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.
// Java program to demonstrate execution
// of static blocks and variables
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");
}
}
// Java program to demonstrate execution// of static blocks and variablesclass 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"); }}Output
from m1 Inside static block Value of a : 20 from main
Explanation: In the above Java program, we use the static variable which store the value which is calculated by the m1() method.
Difference Between Static Variable and Instance Variable
Aspect | Static Variable | Instance Variable |
|---|---|---|
Definition | The static variable is is belong to the class and It shared the same instance in all the reference where it is used. | The instance variable is belong to the instance of a class (object). |
Memory | The static variable is allocated on the time of class loading in the memory only once. | The instance variable is created when we create an object of a class. |
Modification | If we update the value of the static variable it will reflect to all the instances where it is In use. | The instance variable has the separate copies in each of it's instances. |
Access | We can directly access it without creating an object of a class. | The instance variable is only access via object of the class. |
Scope | The scope of the static variable is in the entire class. We can access through all the instances of the class. | It's scopeis limited to the specific instance of the defined class. |
Related articles: Are Static Local Variables Allowed in Java?
