Difference between class variables and instance variables in Java
Variables are used in Java to store data. There are two types of data variables: Class level variables and Instance level variables.
Instance level variables
An instance variable is individually created for a single object of a class. Suppose that there are two objects, object1 and object2, of a single class, and both objects have an integer variable named count. If the user changes object1’s count, it will not change object2’s count.
The code below is an example of the phenomena explained above.
class example {int count; //instance level variablepublic static void main(String[] args) {example obj1 = new example();example obj2 = new example();obj1.count=5;obj2.count=5;obj1.count++; //change in object1's countSystem.out.println(obj1.count);System.out.println(obj2.count);}}
Class level variables
Class variables are shared between all objects. Changing the variable’s data through one object will change the data for all the objects. This is done by using the word static before declaring the data type. The following code explains this.
class example {static int count; //class level variablepublic static void main(String[] args) {example obj1 = new example();example obj2 = new example();obj1.count=5;obj2.count=5;obj1.count++; //change in object1's countSystem.out.println(obj1.count);System.out.println(obj2.count);}}
As you may have noticed, the same code with the word
staticchanges the implementation. Updating object1’s count changes object2’s count as well.
Free Resources
