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JAVA #05 – Variables in Java

What are variables?

A temporary holding area of memory in which data can be store (also called operand). Variables in Java behave the same way like most of other object oriented programming languages.

Local variables

  • Local variables are declared in methods, constructors, or blocks.
  • Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor or block.
  • Access modifiers cannot be used for local variables.
  • Local variables are visible only within the declared method, constructor or block.
  • Local variables are implemented at stack level internally.
  • There is no default value for local variables so local variables should be declared and an initial value should be assigned before the first use.

Example:

Here, age is a local variable. This is defined inside pupAge() method and its scope is limited to this method only.

public class Test{
	public void aliAge(){
		int age = 0;
		age = age + 7;
		System.out.println("Ali age is : " + age);
	}

	public static void main(String args[]){
		Test test = new Test();
		test.aliAge();
	}
}

 

Some basic datatypes in Java and its values declaration.

  1. float 10.6756567f
  2. int   16,123
  3. String   “Ali Khan”
  4. byte   10101010111
  5. long 12379873547912
  6. short 0-255
  7. boolean true,false
  8. char ‘A’
  9. double 45.5675675687345

 

Instance variables:

  • Instance variables are those variables which holds instance of any object.
  • When a space is allocated for an object in the heap, a slot for each instance variable value is created.
  • Instance variables are usually initialized by using ‘new’ keyword.
  • If an instance variable is declared in class, it can have access modifier. Otherwise it doesn’t need access modifier in Java programming language.

Example:

import java.io.*;

public class Employee{
	// this instance variable is visible for any child class.
	public String name;

	// salary  variable is visible in Employee class only.
	private double salary;

	// The name variable is assigned in the constructor.
	public Employee (String empName){
		name = empName;
	}

	// The salary variable is assigned a value.
	public void setSalary(double empSal){
		salary = empSal;
	}

	// This method prints the employee details.
	public void printEmp(){
		System.out.println("name  : " + name );
		System.out.println("salary :" + salary);
	}

	public static void main(String args[]){
		Employee empOne = new Employee("Ransika");
		empOne.setSalary(1000);
		empOne.printEmp();
	}
}

Watch this video about Variables in Java in Urdu/Hindi to learn more:

 

About Faheem

An adaptable and responsible Software Engineer, who enjoys working with computers and the opportunity to learn new skills and work with new technologies is particularly attractive to me.

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2 comments

  1. good sitee for success in programming.thnx bro

  2. good sitee for success in programming.thnx bro

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