want help on "THIS" KEY WORD

[anoop_mig25]

HI FRIENDS I WANT UR HELP REGARDING "THIS" REFERNCE KEY WORD. i know its use to refer present object but i am getting little confuse.

can anyone tell me any way/trick/ how to identifiy to which object "this" keyword refernces .

i am positing 2 codes please tell whether i am wrong or write

first code

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class keyevent1 extends Applet implements KeyListener
{
public void init()
{
requestFocus();  	// to request focus on applet
addKeyListener(this);[B][COLOR="Red"]does "this
" refernce to applet[/COLOR][/B]
}
public void keyPressed(KeyEvent tt)
{
switch(tt.getKeyChar())
{
case ‘r’:
case ‘R’: setBackground(Color.red);break;
case ‘g’:
case ‘G’: setBackground(Color.green);break;
case ‘b’:
case ‘B’: setBackground(Color.blue);break;
case ‘y’:
case ‘Y’: setBackground(Color.yellow);break;
default: setBackground(Color.black);
}
}
public void keyReleased(KeyEvent tt) { }
public void keyTyped(KeyEvent tt) { }
}

second code does keyword "this" in below code refer to object "button1" or "mtextbtn..n"

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Button1 extends JFrame implements ActionListener 
{
	JButton mtextbtn1;
	JButton mtextbtn2;
	JButton mtextbtn3;
	JButton mtextbtn4;
	JButton mtextbtn5;
	
	public Button1() 
	{
		setTitle("BUTTON EXAMPLE");
		JPanel contentpane = (JPanel)getContentPane();
		contentpane.setLayout(new FlowLayout());
		//contentpane.setLayout(new GridLayout(2,3));

		mtextbtn1 = new JButton("Enabled");
		mtextbtn1.setMnemonic('E');
		mtextbtn1.addActionListener(this); [COLOR="Red"]this refers to whom button1 or mtexbtn1[/COLOR]
		contentpane.add(mtextbtn1);
		
		mtextbtn2 = new JButton("Disabled");
		mtextbtn2.setMnemonic('D');
		mtextbtn2.addActionListener(this);
		contentpane.add(mtextbtn2);[COLOR="Red"]this refers to whom button1 or mtexbtn2[/COLOR]

		mtextbtn3 = new JButton("Add");
		mtextbtn3.setMnemonic('A');
		mtextbtn3.addActionListener(this);[COLOR="Red"]this refers to whom button1 or mtexbtn4[/COLOR]
		contentpane.add(mtextbtn3);
		
		mtextbtn4 = new JButton("Fourth");
		mtextbtn4.setMnemonic('F');
		mtextbtn4.addActionListener(this);[COLOR="Red"]this refers to whom button1 or mtexbtn4[/COLOR]
		contentpane.add(mtextbtn4);
		
		mtextbtn5 = new JButton("Fifth");
		mtextbtn5.setMnemonic('T');
		mtextbtn5.addActionListener(this);[COLOR="Red"]this refers to whom button1 or mtexbtn5[/COLOR]
		contentpane.add(mtextbtn5);

		mtextbtn1.setEnabled(true);
		myadapter myapp = new myadapter();
		addWindowListener(myapp);
	}

	

class myadapter extends WindowAdapter 
{
   public void windowClosing(WindowEvent e) 
	{
		System.exit(0);
		}
	}
	
public void actionPerformed(ActionEvent e)
	{
		if(e.getSource() == mtextbtn1) 
		{
		setTitle("First Button Clicked");
		}
		else if (e.getSource() == mtextbtn2)
		{
		setTitle("Second Button Clicked");
		}
		else if (e.getSource() == mtextbtn3) 
		{
		setTitle("Add Button Clicked");
		}
		else if (e.getSource() == mtextbtn4) 
		{
		setTitle("Fourth Button Clicked");
		}
		else if (e.getSource() == mtextbtn5) 
		{
		setTitle("Fifth Button Clicked");
		}
		}

		public static void main(String args[]) 
			{
				Button1 b = new Button1();
				b.setSize(100,100);
				b.setVisible(true);
			}
}

[lovelesh]

In first code: this refers to object of keyevent1 class.
In second code: this refers to object of Button1 class.

The best way to identify this type is:

SySystem.out.println(this.getClass());

[ozzyman]

I think you've confused this for referring to Objects like in JavaScript.

as lovelesh has explained, this refers to the current Class, not the object container.

[anoop_mig25]

In first code: this refers to object of keyevent1 class.
In second code: this refers to object of Button1 class.

The best way to identify this type is:

SySystem.out.println(this.getClass());

I think you've confused this for referring to Objects like in JavaScript.

as lovelesh has explained, this refers to the current Class, not the object container.

thanks both of u for reply but i didn`t get first one . can u explain me a lot dipper although i think i got second one write but it may be an hook so can u please provide me link for tutorial/video link were i can clear my concepts

[ozzyman]

There's not much to it, here's a simple tutorial about the this keyword:

Using the this Keyword (The Java™ Tutorials > Learning the Java Language > Classes and Objects)


As for your program, this is how you dynamically add Actions to buttons:

//declare buttons
private JButton mybutton0 = new JButton();
private JButton mybutton1 = new JButton();
private JButton mybutton2 = new JButton();

//add to list so we can loop through each button
java.util.List<JButton> mybuttons = new java.util.ArrayList<JButton>(3);
mybuttons.add(mybutton0);
mybuttons.add(mybutton1);
mybuttons.add(mybutton2);

//create a loop to add button actions
for (int i=0; i<mybuttons.size(); i++) {
    //adding the button action
    mybuttons.get(i).addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //external method
            mybuttonsAction(i);
        }
    } );
}

Then somewhere else in your class have this method:

public void mybuttonsAction(int actionNo) {
    switch(actionNo) {
        case 0:
            //commands for button0
            break;
        case 1:
            //commands for button1
            break;
        case 2:
            //commands for button2
            break;
        default:
            //unrecognized actionNo
            break;
    }
}