Java static keyword
The static keyword in java is used for memory management mainly. We can apply java static keyword with variables, methods, blocks and nested class. The static keyword belongs to the class than instance of the class.
The static can be:
1) Java static variable
If you declare any variable as static, it is known static variable.
Advantage of static variable
It makes your program memory efficient (i.e it saves memory).
Understanding problem without static variable
Suppose there are 500 students in my college, now all instance data members will get memory each time when object is created.All student have its unique rollno and name so instance data member is good.Here, college refers to the common property of all objects.If we make it static,this field will get memory only once.
Java static property is shared to all objects.
Example of static variableTest it Now
Output:111 Karan ITS 222 Aryan ITS
Program of counter without static variable
In this example, we have created an instance variable named count which is incremented in the constructor. Since instance variable gets the memory at the time of object creation, each object will have the copy of the instance variable, if it is incremented, it won't reflect to other objects. So each objects will have the value 1 in the count variable.Test it Now
Output:1 1 1
Program of counter by static variable
Output:1 2 3
2) Java static method
If you apply static keyword with any method, it is known as static method.
Example of static methodTest it Now
Output:111 Karan BBDIT 222 Aryan BBDIT 333 Sonoo BBDIT
Another example of static method that performs normal calculationTest it Now
Restrictions for static method
Output:Compile Time Error
Q) why java main method is static?
3) Java static block
Output:static block is invoked Hello main
Ans) Yes, one of the way is static block but in previous version of JDK not in JDK 1.7.Test it Now
Output:static block is invoked (if not JDK7)
In JDK7 and above, output will be:
Output:Error: Main method not found in class A3, please define the main method as: public static void main(String args)