ContextMenu in Android

Long click on the button to open the menu.
in java class:

public class ContextmenuActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       
        Button b=(Button)findViewById(R.id.button1);
        registerForContextMenu(b);
    }
    //create the menuuu======================
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
            ContextMenuInfo menuInfo) {
        // TODO Auto-generated method stub
        super.onCreateContextMenu(menu, v, menuInfo);
        MenuInflater inflater=getMenuInflater();
        inflater.inflate(R.layout.contextmenu, menu);
   
    }
    //click to each menu======================
      @Override
    public boolean onContextItemSelected(MenuItem item) {
        // TODO Auto-generated method stub
         if(item.getItemId()==R.id.item1)
         {
             System.out.println("item1 clicked");
         }
          if(item.getItemId()==R.id.item2)
         {
             System.out.println("item2 clicked");
         }
          if(item.getItemId()==R.id.item3)
         {
             System.out.println("item3 clicked");
         }
          if(item.getItemId()==R.id.item4)
         {
             System.out.println("item4 clicked");
         }       
        return super.onContextItemSelected(item);
    }}

Context Menu Xml:

< ?xml version="1.0" encoding="utf-8"?> 
< menu xmlns:android="http://schemas.android.com/apk/res/android"> 
    < group android:checkableBehavior="single"> 
    < item android:id="@+id/item1" android:title="Item 1" /> 
    < item android:id="@+id/item2" android:title="Item 2" /> 
    < item android:id="@+id/item3" android:title="Item 3" /> 
    < item android:id="@+id/item4" android:title="Item 4" /> 
    < /group> 
    < /menu> 

in main Xml:

< ?xml version="1.0" encoding="utf-8"?> 
< RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:gravity="center"> 
    < Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button" /> 
< /RelativeLayout>