Java Class Variable Example

Java Class Variable Example

Author: Ramesh Fadatare

Core Java Examples

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A class variable is any field declared with the static modifier; this tells the compiler that there is exactly one copy of this variable in existence, regardless of how many times the class has been instantiated.

Java Class Variable Example

Consider these are 100 students in a college named "ABC", each student have their own unique roll number and name but the college remains the same among all the 100 students. The college field is declared as static so it can occupy memory only once.

package net.javaguides.corejava.variables;

public class StaticVariableExample {
    public static void main(String[] args) {
        Student student = new Student(100, "Student 1");
        Student student2 = new Student(101, "Student 2");
        Student student3 = new Student(102, "Student 3");
        Student student4 = new Student(103, "Student 4");

        System.out.println(" ------------ Student 1 -------------");
        System.out.println(student.toString());
        System.out.println(student2.toString());
        System.out.println(student3.toString());
        System.out.println(student4.toString());
    }
}

class Student {
    private int rollNo;
    private String name;
    private static String college = "ABC"; // static variable
    public Student(int rollNo, String name) {
        super();
        this.rollNo = rollNo;
        this.name = name;
    }
    @Override
    public String toString() {
        return "Student [rollNo=" + rollNo + ", name=" + name + ", college=" + college + "]";
    }
}

Output:

Student [rollNo=100, name=Student 1, college=ABC]
Student [rollNo=101, name=Student 2, college=ABC]
Student [rollNo=102, name=Student 3, college=ABC]
Student [rollNo=103, name=Student 4, college=ABC]

Note that, all the students have the same college "ABC".

Related Examples

Reference

Variables in Java

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