Java NPTEL Solutions Week 2: Mastering Advanced Java Challenges

In this blog post, we’ll dive deep into the solutions for Week 2 of your Java NPTEL course. These challenges will help you grasp more advanced concepts in Java programming. Let’s tackle each question efficiently while keeping our code clean and concise.

Java Week 2: Q1 - Calling ‘print()’ Using Inner Classes

In this problem, we have an outer class School and an inner class Student. To call the print() method in the Student class, you can create an object of the inner class and use it to invoke the print() method. Here’s the solution:

class School {
    class Student {
        public void print() {
            System.out.println("Hi! I am inner class STUDENT of outer class SCHOOL.");
        }
    }
}

public class Question211 {
    public static void main(String[] args) {
        School.Student s1 = new School().new Student();
        s1.print();
    }
}

Explanation: We create an object of the inner class Student using School.Student s1 = new School().new Student(); and then call the print() method on this object.

Java Week 2: Q2 - Calling Methods of Different Classes

In this question, we have two separate classes, School and Student, each with its own print() method. To call these methods, you can create objects of the respective classes and invoke their print() methods. Here’s the solution:

class School {
    public void print() {
        System.out.println("Hi! I am class SCHOOL.");
    }
}

class Student {
    public void print() {
        System.out.println("Hi! I am class STUDENT");
    }
}

public class Question212 {
    public static void main(String[] args) {
        Student stu = new Student();
        stu.print();

        School sch = new School();
        sch.print();
    }
}

Explanation: We create objects of both the Student and School classes and then call their respective print() methods.

Java Week 2: Q3 - Calling Methods by Creating a New Method

In this question, you need to call the print() method of class Question by creating a method named studentMethod(). Here’s the solution:

public class Question213 {
    public static void main(String[] args) {
        Question213 q = new Question213();
        q.studentMethod();
    }

    void print(Question213 object) {
        System.out.print("Well Done!");
    }

    void studentMethod() {
        Question213 q = new Question213();
        q.print(q);
    }
}

Explanation: We create an object of the Question213 class and call the studentMethod(), which in turn calls the print() method of the same class.

Java Week 2: Q4 - Calling Constructors in a Specific Order

This question involves calling constructors in a specific order in the Answer class. We create an object of the Answer class with the appropriate constructor. Here’s the solution:

public class Question214 {
    public static void main(String[] args) {
        Answer a = new Answer(10, "MCQ");
    }
}

class Answer {
    Answer() {
        System.out.println("You got nothing.");
    }

    Answer(int marks, String type) {
        this();
        System.out.println("You got " + marks + " for an " + type);
    }
}

Explanation: We create an object of the Answer class using the constructor with parameters, which in turn calls the default constructor using this().

Java Week 2: Q5 - Debugging to Print ‘NPTEL JAVA’

This question requires debugging to print the text ‘NPTEL JAVA.’ Here’s the corrected solution:

public class Question215 {
    public static void main(String[] args) {
        // Declare variables with names 'nptel', 'space', and 'java' with proper data types.
        String nptel, space, java;

        // Initialize the variables with proper input
        nptel = "NPTEL";
        space = " ";
        java = "JAVA";

        // Print the desired output
        System.out.print(nptel + space + java);
    }
}

Explanation: The code declares and initializes three strings and then prints them concatenated with spaces to get the desired output ‘NPTEL JAVA.’

That wraps up our solutions for Week 2 of your Java NPTEL course. These challenges have introduced you to some advanced Java concepts, including inner classes, method calls, and constructor invocation. Keep practicing and exploring, and you’ll continue to improve your Java programming skills. Stay tuned for more Java NPTEL solutions in the coming weeks!