The static keyword is a non – access modifier in Java which can be used for variables, methods, and block of code. Static variables in Java belong to the class i.e it is initialized only once at the start of the execution. By using static variables a single copy is shared among all the instances of the class, and they can be accessed directly by class name and don’t require any instance. The Static method similarly belongs to the class and not the instance and it can access only static variables but not non-static variables.
Example 1: static methods can access static variables.
// Java program to check accessibility // of static variables inside // static methods class GFG {
// declaring variable 'a' as static
static int a = 5 ;
// main is also a static type
public static void main(String args[])
{
// accessing value of
// static variable
System.out.println( "Static variable:" + a);
}
} |
Static variable:5
Example 2: We cannot access non-static variables inside a static method.
// Java program to check accessibility // of non - static variables inside // static methods class GFG {
// declaring variable 'a' as non - static
int a = 5 ;
// main is also a static type
public static void main(String args[])
{
// accessing value of
// non - static variable
System.out.println( "Non - Static variable:" + a);
}
} |
Output
prog.java:16: error: non-static variable a cannot be referenced from a static context System.out.println("Non - Static variable:" + a); ^ 1 error
Example 3:
// Java Program to demonstrate the accessibility // of static and non-static variables // by static method class Student {
// initialized to zero
int a;
// initialized to zero when class is loaded
// but not for each object created.
static int b;
// Constructor
Student()
{
// incrementing static variable b
b++;
}
// method for printing
public void printData()
{
System.out.println( "Value of a = " + a);
System.out.println( "Value of b = " + b);
}
/*public static void increment(){
a++;
}*/
} // Driver class class GFG {
// main is a static block
public static void main(String args[])
{
// creating instance
Student s1 = new Student();
s1.printData();
// directly accessing variable 'b'
// by class name because it is static
Student.b++;
s1.printData();
}
} |
Value of a = 0 Value of b = 1 Value of a = 0 Value of b = 2
In the above program if we remove comments of the increment method then an error will be raised because the increment method is static and variable a is non-static and we already know static methods cannot access non – static variables.