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 an instance of the class.
The static can be:
1) Java static variable
If you declare any variable as static, it is known as a static variable.
Advantages of static variable
It makes your program memory efficient (i.e., it saves memory).
Understanding the problem without static variable
Suppose there are 500 students in my college, now all instance data members will get memory each time when the object is created. All students have its unique rollno and name, so instance data member is good in such case. Here, "college" refers to the common property of all objects. If we make it static, this field will get the memory only once.
Java static property is shared to all objects.
Example of static variableTest it Now
111 Karan ITS 222 Aryan ITS
Program of the 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 other objects. So each object will have the value 1 in the count variable.Test it Now
1 1 1
Program of counter by static variable
As we have mentioned above, static variable will get the memory only once, if any object changes the value of the static variable, it will retain its value.Test it Now
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 a static method that performs a normal calculationTest it Now
Restrictions for the static method
There are two main restrictions for the static method. They are:
Output:Compile Time Error
Q) Why is the Java main method static?
Ans) It is because the object is not required to call a static method. If it were a non-static method, JVM creates an object first then call main() method that will lead the problem of extra memory allocation.
3) Java static block
Example of static blockTest it Now
Output:static block is invoked Hello main
Q) Can we execute a program without main() method?
Ans) No, one of the ways was the static block, but it was possible till JDK 1.6. Since JDK 1.7, it is not possible to execute a java class without the main method.Test it Now
static block is invoked
Since JDK 1.7 and above, output would be:
Error: Main method not found in class A3, please define the main method as: public static void main(String args) or a JavaFX application class must extend javafx.application.Application