really correct code.

Code from -target 1.2:

Method java.lang.String getMangledClassName(ClassNameTest.JunkInterface)
   0 aconst_null
   1 aload_1
   2 if_acmpne 7
   5 aconst_null
   6 areturn
   7 aload_1
   8 invokeinterface (args 1) #2 <InterfaceMethod null>
  13 astore_2
  14 aload_2
  15 invokevirtual #3 <Method java.lang.String getName()>
  18 astore_3
  19 aload_2
  20 invokevirtual #4 <Method java.lang.ClassLoader getClassLoader()>
  23 astore 4
  25 new #5 <Class java.lang.StringBuffer>
  28 dup
  29 invokespecial #6 <Method java.lang.StringBuffer()>
  32 aload_3
  33 invokevirtual #7 <Method java.lang.StringBuffer append(java.lang.String)>
  36 ldc #8 <String "Editor">
  38 invokevirtual #7 <Method java.lang.StringBuffer append(java.lang.String)>
  41 invokevirtual #9 <Method java.lang.String toString()>
  44 astore 5
  46 aload 5
  48 areturn


Code from -target 1.1:
Method java.lang.String getMangledClassName(ClassNameTest.JunkInterface)
   0 aconst_null
   1 aload_1
   2 if_acmpne 7
   5 aconst_null
   6 areturn
   7 aload_1
   8 invokevirtual #2 <Method java.lang.Class getClass()>
  11 astore_2
  12 aload_2
  13 invokevirtual #3 <Method java.lang.String getName()>
  16 astore_3
  17 aload_2
  18 invokevirtual #4 <Method java.lang.ClassLoader getClassLoader()>
  21 astore 4
  23 new #5 <Class java.lang.StringBuffer>
  26 dup
  27 invokespecial #6 <Method java.lang.StringBuffer()>
  30 aload_3
  31 invokevirtual #7 <Method java.lang.StringBuffer append(java.lang.String)>
  34 ldc #8 <String "Editor">
  36 invokevirtual #7 <Method java.lang.StringBuffer append(java.lang.String)>
  39 invokevirtual #9 <Method java.lang.String toString()>
  42 astore 5
  44 aload 5
  46 areturn

Here is the program:
//--------Program follows-----------------
public class ClassNameTest
{
   public interface JunkInterface
   {
      public void blahBlahBlah(int j);
   }
   
   public static class JunkClass implements JunkInterface
   {
      public void blahBlahBlah(int j)
      {
         return;
      }
   }
   

   public String getMangledClassName(JunkInterface ai)
   {
      if(null == ai) {
         return null;
      }
      Class itemClass = ai.getClass();
      String className = itemClass.getName();
      ClassLoader cl = itemClass.getClassLoader();
         
      String editorClassName = className + "Editor";
      
      return editorClassName;
   }
   
   public static void main(String args[])
   {
      JunkInterface o = new JunkClass();
      ClassNameTest cnt = new ClassNameTest();
      
      String s = cnt.getMangledClassName(o);
      System.out.println(s);
   }
}
(Review ID: 97134)
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