Hello World Android!

HelloWorld.java

package com.android.test;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class HelloWorld extends Activity

{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Button button = (Button) findViewById(R.id.Button01);
        button.setOnClickListener(new OnClickListener() {
           @Override
           public void onClick(View v) {
            Toast.makeText(HelloWorld.this, "Hello World", Toast.LENGTH_SHORT).show();
           }
         });       
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<button android:text="Click Me"
 android:id="@+id/Button01"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"></Button>
</LinearLayout>