UPDATED: 15 May 2014

Are you agree on statement "We can't create key logger in Java". I know most of you say this statement is correct. Because we know that Java can't read anything outside of JVM (Java Virtual Machine). Even I was thinking same but my colleague was searching on the same. He found API called jNativeHook which makes it happen..

jNativeHook Features

• Global Keyboard Listener
• Global Mouse Listener
• Global Mouse Wheel Listener

How it manage to capture key strokes from other application or anywhere in system?
Well jNativeHook using other programming language to capture key strokes and pass it to your application. Its using

• .dll (Dynamic Link Library) for windows.
• .dylib (Xcode Dynamic Library) for mac
• .so (Shared object) for linux

jNativeHook in action

import org.jnativehook.GlobalScreen;
import org.jnativehook.NativeHookException;
import org.jnativehook.keyboard.NativeKeyEvent;
import org.jnativehook.keyboard.NativeKeyListener;
/**
 * @author javaQuery
 * Global Keyboard Listener
 */
public class jNativeHookExample implements NativeKeyListener {

    /* Key Pressed */
    public void nativeKeyPressed(NativeKeyEvent e) {
        System.out.println("Key Pressed: " + NativeKeyEvent.getKeyText(e.getKeyCode()));

        /* Terminate program when one press ESCAPE */
        if (e.getKeyCode() == NativeKeyEvent.VK_ESCAPE) {
            GlobalScreen.unregisterNativeHook();
        }
    }

    /* Key Released */
    public void nativeKeyReleased(NativeKeyEvent e) {
        System.out.println("Key Released: " + NativeKeyEvent.getKeyText(e.getKeyCode()));
    }

    /* I can't find any output from this call */
    public void nativeKeyTyped(NativeKeyEvent e) {
        System.out.println("Key Typed: " + e.getKeyText(e.getKeyCode()));
    }

    public static void main(String[] args) {
        try {
            /* Register jNativeHook */
            GlobalScreen.registerNativeHook();
        } catch (NativeHookException ex) {
            /* Its error */
            System.err.println("There was a problem registering the native hook.");
            System.err.println(ex.getMessage());
            System.exit(1);
        }

        /* Construct the example object and initialze native hook. */
        GlobalScreen.getInstance().addNativeKeyListener(new jNativeHookExample());
    }
}

Known Issues

• The library does not receive events after waking from a sleep state on Unix/Linux.
• Users on Windows may experience a lapse in event data while using Remote Desktop in full screen mode.

Useful Links
Download API: https://code.google.com/p/jnativehook/downloads/list
Examples: https://code.google.com/p/jnativehook/wiki/examples

Check out jNativeHook project home page for more information and details