this keyword in java

this:

It is a keyword
It is a pre-defined variable
It holds object address
It must be used inside non static area

Displays address using ‘this’:

class Test 
{
	Test() // non static
	{
		System.out.println("In constructor : " + this);
	}
	public static void main(String[] args) 
	{
		new Test();
	}
}

How to access object address:

In non static context: using ‘this’
In static context: using ‘object reference variable’

class Test 
{
	Test()
	{
		System.out.println("In constructor : " + this);
	}
	public static void main(String[] args) 
	{
		Test obj = new Test();
		// System.out.println("In main : " + this);  -> Error : 'this' not allowed in static
		System.out.println("In main : " + obj);
	}
}

Accessing static members:

We access static members (variables or methods) using class name
From any location (static or non static) we using class name
For example..

class Test 
{
	Test()
	{
		System.out.println("From constructor : ");
		Test.fun();
	}
	public static void main(String[] args) 
	{
		Test obj = new Test();
		System.out.println("From main");
		Test.fun();
	}
	static void fun()
	{
		System.out.println("static fun..");
	}
}

How can we access non static members?

Generally non static members need to access using object address
From non static area, we use ‘this’ variable
From static area, we use ‘object reference variable’

class Test 
{
	Test()
	{
		System.out.println("From constructor : ");
		this.fun();
	}
	public static void main(String[] args) 
	{
		Test obj = new Test();
		System.out.println("From main");
		obj.fun();
	}
	void fun()
	{
		System.out.println("static fun..");
	}
}

Check this out:

class Test 
{
	public static void main(String[] args) 
	{
		Test obj = new Test();
		System.out.println("Main");
		obj.m1();
	}
	void m1()
	{
		System.out.println("m1");
		this.m2();
	}
	void m2()
	{
		System.out.println("m2");
		Test.m3();
	}
	static void m3()
	{
		System.out.println("m3");
	}
}