VM does not check if a final field is initialized twice

Name: akC45999 Date: 04/01/99



The chapter 2.9.1 Field Modifiers of the revised JVMS reads:

A field can be declared final, in which case its declarator must include a
variable initializer (?2.9.2). Both class and instance variables (static and
non-static fields) may be declared final. Once a final field has been
initialized, it always contains the same value.

The test below shows that VM does not check neither if a final field
is initialized nor if it always contains the same value.

------------------------------ test.java ----------------------------

import java.io.PrintStream;

public class test {

  public static void main(String a[]) {

BadClass.someMethod();
System.out.println("Bad");
  }
}

---------------------------- BadClass.jasm --------------------------

public class BadClass
{

static final Field finalField:I;

public static Method someMethod:"()V"
stack 1 locals 0
{
iconst_0;
putstatic Field finalField:"I";
return;
}
}

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novo48% java -fullversion
java full version "JDK-1.2-V"
novo48% java test
Bad

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Name: akC45999 Date: 04/01/99



There is more suitable test case:

------------------------------ test.java ----------------------------

import java.io.PrintStream;

public class test {

  public static void main(String a[]) {

BadClass.someMethod(1);
System.out.println("finalField = " + BadClass.finalField);
BadClass.someMethod(2);
System.out.println("finalField = " + BadClass.finalField);
  }
}

---------------------------- BadClass.jasm --------------------------

public class BadClass
{

static final Field finalField:I;

public static Method someMethod:"(I)V"
stack 1 locals 1
{
iload_0;
putstatic Field finalField:"I";
return;
}
}

---------------------------------------------------------------------

novo48% java test
finalField = 1
finalField = 2

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