How to initialize instance variables in java

What you will learn here about instance variables in java

• How to initialize instance variables in java

In java, we can initialize instance variables in 5 ways and those are listed below

1. instance variable initialization at the time of declaration
2. initialize instance variables using constructor
3. instance variable initialization using object
4. instance variable initialization using setter method
5. instance variable initialization using instance initialization block

1)instance variable initialization at the time of declaration

The example of initializing instance variable at the time of declaration is given below.

public class IIB 
{
	//instance variable initialization  at time of declaration
	String name="John";
	int age=10;
	
	public static void main(String[] args) 
	{
	}

}

2)initialize instance variables using constructor

The example of initializing instance variable using constructor is given below.

public class IIB {

	String name;
	int age;
	
	public IIB() 
	{
	}

	public IIB(String name, int age) 
	{
		this.name = name;
		this.age = age;
	}

	public static void main(String[] args) 
	{
		//instance variable initialization using constructor
		IIB obj=new IIB("John",10);
		
	}

}

3)instance variable initialization using object

The example of initializing instance variable using object is given below.

public class IIB {

	String name;
	int age;

	public static void main(String[] args) 
	{
		IIB obj=new IIB();
		
		//instance variable initialization using object
		obj.name="John";
		obj.age=10;
		
	}

}

4)instance variable initialization using setter method

The example of initializing instance variable using setter method is given below.

public class IIB {

	String name;
	int age;

	public void setName(String name) {
		this.name = name;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public static void main(String[] args) 
	{
		IIB obj=new IIB();
		
		//instance variable initialization using setter methods
		obj.setName("John");
		obj.setAge(10);
	}

}

5)instance variable initialization using instance initialization block

The example of initializing instance variable using instance initialization block is given below.

public class IIB {

	String name;
	int age;
	
	//instance variable initialization using instance initialization block

	{
		name="John";
		age=10;
	}

	public static void main(String[] args) 
	{		
	}

}