Need help filling in the areas, unsure of how to do the code, JAVA. I've highlited what needs completing. 

 /** Sort bankaccounts using the interface Comparable and the classes ArrayList, Collections. Todo: In the BankAccount class you make BankAccount implement Comparable. The sorting here should be from small to large balances. */ import javax.swing.* ; import java.util.* ; public class BankAccountSorter { public static void main(String[] args) { ArrayList list = new ArrayList() ; list.add(new BankAccount(1000)) ; list.add(new BankAccount(500)) ; list.add(new BankAccount(30)) ; list.add(new BankAccount(600)) ; list.add(new BankAccount(20)) ; System.out.println(list) ; Collections.sort(list) ; System.out.println(list) ; } } /** A bankAccount object has a balance that can be changed by deposits and withdrawals. Here the class is modified to implement Comparable. Sorting is from small balances to large. */ //-----------Start below here. To do: approximate lines of code = 1 // Write the "class BankAccount ... " part so that Comparable is implemented //-----------------End here. Please do not remove this comment. Reminder: no changes outside the todo regions. { //instance variables private double balance; //the money in the account /** Constructs a bankAccount account with a zero balance. */ public BankAccount() { balance = 0; } /** Constructs a bank account with a given balance. @param aBalance the initial balance */ public BankAccount(double aBalance) { balance = aBalance; } /** Deposits money into the bank account. @param amount the amount to deposit */ public void deposit(double amount) { double newBalance = balance + amount; balance = newBalance; } /** Withdraws money from the bank account. @param amount the amount to withdraw */ public void withdraw(double amount) { double newBalance = balance - amount; balance = newBalance; } /** Gets the current balance of the bank account. @return the current balance */ public double getBalance() { return balance; } /** Gives a string representation of the bankaccount, but in this case the string is just the balance. @return the balance as a string */ public String toString() { return "" + balance ; } /** Compares balances in the way required by the interface @return 1 if this balance is bigger than the other balance -1 if this balance is less 0 if they are the same. */  //-----------Start below here. To do: approximate lines of code = 4 // 1. public signature ; //2. code for the -1 case ; //3. code for the 1 case ; //4. code for the 0 case.  //-----------------End here. Please do not remove this comment. Reminder: no changes outside the todo regions. }