Question

Add code to the Account class and create a new class called BalanceComparator.

import java.util.*;

public final class Account implements Comparable {

    private String firstName;

    private String lastName;

    private int accountNumber;

    private double balance;

    private boolean isNewAccount;

    public Account(

            String firstName,

            String lastName,

            int accountNumber,

            double balance,

            boolean isNewAccount

    ) {

        this.firstName = firstName;

        this.lastName = lastName;

        this.accountNumber = accountNumber;

        this.balance = balance;

        this.isNewAccount = isNewAccount;

    }

    /**

     * TO DO: override equals

     */

    @Override

    public boolean equals(Object other) {

        return false;

    }

    /**

     * TO DO: override hashCode here

     */

    @Override

    public int hashCode() {

        return 0;

    }

    /**

     * TO DO:

     * Write compareTo (natural ordering of class):

     * 1. accountNumber in ascending order

     *      If same, break ties:

     * 2. old Accounts before new accounts

     *      If same, break ties

     * 3. LastName

     *      If same, break ties

     * 4. FirstName

     *      If same, break ties

     * 5. Lower Balance before higher balance

     */

    @Override

    public int compareTo(Account other) {

        final int BEFORE = -1;

        final int EQUAL = 0;

        final int AFTER = 1;

        return EQUAL;

    }

}

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

import java.util.Comparator;

/*

* TO DO:

*This class should compare all accounts by balance only (in ascending order)

*/

Answer 1

The updated code for Account.java class is as below:

import java.util.*;

public final class Account implements Comparable<Account> {
        
    private String firstName;
    private String lastName;
    private int accountNumber;
    private double balance;
    private boolean isNewAccount;

    public Account(String firstName,String lastName, int accountNumber,double balance,boolean isNewAccount) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.accountNumber = accountNumber;
        this.balance = balance;
        this.isNewAccount = isNewAccount;
    }

    
    public String getFirstName() {
                return firstName;
        }


        public String getLastName() {
                return lastName;
        }


        public int getAccountNumber() {
                return accountNumber;
        }


        public double getBalance() {
                return balance;
        }


        public boolean isNewAccount() {
                return isNewAccount;
        }


        public void setFirstName(String firstName) {
                this.firstName = firstName;
        }


        public void setLastName(String lastName) {
                this.lastName = lastName;
        }


        public void setAccountNumber(int accountNumber) {
                this.accountNumber = accountNumber;
        }


        public void setBalance(double balance) {
                this.balance = balance;
        }


        public void setNewAccount(boolean isNewAccount) {
                this.isNewAccount = isNewAccount;
        }
        
        /**

     * TO DO: override equals

     */

    @Override

    public boolean equals(Object other) {

        return false;

    }

    /**

     * TO DO: override hashCode here

     */

    @Override

    public int hashCode() {

        return 0;

    }

    /**

     * TO DO:

     * Write compareTo (natural ordering of class):

     * 1. accountNumber in ascending order

     *      If same, break ties:

     * 2. old Accounts before new accounts

     *      If same, break ties

     * 3. LastName

     *      If same, break ties

     * 4. FirstName

     *      If same, break ties

     * 5. Lower Balance before higher balance

     */

        @Override
        public int compareTo(Account other) {            
                 return Comparator.comparingInt(Account::getAccountNumber)
                         .thenComparing(Account::isNewAccount)
                         .thenComparing(Account::getLastName)
                         .thenComparing(Account::getFirstName)
                         .thenComparingDouble(Account::getBalance)
                         .compare(this, other);          
        }
        
        
        public String toString() {
                String str;
                if(isNewAccount)
                        str = "is new account";
                else
                        str = "is not a new account";
                return accountNumber+" "+str+" with name "+firstName+" "+lastName+" with a balance of "+ balance;
        }
}

The class used to compare any 2 Account class objects as below:

import java.util.Comparator;

public class AccountComparing  implements Comparator<Account>{

        @Override
        public int compare(Account ac1, Account ac2) {
                return ac1.compareTo(ac2);
        }
}

I have tested the above functionality using another class as below:

import java.util.Arrays;

public class Testing {
        public static void main(String[] args){
                Account ac[] = new Account[4];
                ac[0] = new Account("John", "valles", 10, 70000, true);
                ac[1] = new Account("Angel", "Lopez", 11, 8000, false);
                ac[2] = new Account("Angel", "Arun", 11, 900, true);    
                ac[3] = new Account("Angel", "Arun", 11, 700, true);
                Arrays.sort(ac);
                
                for(Account a : ac){
                        System.out.println(a.toString());
                }
                
        }
}

The ouput screenshot of the above program is :

If you have any queries reagrding this answer, please reach out through the comment section.