Need to eliminate the redundant objects in a array list

Question

Menu Driven java program to take input and display details of the employee. When the user wants to add an employee he chooses option 1 whereas he chooses option 5 to display the details he entered.

I tried the list.contains(Object o) method but it keeps adding the repeated object into the list. Right now I have removed that part of the code.

class Employee {

    Scanner sc = new Scanner(System.in);

    int empid, num;

    String empname, empdesignation, empdept, empproject;
    //static ArrayList al = new ArrayList();


    public void setEmpNo(int n) {
        this.num = n;
    }

    public int getEmpNo() {
        return num;
    }

    public int getID() {
        return empid;
    }

    public void setID(int id) {
        this.empid = id;
    }

    public String getName() {
        return empname;
    }

    public void setName(String name) {
        this.empname = name;
    }

    public String getDept() {
        return empdept;
    }

    public void setDept(String dept) {
        this.empdept = dept;
    }

    public String getDesig() {
        return empdesignation;
    }

    public void setDesig(String desig) {
        this.empdesignation = desig;
    }

    public String getProject() {
        return empproject;
    }

    public void setProject(String proj) {
        this.empproject = proj;
    }

    public void displayemp(int id, String name, String dept, String designation, String project) {
        System.out.print("\n============================================================\n");
        System.out.println("ID: " + id);
        System.out.println("Name: " + name);
        System.out.println("Department: " + dept);
        System.out.println("Designation: " + designation);
        System.out.println("Project: " + project);
        System.out.print("\n============================================================\n");

    }


}

public class trying {

    public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);

        int ch = 0, id, n, empID, pid, projectID;
        // final int maxEmp=1000;

        String name, designation, dept, pname, mgrname, project;

        Employee emp10 = new Employee();
        Project proj10 = new Project();
        List<Employee> list = new ArrayList<Employee>();
        List<Project> list1 = new ArrayList<Project>();
        // String[] p2=new String[100];
        do {

            System.out.println("MENU");

            System.out.println(
                    " 1.Add Employee\n 2.Add Project \n 3.Edit Employee\n 4.Edit Project\n 5.Show Employee Deatils \n 6.Show Project Details \n 7.Exit");

            // System.out.println("Enter the maximum number of employees: ");

            // Employee[] emp=new Employee[maxEmp];

            System.out.print("Enter choice: ");
            try {

                ch = sc.nextInt();

                sc.nextLine();

            } catch (Exception e) {
                System.out.println("Enter an Integer value");
            }
            switch (ch) {

            case 1:
                // Employee emp6 = new Employee(1,"qwe","asd","zxc","qazwsxedc");
                // Employee emp7 = new Employee(2,"q","d","z","q");
                System.out.println("Enter the number of employees to be entered: ");
                try {
                    n = sc.nextInt();
                    emp10.setEmpNo(n);
                    if (n < 0) {
                        System.out.println("Only Positive Numbers & no Letters Please!");
                        continue;
                    }

                    for (int i = 0; i < n; i++) {
                        Employee emp5 = new Employee();

                        System.out.print("\n============================================================\n");

                        System.out.print("Enter ID: ");



                            id = sc.nextInt();
                            try {
                                if (id < 0) {
                                System.out.println("Enter an Integer value");
                                continue;
                            }

                            emp5.setID(id);

                        } catch (InputMismatchException e) {
                            System.out.println("Enter an Integer value");
                            sc.next();
                            System.exit(0);
                        }

                        sc.nextLine();
                        System.out.print("Enter Name: ");

                        name = sc.nextLine();

                        emp5.setName(name);

                        System.out.print("Enter Department: ");

                        dept = sc.nextLine();

                        emp5.setDept(dept);

                        System.out.print("Enter Designation: ");

                        designation = sc.nextLine();

                        emp5.setDesig(designation);

                        System.out.print("Enter Project: ");

                        project = sc.nextLine();

                        emp5.setProject(project);

                        System.out.print("\n============================================================\n");
                        // emp5.displayemp(id, name, dept, designation, project);

                        list.add(emp5);
                        // list.add(emp7);

                    }
                }

                catch (InputMismatchException e) {
                    System.out.println("Enter an Integer value");
                    sc.next(); // this consumes the invalid token
                }

case 5:
                System.out.println("Showing Employee Details:");
                for (Employee e : list) {
                    System.out.print("\n============================================================\n");
                    System.out.println("Id: " + e.empid + "\nName: " + e.empname + "\nDept: " + e.empdept + "\nDesig: "
                            + e.empdesignation + "\nProject: " + e.empproject);
                    System.out.print("\n============================================================\n");

                }
                break;

I want this code to remove the same entries made by the user ie., no redundant entries.

Current output

Id: 1 Name: q Dept: a Desig: z Project: qaz

============================================================

Id: 1 Name: q Dept: a Desig: z Project: qaz

============================================================

Expected output

Id: 1 Name: q Dept: a Desig: z Project: qaz

============================================================

if the list should only contain unique items can you use a `Set`? — Quince, Jul 10 '19 at 04:33
Implement hashCode() in Employees class and save it in HashSet — Abhinn Ankit, Jul 10 '19 at 04:35
Always search Stack Overflow thoroughly before posting. Study existing code samples, comparing to your own code. — Basil Bourque, Jul 10 '19 at 04:48
yes any kind of collection class can be used. how to do it using hashset? — Vedanth Vinay, Jul 10 '19 at 04:49
And read about clean code. Your code is so deeply nested that most people won't feel motivated to even look at it. A method should do 1 thin, not 20. Also note that class names go UpperCase in Java! — GhostCat, Jul 10 '19 at 05:09

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

list.contains(Object o) needs a bit of extra help before it's willing to find objects in itself. According to this post, ArrayList implements the List interface, which uses equals() to compare two objects; when using contains(), you must have an equals() method defined in your class.

Perhaps something like this:

class Employee {
 //...
  @Override
  public boolean equals(Object o) {
    boolean same = true;
    
    if(o != null && o instanceof Employee) {
      //check all member variables - remember to use .equals() for string comparison 
      if(
        (this.empId != o.empId) ||
        (this.num != o.num) ||
        (!(this.empname.equals(o.empname)) ||
        (!(this.emdesignation.equals(o.empdesignation)) ||
        (!(this.empdept.equals(o.empdept)) ||
        (!(this.empproject.equals(o.empproject))
      ) {
        same = false;
      }
    }
    else {
      //can't be equal if it's null or not an employee
      same = false;
    }

    return same;
  }
}

Once your equals function is defined, you can check if an employee is already in your ArrayList by using list.contains(emp5).

Need to eliminate the redundant objects in a array list

Current output

Expected output

1 Answers1