static keyword in java with examples

we will see about static keyword in java.So static keyword can be associated with:

    Variable
    Method
    Block
    Nested class

Lets go through each one by one.
Static variable:
If any instance variable is declared as static.It is known as static variable.

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    static int countryCounter;

Some points about static variables are:

    Static variable belongs to a class not to a object.
    Static variable are initialized only once in class area at the time of class loading
    All objects share single copy of static variable
    You don’t need to create object to access static variable.You can directly access it using class name.
    Static variable can be accessed by instance java methods also.

If you create a class with two variables, one static, one non static.Non static variable of that class (objects created from that class) gets its own version of that variable. But with the static variable, it belongs to the class, and there is only one. Although any object from that class can reference it.

Example:
Lets take a very simple example.You want to track how many objects you have created.For that you have a static variable in your class.Lets say your class is:
Country.java
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    package org.arpit.java2blog;
    /*
     * @author:Arpit Mandliya
     */
    public class Country {
        //static variable
       static int countryCounter;
        // instance variable
        String name;
        int dummyCounter;
        Country(String name)
        {
            this.name=name;
            countryCounter++;
            dummyCounter++;
        }
        public static void main(String[] args)
        {
            System.out.println(“****************************************”);
            Country india=new Country(“India”);
            System.out.println(“Country Name: “+india.getName());
            System.out.println(“Number of country object created: “+Country.countryCounter);
            System.out.println(“Dummy counter not a static variable: “+india.dummyCounter);
            System.out.println(“****************************************”);
            Country france=new Country(“France”);
            System.out.println(“Country Name: “+france.getName());
            System.out.println(“Number of country object created: “+france.countryCounter);
            System.out.println(“Dummy counter not a static variable: “+france.dummyCounter);
            System.out.println(“****************************************”);
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
    }

Output:
When you run above program,you will get following results:
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    ****************************************
    Country Name: India
    Number of country object created: 1
    Dummy counter not a static variable 1
    ****************************************
    Country Name: France
    Number of country object created: 2
    Dummy counter not a static variable 1
    ****************************************

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