Review for Quiz 2

Question 2-1

What is the purpose of a constructor method?

Question 2-2

The following program uses the Account class we defined in class.

import csbsju.cs160.*;

public class PrintHello {
    public static void main(String[] args) {
        Account a = new Account();
        a.deposit(80.0);
        Account b = a;
        b.withdraw(20.0);
        b = new Account();
        b.deposit(40.0);
        IO.println(a.getBalance());
    }
}

What does this program print?

Question 2-3

Write a program that reads a name from the user and displays the number of lower-case r's occurring in the name.

Name? Carl Bryan Burch
You have 3 r's.

You'll want to use the instance methods length() and charAt() defined in the String class. Your program's interface should be identical to the above transcript.

import csbsju.cs160.*;

public class PrintHello {
    public static void main(String[] args) {


    }
}

Question 2-4

Write a method that, given an Account, generates and returns a duplicate account holding the same amount of money. Use the Account object interface described as follow.

Constructors
`Account()`	Creates a new account holding no money.
Object methods
`double getBalance()`	Returns the amount of money held in the object account.
`void deposit(double amt)`	Adds `amt` dollars to the object account's balance.
`void withdraw(double amt)`	Subtracts `amt` dollars from the object account's balance.

public static Account duplicate(Account acct) {


}

Solutions

Solution 2-1

Its purpose is to initialize the instance variables of a newly allocated object.

Solution 2-2

60.0

Solution 2-3

public class PrintHello {
    public static void main(String[] args) {
        IO.print("Name? ");
        String name = IO.readLine();
        int count = 0;
        for(int i = 0; i < name.length(); i++) {
            if(name.charAt(i) == 'r') ++count;
        }
        IO.println("You have " + count + " r's.");
    }
}

Solution 2-4

public static Account duplicate(Account acct) {
    Account ret = new Account();
    ret.deposit(acct.getBalance());
    return ret;
}