Static Variables in Java

In Java, when a variable is declared with the static keyword. Then, a single variable is created and shared among all the objects at the class level. Static variables are, essentially, global variables. All instances of the class share the same static variable. These are the main scenarios when we use the static variable most of the time:

• Storing constant values or default values that can be used across different instances.
• The Static variable is used to store the data of class instances. To record the number of times a class instance is created.

Important points:

• Class-Level: We can create static variables at the class level only.
• Shared Among Objects: The static blocks and static variables are executed in the order they are present in a program. It means if a static variable is modified by any instance, the changes will show in all other instances.
• Accessed through Class Name: Static variables can be called directly with the help of a class only; we do not need to create an object for the class in this.
• Initialization Order: The static variables are initialized before the static blocks and when the static method or block refers to a static variable, then it will use its initialized value.

Example: This example demonstrates how to use a static variable among different methods.

class Geeks
{
    // static variable
    static int a = m1();

    // static block
    static
    {
        System.out.println("Inside static block");
    }

    // static method
    static int m1()
    {
        System.out.println("from m1");
        return 20;
    }

    // static method(main)
    public static void main(String[] args)
    {
        System.out.println("Value of a : " + a);
        System.out.println("from main");
    }
}

from m1
Inside static block
Value of a : 20
from main

Explanation:

• We use the static variable which store the value which is calculated by the m1() method.
• When the class is loaded, static members are initialized first.
• m1() method is called and print the message.
• Then all static variables are initialized and the static block is executed.

Difference Between Static Variable and Instance Variable

Related articles: Are Static Local Variables Allowed in Java?