Question

java questions:

1. Explain the difference between a deep and a shallow copy.

2. Given the below classes:

public class Date {

   private String month;

   private String day;

   private String year;

   public Date(String month, String day, String year) {

      this.month = month;

      this.day = day;

      this.year = year;

   }

   public String getMonth() {

      return month;

   }

   public String getDay() {

      return day;

   }

   public String getYear() {

      return year;

   }

  

   @Override public String toString() {

      return month + "/" + day + "/" + year;

   }

}

public class Dog {

    private String name;

    private double weight;

    private Date birthday;

    public Dog(String name, double weight, Date birthday) {

        this.name = name;

        this.weight = weight;

      this.birthday = birthday;

    }

    public String getName() {

        return name;

    }

    public double getWeight() {

        return weight;

    }

    public Date getBirthday() {

        return birthday;

    }

    public void printGreeting() {

        System.out.println("Woof!");

    }

    @Override public String toString() {

        return "Name: " + name

            + "\nWeight: " + weight

            + "\nDate: " + birthday.toString();

    }

}

• Write a copy constructor for the above Dog class that creates a deep copy.

3. There is a problem with the below mutator method. Correct the problem in two different ways:

public void setAge(int age) {

    age = age;

}

4. Write a complete class named Car. It has three private member variables make (String), model (String) and mileage (double). It has 3 constructors - a default constructor, a 3-argument constructor and a copy constructor. It has accessor and mutator methods for all variables. It has a toString() method.

Answer 1

Ans 1:

In shallow copy, only fields of primitive data type are copied while the objects references are not copied. Deep copy involves the copy of primitive data type as well as objet references

Ans 2:

public Dog(String name, double weight, Date birthday) {

        this.name = new String(name);

        this.weight = weight;

        this.birthday = new Date(birthday.getTime());;

    }

Ans 3:

public void setAge(int age) {

    this.age = age;

}

Ans 4:

public class Car {
       private String make;
       private String model;
       private double mileage;
      
       //default constructor
       public Car() {
           super();
           this.make = "";
           this.model = "";
           this.mileage = 0.00;
       }
      
       //Parameterized constructor
       public Car(String make, String model, double mileage) {
           this.make = make;
           this.model = model;
           this.mileage = mileage;
       }
      
      
       //Copy Constructor
       public Car(Car c) {
           this.make = c.make;
           this.model = c.model;
           this.mileage = c.mileage;
       }
      
      
      
       public String getMake() {
           return make;
       }
       public void setMake(String make) {
           this.make = make;
       }
       public String getModel() {
           return model;
       }
       public void setModel(String model) {
           this.model = model;
       }
       public double getMileage() {
           return mileage;
       }
       public void setMileage(double mileage) {
           this.mileage = mileage;
       }
       @Override
       public String toString() {
           return "Car [make=" + make + ", model=" + model + ", mileage=" + mileage + "]";
       }
      
      
}