JAVA TUTORIALS - Java - Object & Classes
Java - Object & Classes
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Classes in Java:
public class Dog{ String breed; int age; String color; void barking(){ } void hungry(){ } void sleeping(){ } }ADVERTISEMENTSConstructors:
public class Puppy{ public puppy(){ } public puppy(String name){ // This constructor has one parameter, name. } }ADVERTISEMENTSCreating an Object:
public class Puppy{ public Puppy(String name){ // This constructor has one parameter, name. System.out.println("Passed Name is :" + name ); } public static void main(String []args){ // Following statement would create an object myPuppy Puppy myPuppy = new Puppy( "tommy" ); } }
Passed Name is :tommyAccessing Instance Variables and Methods:
/* First create an object */ ObjectReference = new Constructor(); /* Now call a variable as follows */ ObjectReference.variableName; /* Now you can call a class method as follows */ ObjectReference.MethodName();Example:
public class Puppy{ int puppyAge; public Puppy(String name){ // This constructor has one parameter, name. System.out.println("Passed Name is :" + name ); } public void setAge( int age ){ puppyAge = age; } public int getAge( ){ System.out.println("Puppy's age is :" + puppyAge ); return puppyAge; } public static void main(String []args){ /* Object creation */ Puppy myPuppy = new Puppy( "tommy" ); /* Call class method to set puppy's age */ myPuppy.setAge( 2 ); /* Call another class method to get puppy's age */ myPuppy.getAge( ); /* You can access instance variable as follows as well */ System.out.println("Variable Value :" + myPuppy.puppyAge ); } }
Passed Name is :tommy Puppy's age is :2 Variable Value :2Import statements:
import java.io.*;A Simple Case Study:
import java.io.*; public class Employee{ String name; int age; String designation; double salary; // This is the constructor of the class Employee public Employee(String name){ this.name = name; } // Assign the age of the Employee to the variable age. public void empAge(int empAge){ age = empAge; } /* Assign the designation to the variable designation.*/ public void empDesignation(String empDesig){ designation = empDesig; } /* Assign the salary to the variable salary.*/ public void empSalary(double empSalary){ salary = empSalary; } /* Print the Employee details */ public void printEmployee(){ System.out.println("Name:"+ name ); System.out.println("Age:" + age ); System.out.println("Designation:" + designation ); System.out.println("Salary:" + salary); } }
import java.io.*; public class EmployeeTest{ public static void main(String args[]){ /* Create two objects using constructor */ Employee empOne = new Employee("James Smith"); Employee empTwo = new Employee("Mary Anne"); // Invoking methods for each object created empOne.empAge(26); empOne.empDesignation("Senior Software Engineer"); empOne.empSalary(1000); empOne.printEmployee(); empTwo.empAge(21); empTwo.empDesignation("Software Engineer"); empTwo.empSalary(500); empTwo.printEmployee(); } }
C :> javac Employee.java C :> vi EmployeeTest.java C :> javac EmployeeTest.java C :> java EmployeeTest Name:James Smith Age:26 Designation:Senior Software Engineer Salary:1000.0 Name:Mary Anne Age:21 Designation:Software Engineer Salary:500.0