How do I use compareTo

Question

Please help. I'm new to this and I can't figure out how to use compareTo. I need to try to get the output looking like this:
name1 bill1 bill2
name2 bill1 bill2
name3 bill1 bill2
etc.
It currently does this:
name1 bill1
name2 bill1
name1 bill2
etc.
How do I do this????
public class BillingList
private static final int MAXIMUM_NUMBER_OF_BILLS = 100;
private Bill[] bills;
private int numberOfBills;
public BillingList()
bills = new Bill[MAXIMUM_NUMBER_OF_BILLS];
numberOfBills = 0;
public void addBill(String customerName, double amountOwedByCustomer)
bills[numberOfBills] = new Bill(customerName, amountOwedByCustomer);
++numberOfBills;
public void payBill(String customerName, double amountPaid)
if(numberOfBills > 1)
     { for(int i = 0; i < numberOfBills; ++i)
          {if(bills[i].getAmount() >= amountPaid)
                    {double amountChanged = bills[i].getAmount() - amountPaid;
                         bills.setAmount(amountChanged);
public double totalOwed(String customerName)
double total = 0.00;
for (int i = 0; i < numberOfBills; ++i)
total += bills[i].getAmount();
return total;
public String toString()
String result = "";
for (int i = 0; i < numberOfBills; i++)
result += bills[i].getName() + ": " + bills[i].getAmount() +"\n";
return result;
public static void main(String[] args)
BillingList accounts = new BillingList();
accounts.addBill("Joe", 123.45);
accounts.addBill("Mary", 321.11);
accounts.addBill("Charlie", 420.15);
accounts.addBill("Laura", 124.31);
accounts.addBill("Joe", 23.55);
accounts.addBill("Mary", 122.21);
accounts.addBill("Charlie", 125.78);
accounts.addBill("Jack", 76.55);
accounts.addBill("Mary", 122.34);
accounts.addBill("Charlie", 322.11);
System.out.println("Charlie's total is " +
accounts.totalOwed("Charlie"));
accounts.payBill("Charlie", 120.00);
System.out.println("Charlie paid 120.00");
System.out.println("Charlie's total is now " + accounts.totalOwed("Charlie"));
System.out.println(accounts);
public class Bill implements Comparable
private String name;
private double amount;
public Bill(String nameOnBill, double amountOwed)
name = nameOnBill;
amount = amountOwed;
public int compareTo(Object other)
Bill otherBill = (Bill)other;
return name.compareTo(otherBill.name);
public String getName()
return name;
public double getAmount()
return amount;
public void setAmount(double newAmount)
amount = newAmount;
steve

Answer 1

Try this code, no compareTo.import java.util.*;
public class BillingList {
     private static final int MAXIMUM_NUMBER_OF_BILLS = 100;
     private Bill[] bills;
     private int numberOfBills;
     private Hashtable customers;
     public BillingList() {
          bills = new Bill[MAXIMUM_NUMBER_OF_BILLS];
          customers = new Hashtable();
          numberOfBills = 0;
     public void addBill(String customerName, double amountOwedByCustomer) {
          bills[numberOfBills] = new Bill(customerName, amountOwedByCustomer);
          ++numberOfBills;
          if(!customers.containsKey(customerName)) customers.put(customerName,customerName);
     public void payBill(String customerName, double amountPaid) {
          boolean found=false;
          for(int i = 0; i < numberOfBills; i++) {
               if(bills[ i ].getName().equalsIgnoreCase(customerName)) {
                    if(bills[ i ].getAmount() >= amountPaid) {
                         double amountChanged = bills[ i ].getAmount() - amountPaid;
                         bills[ i ].setAmount(amountChanged);
                         found=true;
          if(!found) System.out.println("Nothing to pay the customer "+customerName);
     public double totalOwed(String customerName) {
          double total = 0.00;
          for (int i = 0; i < numberOfBills; ++i) {
               if(bills[ i ].getName().equalsIgnoreCase(customerName))
                    total += bills[ i ].getAmount();
          return total;
     public String toString() {
          Enumeration e = customers.elements();
          String result="";
          while(e.hasMoreElements()) {
               String customer = (String)e.nextElement();
               result += customer+" : ";
               for (int i = 0; i < numberOfBills; i++) {
                    if(bills[ i ].getName().equalsIgnoreCase(customer)) {
                         result += bills[ i ].getAmount() +" ";
               result += "\n";
          return result;
     public static void main(String[] args) {
          BillingList accounts = new BillingList();
          accounts.addBill("Joe", 123.45);
          accounts.addBill("Mary", 321.11);
          accounts.addBill("Charlie", 420.15);
          accounts.addBill("Laura", 124.31);
          accounts.addBill("Joe", 23.55);
          accounts.addBill("Mary", 122.21);
          accounts.addBill("Charlie", 125.78);
          accounts.addBill("Jack", 76.55);
          accounts.addBill("Mary", 122.34);
          accounts.addBill("Charlie", 322.11);
          System.out.println("Charlie's total is " +
          accounts.totalOwed("Charlie"));
          accounts.payBill("Charlie", 120.00);
          System.out.println("Charlie paid 120.00");
          System.out.println("Charlie's total is now " + accounts.totalOwed("Charlie"));
          System.out.println(accounts);
}Sudha