can you teach me " this " keywords second use ?

[naved momin]

hi , i know that " this " keyword or reference is used for two ways

1. to solve the conflict between instance variable(class variable ) and local variable. 
2.to pass the current object as a parameter to another method .

i had understand the first one but i didnt understand the second one , i have google it but didnt find what i was looking for , so please any one here can teach me the second use of " this " keyword
with a simple and sweet " sample program " as i m just a java beginer , just 2 weeks ago i had started learning java.
thanksss.

[Bernhard Haeussermann]

What you need to grasp is that the "this" keyword in a Java program always refers to the object on which the method you're currently in was called (the callee of the method).

So to illustrate with the help of an example, suppose that you have a Shape class with a getRenderer() method, where getRenderer() returns a Renderer object that can draw the shape onto the screen.
Suppose further that the Renderer class has a constructor that takes as a parameter the Shape object that it should draw. Then the getRenderer() method of the Shape class might look like this:

public Renderer getRenderer()
{
    return new Renderer(this);
}

So this method returns a new Renderer object that draws the Shape object on which the getRenderer() method was called (this).

[Jesper de Jong]

There is another use of the this keyword that you did not yet mention. Watch this:

public class Example {
    public Example(String s) {
        System.out.println("Hello " + s);
    }

    public Example() {
        this("World");
    }
}

You can use it in constructors to call one of the other constructors in the class.

[naved momin]

Jesper de Jong wrote:There is another use of the this keyword that you did not yet mention. Watch this:

public class Example {
    public Example(String s) {
        System.out.println("Hello " + s);
    }

    public Example() {
        this("World");
    }
}

You can use it in constructors to call one of the other constructors in the class.

thanks ..can you also explain me

2.to pass the current object as a parameter to another method .  

i didnt understand . properly yet .

[Campbell Ritchie]

Try serialisation:

import java.io.Serializable;
import java.io.ObjectOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.FileOutputStream;

public class Foo implements Serializable
{
 . . .
    public void serialise(String fileName)  
    {  
        try  
        {  
             ObjectOutputStream oos = new ObjectOutputStream(  
                        new FileOutputStream(new File(fileName)));  
             try  
             {  
                  oos.writeObject(this);  
             }  
             finally  
             {  
                  oos.close();  
             }  
        }  
        catch (FileNotFoundException fnf)  
        {  
             fnf.printStackTrace();  
        }  
        catch (IOException ioe)  
        {  
             ioe.printStackTrace();  
        }  
    }  
}

In the case of this serialise method, you are passing the whole object to the writeObject() method with the this keyword.

[Jesper de Jong]

naved momin wrote:thanks ..can you also explain me

2.to pass the current object as a parameter to another method .  

i didnt understand . properly yet .

That is what Bernhard explained above.

You can regard this as a kind of special variable, that refers to the object that the currently running method was called on. Here is another example:

public class Example {
    private String name;

    public Example(String name) {
        this.name = name;
    }

    public void methodOne() {
        // Pass the current object (this) to methodTwo
        methodTwo(this);
    }

    public static void methodTwo(Example e) {
        System.out.println(e.name);
    }

    public static void main(String[] args) {
        Example example = new Example("Jesper");
        example.methodOne();
    }
}

[naved momin]

Jesper de Jong wrote:

naved momin wrote:thanks ..can you also explain me

2.to pass the current object as a parameter to another method .  

i didnt understand . properly yet .

That is what Bernhard explained above.

You can regard this as a kind of special variable, that refers to the object that the currently running method was called on. Here is another example:

public class Example {
    private String name;

    public Example(String name) {
        this.name = name;
    }

    public void methodOne() {
        // Pass the current object (this) to methodTwo
        methodTwo(this);
    }

    public static void methodTwo(Example e) {
        System.out.println(e.name);
    }

    public static void main(String[] args) {
        Example example = new Example("Jesper");
        example.methodOne();
    }
}

now 80% is clear , but i didnt understand what do you mean by

(this) refers to the object that the currently running method was called on.

what is hapening over here is we have created two reference variable i.e e and example which points to the same object i.e " new Example() ", and we are calling methodOne() in which we have specified

 methodTwo(this);

but what does " this " is here ...do we are passing "example reference-variable " here to " another reference-variable e " as an argument .

[Rob Spoor]

You can compare "this" inside an object to yourself talking about "me".

[Jesper de Jong]

When you call a (non-static) method, you always call it on some object. Look at the main method in my example:

Example example = new Example("Jesper");
example.methodOne();

In the second line, we are calling methodOne on example. When we then go to methodOne, then inside the method this will refer to the Example object that methodOne was called on.

To translate it to human language, using Rob's suggestion:

Line 19: Main says: "example, execute methodOne!"
Line 10: example now gets to methodOne, and it says: "methodTwo, execute, I'm passing you myself (this)!"

[Shubham Chhabra]

hello to all,
'this' keyword has only one meaning that it has the address of currently calling object or intance. Because it stores the address of currently calling object so it has multiple uses which can be.....we can initilize the fields, this can also be passed in constructors as a parameter....or in some method...etc
i will show you example which will represent the applications of 'this' keyword..




1)
class A
{
int a,b;
public void set()
{
this.a=5;
this.b=6;
}
}
class B
{
public static void main(String s[])
{
A obj=new A();
obj.set();
System.out.println(obj.a+""+obj.b)
}
}