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December 4, 2007

Command line Java on DalvikVM

Found this very useful when i was trying out the JNI under android (Short Story – Could not get it to work!).

Step #1: Start with a simple java class

package org.apache;



public class HelloWorld {

    public static void main(String[] args) {

        System.out.println("Hello World!");

    }

}

Compile the java class

C:\android\CmdLine>javac -d . -g Helloworld.java

Step #2: Package the generated classes into a temporary jar

C:\android\CmdLine>jar -cvf Temp.jar *

added manifest

adding: Hello.java(in = 0) (out= 0)(stored 0%)

adding: HelloWorld.java(in = 149) (out= 122)(deflated 18%)

adding: org/(in = 0) (out= 0)(stored 0%)

adding: org/apache/(in = 0) (out= 0)(stored 0%)

adding: org/apache/HelloWorld.class(in = 556) (out= 344)(deflated 38%)

Step #3: Use the “dx” tool to generate a classes.dex from our temporary jar.

C:\android\CmdLine>dx --dex --output=c:/android/CmdLine/classes.dex c:/android/CmdLine/Temp.jar

Step #4: Use the “aapt” tool to create a new jar suitable for use with dalvikvm

C:\android\CmdLine>aapt add CmdLine.jar classes.dex

 'classes.dex'...

and push it into a known location on the emulator

C:\android\CmdLine>adb push CmdLine.jar /data

30 KB/s (0 bytes in 481.000s)

Step #5: kick the tires of dalvikvm

C:\android\CmdLine>adb shell

# /system/bin/dalvikvm -Xbootclasspath:/system/framework/core.jar -version

/system/bin/dalvikvm -Xbootclasspath:/system/framework/core.jar -version

DalvikVM version 0.2.0

Copyright (C) 2007 Google, Inc.

Blah blah blah LICENSE blah blah.

Dalvik VM init failed (check log file)

Step #6: Run our code

# /system/bin/dalvikvm -Xbootclasspath:/system/framework/core.jar -classpath /data/CmdLine.jar org.apache.HelloWorld

/system/bin/dalvikvm -Xbootclasspath:/system/framework/core.jar -classpath /data/CmdLine.jar org.apache.HelloWorld

Hello World!



(끝)