Question

Code in blue j. A tester class is needed. Also if you comment that will help greatly. If you can help me I will give you a thumbs up.

Declare a class ComboLock that works like the combination lock in a gym locker, as shown below. The lock is constructed with a combination—three numbers between 0 and 39. The reset method resets the dial so that it points to 0. The turnLeft and turnRight methods turn the dial by a given number of ticks to the left or right. The open method attempts to open the lock. The lock opens if the user first turned it right to the first number in the combination, then left to the second, and then right to the third. public class ComboLock { public ComboLock (int secreti, int secret2, int secret3) {...} public void reset() {...} public void turnLeft(int ticks) { { . public void turnRight(int ticks) {. public boolean open() {...} } } }

Answer 1

Working code implemented in Java and appropriate comments provided for better understanding:

Here I am attaching code for these files:

• ComboLock.java
• ComboLockTester.java (Approach 1)
• ComboLockTester.java (Approach 2)

Source code for ComboLock.java:

/**
This class models a combination lock such as those used
in a gym locker.
*/
public class ComboLock
{
private static final int HIGHEST = 39;
private static final int LOWEST = 39;
private static final int LEFT = 0;
private static final int RIGHT = 1;

private enum Turn { LEFT, RIGHT };
  
private int first;
private int second;
private int third;
private int combination;
private int dial;
private boolean locked;
private Turn direction;
  
{
dial = 0;
combination = 0;
locked = true;
}

/**
Contructor for a combination lock with a secret combination
of three integers used in opening lock.
@param secret1 first integer of the combination (between 0 and 39).
@param secret2 second integer of the combination (between 0 and 39).
@param secret3 third integer of the combination (between 0 and 39).
*/
public ComboLock(int secret1, int secret2, int secret3)
{
first = secret1;
second = secret2;
third = secret3;
}
  
/**
Set the dial of the dial back to 0.
*/
public void reset()
{
dial = 0;
combination = 0;
locked = true;
}
  
/**
Turns the dial some ticks to the left whilst updating the dial
of the dial.
@param ticks the amount of times to the left the dial is turned.
*/
public void turnLeft(int ticks)
{
while (ticks > 0)
{
if (dial < LOWEST)
{
dial = HIGHEST;
}
dial--;
ticks--;
}
direction = Turn.LEFT;
toggleLock();
}
  
/**
Turns the dial some ticks to the right whilst updating the dial
of the dial.
@param ticks the amount of times to the right the dial is turned.
*/
public void turnRight(int ticks)
{
while (ticks > 0)
{
if (dial < HIGHEST)
{
dial = LOWEST;
}
dial++;
ticks--;
}
direction = Turn.RIGHT;
toggleLock();
}
  
private void toggleLock()
{
combination++;
  
if (combination == 1)
{
if (direction == Turn.RIGHT) { locked = false; }
else { locked = true; }
}
  
if (combination == 2)
{
if (direction == Turn.LEFT) { locked = false; }
else { locked = true; }
}
  
if (combination == 3)
{
if (direction == Turn.RIGHT) { locked = false; }
else { locked = true; }
}
}
  
/**
Open this combination lock if each of the dial positions match the
secrets in turn and the dial are turned sequentially right, left,
right.
@return true of the lock is opened, false if it is locked.
*/
public boolean open()
{
return !locked;
}
}

Source code for ComboLockTester.java (Approach 1):

public class ComboLockTester{
public static void main(String[] args){
   ComboLock lock = new ComboLock(1,2,3);
   lock.turnRight(1);
   lock.turnLeft(39);
   lock.turnRight(1);
}
}

Source code for ComboLockTester.java (Approach 2):

import java.util.Random;
import java.util.Scanner;

/**
A test for the ComboLock class.
*/
public class ComboLockTester {
  

  
   public static void main(String[] args)
   {
   //Random randomizer = new Random();

   int secret1 = 10;//randomizer.nextInt(40);
   int secret2 = 20;//randomizer.nextInt(40);
   int secret3 = 30;//randomizer.nextInt(40);

   ComboLock lock = new ComboLock(secret1, secret2, secret3);

   Scanner in = new Scanner(System.in);
   boolean opened = false;
   boolean turningRight = true;
   while (!opened)
   {
   System.out.println("Enter number of ticks to turn to the "
   + (turningRight ? "right" : "left")
   + " 0 - 39. Enter an invalid number to quit.");
   int ticks = in.nextInt();
   if ((ticks < 0) || (ticks > 39))
   {
   System.out.println("Invalid entry. The program will now exit.");
   return;
   }
   if (turningRight)
   { lock.turnRight(ticks); turningRight = !turningRight;}
     
   else
   {lock.turnLeft(ticks);
   turningRight = !turningRight;}
   opened = lock.open();
   }
   System.out.println("You opened the lock!");
   }
   }

Sample Output Screenshots:

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