Question

In Java:

Executable Class

• create an array of Employee objects. You can copy the array you made for Chapter 20.
• create an ArrayList of Employee objects from that array.
• use an enhanced for loop to print all employees as shown in the sample output.
• create a TreeMap that uses Strings for keys and Employees as values.
• this TreeMap should map Employee ID numbers to their associated Employees.
• process the ArrayList to add elements to this map.
• print all employees in ID # order as shown, but do so using the TreeMap's forEach method and a lambda expression

So far I have created the array of the 8 employee objects and the ArrayList. I have also created the enhanced for loop. I just can't figure out how to get the TreeMap to work with the ArrayList to add the elements to the map and print out the list of employees with their associated id numbers from smallest id number to largest id number.

Here is my code so far.

import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Locale;
import java.util.Map;
import java.util.TreeMap;

class Employee {
   private String id;

   private String lastName;

   private String firstName;

   private int salary;

public Employee(String _id, String ln, String fn, int sal){

   id = _id;

   firstName = fn;

   lastName = ln;

   salary = sal;

   }
   //get the id and return the id
   public String getId() {

   return id;

   }
   //get the first name and return the first name
   public String getFirstName() {

   return firstName;

   }
   //get the last name and return the last name
public String getLastName() {

   return lastName;

   }
//get the salary and return the salary
   public int getSalary() {

   return salary;

   }
   //display the employees attributes
   public String toString(){
   //format the salary
   NumberFormat formatter = NumberFormat.getInstance(Locale.US);

   return "ID "+id+":"+lastName+", "+firstName+", salary $"+formatter.format(salary);

   }

public static void main(String[] args) {
  
   //array of 8 employee objects
   Employee []employees = new Employee[8];

   employees[0] = new Employee("12345", "Baker", "Tom", 200000);

   employees[1] = new Employee("56789", "Jones", "Dan", 130000);                                              

   employees[2] = new Employee("24680", "Scott", "Ann", 90000);

   employees[3] = new Employee("13579", "Jones", "Pat", 80000);

   employees[4] = new Employee("11111", "Scott", "Bob", 65000);

   employees[5] = new Employee("23232", "Baker", "Amy", 100000);

   employees[6] = new Employee("45454", "Perez", "Ava", 105000);

   employees[7] = new Employee("67765", "Jones", "Don", 140000);
   //array list
   ArrayList<Employee> empList = new ArrayList<Employee>(Arrays.asList(employees));
   //enhanced for loop to display the employees
   System.out.println("All Employees\n");
  
   empList.forEach((e)->System.out.println(e));
}
}

Answer 1

import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Locale;
import java.util.TreeMap;

class Employee {
   private String id;

   private String lastName;

   private String firstName;

   private int salary;

   public Employee(String _id, String ln, String fn, int sal) {

       id = _id;

       firstName = fn;

       lastName = ln;

       salary = sal;

   }

   // get the id and return the id
   public String getId() {

       return id;

   }

   // get the first name and return the first name
   public String getFirstName() {

       return firstName;

   }

   // get the last name and return the last name
   public String getLastName() {

       return lastName;

   }

   // get the salary and return the salary
   public int getSalary() {

       return salary;

   }

   // display the employees attributes
   public String toString() {
       // format the salary
       NumberFormat formatter = NumberFormat.getInstance(Locale.US);

       return "ID " + id + ":" + lastName + ", " + firstName + ", salary $" + formatter.format(salary);

   }

   public static void main(String[] args) {

       // array of 8 employee objects
       Employee[] employees = new Employee[8];

       employees[0] = new Employee("12345", "Baker", "Tom", 200000);

       employees[1] = new Employee("56789", "Jones", "Dan", 130000);

       employees[2] = new Employee("24680", "Scott", "Ann", 90000);

       employees[3] = new Employee("13579", "Jones", "Pat", 80000);

       employees[4] = new Employee("11111", "Scott", "Bob", 65000);

       employees[5] = new Employee("23232", "Baker", "Amy", 100000);

       employees[6] = new Employee("45454", "Perez", "Ava", 105000);

       employees[7] = new Employee("67765", "Jones", "Don", 140000);
       // array list
       ArrayList<Employee> empList = new ArrayList<Employee>(Arrays.asList(employees));

       // displaying the employees using enhanced for loop
       for (Employee e : empList)
           System.out.println(e);
       // creating Tree Map
       TreeMap<String, Employee> map = new TreeMap<String, Employee>();
       // adding objects to TreeMap
       for (Employee e : empList)
           map.put(e.getId(), e);

       // enhanced for loop to display the employees
       System.out.println("All Employees\n");
       // using lamda expressions to display map
       map.forEach((k, v) -> System.out.println((k + ":" + v)));

   }
}