Class variable in Java

m isn't static. That means that you have a different variable for each instance.

When you execute new C3();,

• you create a new instance of the class C3,
• you increment the static variable n (shared by all instances)
• you create a new variable m, initialized to 0,
• and you increment m but only for your new instance.

n is a static variable, thus all instances(c1 and c2 in this case) of the class share its data, where as m isn't a static variable, that means, each instance gets its own value of m

 //initial vals n=0 m=0;
  C3 c1 = new C3(); 
 //value of n is 1 value of m is 1   
 c1.display();


//initial values n=0, m=1(as c1 just incremented n which is static and c2 will now inc      n's current value(which is 1))    
C3 c2 = new C3(); 
//value of n is 2 value of m is 1 
c1.display(); 
c2.display();  

n is a static variable, as a result its scope is the class, not the instance.

m, on the other hand, is an instance variable and only has an existence within an instance.

As a result, each time you initialize a new C3(), m is set to 1 (since it is a new m), but n gets incremented each time (since all instances share it).

For c1 and c2, only one n is available since n is static.But both will b ehaving separate m's since m is not static.

C3 c1 = new C3(); now m=1 and n=1 (m belongs to c1 and n belongs to class) C3 c2 = new C3(); now m=1 and n=2 (m belongs to c1 and n belongs to class)

Every object you instantiate will have m = 1 because m is an instance variable. n, on the other hand, is a class variable. Every object you instantiate will increase the n by 1.

In your case, n will count how many objects you have created.

class C3 {
public static int n = 0; //static or class variable, n does not become 0 after every new instance
public int m = 0; //instance variable, m becomes 0 for every instance

public C3() {
    n++; //n becomes the "last value the class had for n" + 1
    m++; //m becomes 1
}

public void display() {
    System.out.println(n + " " + m);}
}

}

Always look at a static variable as a class variable, so you will only instance it with 0 the first time.