1) I have two classes Employee and Department as shown below.

class Employee {
	int id; 
	String name;
	Department dept; 
	double salary; 
   //setter/getter methods 
   //override equals method 
   //override toString
   //override hasCode
   } 
class Department { 
	int deptId; 
	String deptName; 
	String location; 
	//setter/getter methods
	//override equals method
	//override equals method 
	//override toString 
}

–> for me, two employee objects are same when empId, empName and his Department are same. So, write a program to accept number of employee and employee details through console and filter the duplicate employees and display the result.

Solution

package com.bellinfo.batch3.corejava.day8;

import java.util.Scanner;

public class EmployeeDemoExample1 {
	Scanner scan;

	public static void main(String[] args) {
		EmployeeDemoExample1 ede =new EmployeeDemoExample1();
		StudentDetails[] uniqueSDArray = ede.recieveInputsFromConsole();
		ede.displayResults(uniqueSDArray);
	}

	/**
	 * method to receive inputs from console
	 * @return
	 */
	StudentDetails[] recieveInputsFromConsole(){
		scan = new Scanner(System.in);
		System.out.println("enter student count:");
		int studentCount = scan.nextInt();
		StudentDetails[] originalStudArray = new StudentDetails[studentCount];
		StudentDetails[] uniqueStudArray = new StudentDetails[studentCount];
		System.out.println("");
		for(int i=0;i<=studentCount-1;i++){
			System.out.println("Student Details"+i+" :");
			System.out.println("Student Id:");
			int sId =scan.nextInt();
			System.out.println("Student Name:");
			String sName = scan.next();
			System.out.println("Course Id:");
			int cId = scan.nextInt();
			System.out.println("Course Name:");
			String cName = scan.next();
			System.out.println("Course Duration:");
			int cDuration = scan.nextInt();
			
			StudentDetails sd =populateStudentDetails(sId, sName, cId, cName, cDuration);
			originalStudArray[i] =sd;
		}
		uniqueStudArray = eliminateDuplicateStudentRecords(originalStudArray);
		return uniqueStudArray;
	}
	
	/***
	 * Method used to process inputs and populate the object required.
	 * @param sId
	 * @param sName
	 * @param cId
	 * @param cName
	 * @param cDuration
	 * @return
	 */
	StudentDetails populateStudentDetails(int sId, String sName, int cId, String cName, int cDuration){
		Course c = new Course();
		c.setCourseId(cId);
		c.setCourseName(cName);
		c.setCourseDuration(cDuration);
		
		StudentDetails sd = new StudentDetails();
		sd.setStudentId(sId);
		sd.setStudentName(sName);
		sd.setCourse(c);
		
		return sd;
		
	}
	
	/**
	 * Logic to eliminate the duplicates
	 * @param orignialStudArray
	 * @return
	 */
	StudentDetails[] eliminateDuplicateStudentRecords(StudentDetails[] orignialStudArray){
		StudentDetails[] filteredArray = new StudentDetails[orignialStudArray.length];
		filteredArray = orignialStudArray.clone();
		for(int i=0; i<=orignialStudArray.length-1; i++){
			StudentDetails sd1 = orignialStudArray[i];
			for(int j=i+1,y=0;j<=orignialStudArray.length-1;j++){
				StudentDetails sd2 = orignialStudArray[j];
				if(sd1.equals(sd2)){
					filteredArray[j] =null;
				}
			 }
		}
		
		
		return filteredArray;
		
	}
	
	/**
	 * This method used for displaying the results after filtering the results.
	 * @param array
	 */
	void displayResults(StudentDetails[] array){
		System.out.println("****************************************");
		System.out.println("********Unique Student Records**********");
		System.out.println("****************************************");
		System.out.println("Id"+"     "+"Name"+"     "+"CId"+"     "+"CName"+"     "+"CDuration");
		for(int i=0;i<=array.length-1;i++){
			if(array[i]!=null){
				StudentDetails sd = array[i];
				System.out.println(sd.toString());
			}
		}
	}
}



class StudentDetails  {
	private int studentId;
	private String studentName;
	private Course course;
	
	
	
	public int getStudentId() {
		return studentId;
	}

	public void setStudentId(int studentId) {
		this.studentId = studentId;
	}

	public String getStudentName() {
		return studentName;
	}

	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}

	public Course getCourse() {
		return course;
	}

	public void setCourse(Course course) {
		this.course = course;
	}

	public boolean equals(Object otherStudent){
		if(otherStudent ==null){
			return false;
		}
		if(otherStudent instanceof StudentDetails){
		   StudentDetails sdOtherObject = (StudentDetails)otherStudent;
		   if(this.studentId ==sdOtherObject.studentId && this.studentName.equals(sdOtherObject.studentName)
			   && this.course.equals(sdOtherObject.course)){
			   return true;
		   }
			
		}
		return false;
		
	}
	
	public int hashCode(){
		return 31*studentId*studentName.hashCode()*course.hashCode();
		
	}
	public String toString(){
		return studentId+"     "+studentName+"     "+ course;
	}
	
}
class Course{
	private int courseId;
	private String courseName;
	private int courseDuration;
	
	public int getCourseId() {
		return courseId;
	}
	public void setCourseId(int courseId) {
		this.courseId = courseId;
	}
	public String getCourseName() {
		return courseName;
	}
	public void setCourseName(String courseName) {
		this.courseName = courseName;
	}
	public int getCourseDuration() {
		return courseDuration;
	}
	public void setCourseDuration(int courseDuration) {
		this.courseDuration = courseDuration;
	}
	
	public boolean equals(Object otherCourse){
		 if(otherCourse ==null){
			 return false;
		 }
		 if(otherCourse instanceof Course){
			 Course otherObj = (Course) otherCourse;
			 if(this.courseId==otherObj.courseId && this.courseName.equals(otherObj.courseName)
					 && this.courseDuration==this.getCourseDuration()){
				 return true;
				 
			 }
		 }
		 return false;
	}
	
	public int hashCode(){
		return 31*courseId*courseDuration*courseName.hashCode();
		
	}
	public String toString(){
		return courseId+"     "+courseName+"     "+courseDuration;
	}
	
	
}

ouput / console:

****************************************
********Unique Student Records**********
****************************************
Id     Name     CId     CName     CDuration
1     Siva     121     Java     3
2     Teju     121     .net     3