Java bytecode: Difference between revisions

Revision as of 08:57, 23 September 2006

Revision as of 09:04, 23 September 2006

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If executing Java bytecode in a Java virtual machine is not desirable, a developer can also compile Java source code or Java bytecode directly to native machine code with tools such as the [[GCJ|GNU Compiler for Java]].

== Example ==

Consider the following Java code.

<code>

outter: for (int i = 2; i < 1000; i++) {

for (int j = 2; j < i; j++) {

if (i % j == 0)

continue outter;

}

System.out.println (i);

}

</code>

This is probably translated into byte code like (assuming the above was put in a method):

<code>

Code:

0: iconst_2

1: istore_1

2: iload_1

3: sipush 1000

6: if_icmpge 44

9: iconst_2

10: istore_2

11: iload_2

12: iload_1

13: if_icmpge 31

16: iload_1

17: iload_2

18: irem # remainder

19: ifne 25

22: goto 38

25: iinc 2, 1

28: goto 11

31: getstatic #84; //Field java/lang/System.out:Ljava/io/PrintStream;

34: iload_1

35: invokevirtual #85; //Method java/io/PrintStream.println:(I)V

38: iinc 1, 1

41: goto 2

44: return

</code>

==The Java bytecodes==

Line 239 ⟶ 282:

''This list is incomplete.''

== Example ==

Consider the following Java code.

<code>

outter: for (int i = 2; i < 1000; i++) {

for (int j = 2; j < i; j++) {

if (i % j == 0)

continue outter;

}

System.out.println (i);

}

</code>

This is probably translated into byte code like (assuming the above was put in a method):

<code>

Code:

0: iconst_2

1: istore_1

2: iload_1

3: sipush 1000

6: if_icmpge 44

9: iconst_2

10: istore_2

11: iload_2

12: iload_1

13: if_icmpge 31

16: iload_1

17: iload_2

18: irem # remainder

19: ifne 25

22: goto 38

25: iinc 2, 1

28: goto 11

31: getstatic #84; //Field java/lang/System.out:Ljava/io/PrintStream;

34: iload_1

35: invokevirtual #85; //Method java/io/PrintStream.println:(I)V

38: iinc 1, 1

41: goto 2

44: return

</code>

==See also==