9.10. Mixed Up Code Practice

Try to solve each of the following. Click the Check button to check each solution. You will be told if your solution is too short, has a block in the wrong order, or you are using the wrong block. Some of the problems have an extra block or two that aren’t needed in the correct solution. Try to solve these on your phone or other mobile device!

The following program segment should create an empty Dog class that is a child of the Animal class. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Dog extends Animal
{
---
public Animal class Dog  #distractor
{
---
public class Animal extends Dog  #distractor
{
---
public class Dog implements Animal  #distractor
{
---
} // end class
        

The following program should overload a void method talk with no parameters. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class GenericPerson
{
   public void talk()
   {
      System.out.println("Hello!");
   }
}

public class Person extends GenericPerson
{
---
   public void talk(String name)
   {
      System.out.println("Hello " + name + "!");
   }
---
   public String talk()
   {
      return "Hello!";
   } #distractor
---
   public char talk()
   {
      return 'y';
   } #distractor
---
} // end class
        

There is a Car class whose implementation is not shown with a private int instance variable numWheels set to 4 and a no-argument constructor. There should also be a Sedan class that inherits from Car while adding an integer numSeats instance variable set to 5. The Minivan class should also inherit from Car while having its own numSeats instance variable that is set to 7. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Sedan extends Car
{
   private int numSeats = 5;
---
   public Sedan()
   {
      super();
   }
---
} // end Sedan

public class Minivan extends Car
{
   private int numSeats = 7;
---
   public Minivan()
   {
      super();
   }
} // end Minivan
        

The following program should create a class Person that has firstName and lastName as String instance variables & also has a constructor that takes those in that order. Next, the program should create a Customer class that inherits from Person (initializing the instance variables too) and also has a String instance variable called id. All three of these should be addressed in the Customer constructor. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Person
{
---
   private String firstName;
   private String lastName;
---
   public Person(String firstName, String lastName)
   {
      this.firstName = firstName;
      this.lastName = lastName;
   }

} // end Person class
---
public class Customer extends Person
{
   private String id;
---
   public Customer(String firstName, String lastName, String id)
   {
---
      super(firstName, lastName);
      this.id = id;
---
      this.firstName = firstName;
      this.lastName = lastName;
      this.id = id; #paired
---
   } // end Customer constructor
} // end Customer class
        

There should be a House class with private int instance variables numWindows and numDoors and a constructor that takes those in that order. There should also be a MobileHouse class that inherits from House while adding a numWheels instance variable (and thus has a constructor that takes numWindows, numDoors, and numWheels in that order). But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class House
{
---
   private int numWindows;
   private int numDoors;
---
   public House(int numWindows, int numDoors)
   {
---
      this.numWindows = numWindows;
      this.numDoors = numDoors;
---
   }
} // end house

public class MobileHouse extends House
{
---
   private int numWheels;
---
   public MobileHouse(int numWindows, int numDoors, int numWheels)
   {
---
      super(numWindows, numDoors);
      this.numWheels = numWheels;
---
   }
} // end MobileHouse
        

The following program should create a class Entity that has healthPoints as an integer instance variable, a constructor that takes that as an argument, and a fight() method that prints "Attacked the hero!" and returns nothing. Next, the program should create a Hero class that inherits from Entity and has a zero-argument constructor that initializes healthPoints to 100. Finally, the Hero class should override the fight() method, instead printing "Attacked the enemy!". But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Entity
{
   private int healthPoints;

   public Entity(int HP)
   {
      this.healthPoints = HP;
   }
---
   public void fight()
   {
      System.out.println("Attacked the hero!");
   }
---
} // end Entity

public class Hero extends Entity
{
---
   public Hero()
   {
      super(100);
   }
---
   public void fight()
   {
      System.out.println("Attacked the enemy!");
   }
---
   public void fight()
   {
      super.fight("Attacked the enemy!");
   } #paired
---
} // end Hero
        

The following program should create a Furniture class. The class should have a String instance variable material and a integer instance variable cost. The Furniture class should also include an equals() method that returns true if two Furniture objects have the same material and cost. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Furniture
{
---
   private String material;
   private int cost;
---
   public boolean equals(Furniture other)
   {
---
      return material.equals(other.material) && cost == other.cost;
---
   } // end equals
} // end class
        

There is a Car class whose implementation is not shown. The Car class has a method called drive() that prints "vroom". The following program should create a subclass of Car called Racecar. The Racecar class should override drive() with a new drive() function that prints "vroom" twice by calling Car’s drive() function twice. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Racecar extends Car
{

// other methods and instance variables not shown
---
public class Racecar
{ #paired

// other methods and instance variables not shown
---
   public void drive()
   {
---
      super.drive();
      super.drive();
---
      this.drive();
      this.drive(); #paired
---
   } // end drive
} // end class
        

There is a Computer class with private String instance variables name and company. You should override the Object equals method to evaluate whether both Computers have the same name and company, in which case they are “equal”. There is also a Laptop class that inherits from Computer while adding a String keyboardType instance variable. The Laptop class should override the equals method from Computer, instead evaluating whether the name, company, and keyboardType are the same (remember that name and company are not readable to Laptop so some polymorphism might be needed). But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Computer
{
   // methods and variables not shown
---
   public boolean equals(Computer other)
   {
      return name.equals(other.name) && company.equals(other.company);
   } // end equals
---
} // end Computer

public class Laptop extends Computer
{
   // methods and variables not shown
---
   public boolean equals(Laptop other)
   {
---
      return super.equals(other) && keyboardType.equals(other.keyboardType);
---
      return name.equals(other.name) && company.equals(other.company) && keyboardType.equals(other.keyboardType); #paired
---
   } // end equals
} // end Laptop
        

There is a Food class (whose implementation is not shown) with a private numCalories integer instance variable. Food has a chomp() method that returns nothing and prints "{numCalories} calories consumed" (e.g., "5 calories consumed"). There should also be a Fruit subclass that inherits from Food and adds the private color String instance variable. The Fruit class should override the Food chomp() method to return nothing, print "{numCalories} calories consumed", and print "fruit is {color}" (on a new line). Finally, there should be an Apple subclass that inherits from Fruit, sets color to "red", and adds a variety String private instance variable. The Apple class should have an overriden chomp() method that returns nothing, prints "{numCalories} calories consumed", prints "fruit is {color}", and prints "ate {variety} apple" (all separated by new lines). Remember that the numCalories and color variables are private, so the Apple class does NOT have access to their values. But, the blocks have been mixed up and may include extra blocks that are not needed in a correct solution. Drag the needed blocks from the left and put them in the correct order on the right. Click the Check button to check your solution.

        public class Fruit extends Food
{
   // instance variables and methods not shown
---
   public void chomp()
   {
---
      super.chomp();
---
      System.out.println("fruit is " + color);
---
   }
} // end Fruit
---
public class Apple extends Fruit
{
   // instance variables and methods not shown
---
   public void chomp()
   {
---
      super.chomp();
---
      System.out.println("ate " + variety + " apple");
   }
} // end Apple
        

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