Question

Complete the implementation of the Die class. Note that the Die class uses an array to represent the faces of a die.

You need to complete the no-argument constructor and the two methods compareTo and equals.

Code:

import java.util.Arrays;
import java.util.Objects;
import java.util.Random;

/*
* NOTE TO STUDENTS:
* The constructor that you need to complete can be found on line 47.
*
* The two methods you need to complete can be found at the end of this file.
*/

public class Die implements Comparable<Die> {

   /**
   * A random number generator to simulate rolling the die.
   * DO NOT CHANGE THE DECLARATION OF rng. THE UNIT TESTS RELY
   * ON BEGIN ABLE TO ACCESS THE RANDOM NUMBER GENERATOR.
   */
   Random rng = new Random();
  
   /**
   * The array of face values.
   */
   private int[] faces;
      
   /**
   * The current value of the die.
   */
   private int value;
  
   /**
   * The number of faces on a die.
   */
   public static int NUMBER_OF_FACES = 6;
  

   /*
   * You need to implement the no-argument constructor below, and the
   * methods compareTo and equals found at the end of the class.
   */
  
   public Die() {
      
   }
  

   private static boolean isInAscendingOrder(int[] a) {
       for (int i = 1; i < a.length; i++) {
           if (a[i] < a[i - 1]) {
               return false;
           }
       }
       return true;
   }
  

   public Die(int[] faces) {
       if (faces.length != 6) {
           throw new IllegalArgumentException();
       }
       if (!Die.isInAscendingOrder(faces)) {
           throw new IllegalArgumentException();
       }
       this.faces = Arrays.copyOf(faces, NUMBER_OF_FACES);
       this.value = this.faces[0];
   }
  

   public void setValueToFace(int face) {
       if (face < 0 || face >= NUMBER_OF_FACES) {
           throw new IllegalArgumentException();
       }
       this.value = this.faces[face];
   }
  

   public int value() {
       return this.value;
   }
  

   public int roll() {
       int idx = rng.nextInt(Die.NUMBER_OF_FACES);
       this.value = this.faces[idx];
       return this.value;
   }

  
   @Override
   public int hashCode() {
       return Objects.hash(this.value, this.faces);
   }

  
   /*
   * You need to implement the compareTo and equals methods below.
   *
   */
  
   @Override
   public int compareTo(Die other) {
      
   }
  

   @Override
   public boolean equals(Object obj) {
       // The method Arrays.equals may be useful for helping
       // to implement this method.
      
   }
  

}

Answer 1

Constructor implementation:

public Die() {
this.faces = new int[]{1,2,3,4,5,6};
this.value = this.faces[0];
}
  

Implementation of method compareTo(Die other):

@Override
public int compareTo(Die other) {

if(this.value == other.value)
return this.value;
else return 0;
}
  

Implementation of method equals(Object obj):

@Override
public boolean equals(Object obj) {
// The method Arrays.equals may be useful for helping
// to implement this method.
  
if(obj != null && obj.getClass()== this.getClass())
return true;
return false;
  
}

Complete Code:

import java.util.Arrays;
import java.util.Objects;
import java.util.Random;

/*
* NOTE TO STUDENTS:
* The constructor that you need to complete can be found on line 47.
*
* The two methods you need to complete can be found at the end of this file.
*/

public class Die implements Comparable<Die> {

/**
* A random number generator to simulate rolling the die.
* DO NOT CHANGE THE DECLARATION OF rng. THE UNIT TESTS RELY
* ON BEGIN ABLE TO ACCESS THE RANDOM NUMBER GENERATOR.
*/
Random rng = new Random();
  
/**
* The array of face values.
*/
private int[] faces;
  
/**
* The current value of the die.
*/
private int value;
  
/**
* The number of faces on a die.
*/
public static int NUMBER_OF_FACES = 6;
  

/*
* You need to implement the no-argument constructor below, and the
* methods compareTo and equals found at the end of the class.
*/
  
public Die() {
this.faces = new int[]{1,2,3,4,5,6};
this.value = this.faces[0];
}
  

private static boolean isInAscendingOrder(int[] a) {
for (int i = 1; i < a.length; i++) {
if (a[i] < a[i - 1]) {
return false;
}
}
return true;
}
  

public Die(int[] faces) {
if (faces.length != 6) {
throw new IllegalArgumentException();
}
if (!Die.isInAscendingOrder(faces)) {
throw new IllegalArgumentException();
}
this.faces = Arrays.copyOf(faces, NUMBER_OF_FACES);
this.value = this.faces[0];
}
  

public void setValueToFace(int face) {
if (face < 0 || face >= NUMBER_OF_FACES) {
throw new IllegalArgumentException();
}
this.value = this.faces[face];
}
  

public int value() {
return this.value;
}
  

public int roll() {
int idx = rng.nextInt(Die.NUMBER_OF_FACES);
this.value = this.faces[idx];
return this.value;
}

  
@Override
public int hashCode() {
return Objects.hash(this.value, this.faces);
}

  
/*
* You need to implement the compareTo and equals methods below.
*
*/
  
@Override
public int compareTo(Die other) {

if(this.value == other.value)
return this.value;
else return 0;
}
  

@Override
public boolean equals(Object obj) {
// The method Arrays.equals may be useful for helping
// to implement this method.
  
if(obj != null && obj.getClass()== this.getClass())
return true;
return false;
  
}
  

}