Debug / Standard build of Java application

Question

Greetings,

I'm using embedded java, I write the application to a low resource device. One of the problems I get is when the code crashes the device stops. I can get a little information from it with some logging that I've added. (Simple print statements)

This logging cannot remain in the application due to memory constraints.

I was wondering does anyone know is there a flag I can pass to the JVM to state if its a debug or standard compilation I require.

I'd like for the print statements to be included if its a debug build, if it is a standard build to remove the print statements. I ask because I've to constantly cut and paste the statements etc. (IT's a pain)

Thanks

Answer 1

You can make use of the fact that if (constant) is optimized by the compiler.

Make a global variable somewhere called DEBUG:

public static final boolean DEBUG = true;

and then do your logging like so:

if (DEBUG) {
    System.out.println("Debug");
}

To disable debugging, simply change DEBUG to false, and all of the logging statements will be optimized away by the compiler. You can verify this by looking at the generated bytecode with javap -c.

For example:

class DebugTest {
    public static final boolean DEBUG = true;
    public static void main(String[] args) {
        if (DEBUG) {
            int a = 10;
            System.out.println("a = " + a);
        }
    }
}

is compiled as:

Compiled from "DebugTest.java"
class DebugTest extends java.lang.Object{
public static final boolean DEBUG;

DebugTest();
  Code:
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   bipush  10
   2:   istore_1
   3:   getstatic   #2; //Field java/lang/System.out:Ljava/io/PrintStream;
   6:   new #3; //class java/lang/StringBuilder
   9:   dup
   10:  invokespecial   #4; //Method java/lang/StringBuilder."":()V
   13:  ldc #5; //String a = 
   15:  invokevirtual   #6; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   18:  iload_1
   19:  invokevirtual   #7; //Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
   22:  invokevirtual   #8; //Method java/lang/StringBuilder.toString:()Ljava/lang/String;
   25:  invokevirtual   #9; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
   28:  return

}

Changing DEBUG to false yields:

Compiled from "DebugTest.java"
class DebugTest extends java.lang.Object{
public static final boolean DEBUG;

DebugTest();
  Code:
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   return

}