jvm spec does not define certainly which methods cause the class initialization

Name: szC45993 Date: 06/02/98



The revised jvm spec says:
 
"2.16.4 Initialization

Initialization of a class consists of executing its static initializers (?2.11) and the initializers for
static fields (?2.9.2) declared in the class. Initialization of an interface consists of executing the
initializers for fields declared in the interface (?2.13.4).

Before a class is initialized, its direct superclass must be initialized, but interfaces implemented by
the class need not be initialized. Similarly, the superinterfaces of an interface need not be
initialized before the interface is initialized.

A class or interface type T will be initialized immediately before one of the following occurs:

   T is a class and an instance of T is created.
   T is a class and a static method of T is invoked.
   A non-constant static field of T is used or assigned. A constant field is one that is (explicitly
   or implicitly) both final and static, and that is initialized with the value of a
   compile-time constant expression. A reference to such a field must be resolved at compile
   time to a copy of the compile-time constant value, so uses of such a field never cause
   initialization.

Invocation of certain reflective methods in class java.lang.Class and in package
java.lang.reflect also causes class or interface initialization."

The list of these reflective methods should be defined certainly.
In another way, it contradicts to the main principle of java which sounds
as "compile once and use everywhere".

The test below shows that jdk1.2b4H does not provide the class
initialization at the java.lang.reflect package method Array.newInstance()
use but, for example, the jdk1.2b3A jvm provides class initialization
in this case:


novo7% setenv CLASSPATH /export/home1/JAVA/tmp/../classes:/export/ld22/java/oul/JT20/javatest.jar:/export/home1/JAVA/workdir4/classes:/export/ld22/java/gvv/JT20/classes
novo7% /export/ld14/java/dest/jdk1.2b4H/solaris/bin/java -verify javasoft.sqe.tests.vm.concepts.execution080.execution08001.execution08001
execution08001b.iii =333
execution08001b.iii =333
novo7% echo $status
97
novo7% /export/ld14/java/dest/jdk1.2b3A/solaris/bin/java -verify javasoft.sqe.tests.vm.concepts.execution080.execution08001.execution08001
execution08001b.iii =333
execution08001b.iii =777
novo7% echo $status
95
novo7%



SOURCE:


--------------------- execution08001.java
//File: @(#)execution08001.java 1.3 98/04/14
//Copyright 04/14/98 Sun Microsystems, Inc. All Rights Reserved

package javasoft.sqe.tests.vm.concepts.execution080.execution08001;

import java.io.PrintStream;
import java.lang.reflect.Array;

class execution08001b {

   static int iii = 333;

}

class execution08001a {

   static {
execution08001b.iii = 777;
  }

}

public class execution08001 {

   public static int run(String argv[], PrintStream out) {
String cs = null;
        try {
int dim[] = {3, 5, 7};

out.println("execution08001b.iii ="+execution08001b.iii);
if (execution08001b.iii != 333) return 2;

Object ob = java.lang.reflect.Array.newInstance( execution08001a[][][][][][][].class, dim );

out.println("execution08001b.iii ="+execution08001b.iii);
if (execution08001b.iii != 777) return 2;

        } catch (Throwable e) {
out.println(e);
            return 2;
        }

        return 0;
  }

  public static void main(String argv[]) {
  System.exit(run(argv, System.out) + 95/*STATUS_TEMP*/);
  }

}
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Hook 5(hook5): test

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