Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code demonstrates the fundamental concepts of Object-Oriented Programming (OOP) by defining a Student class and then creating multiple objects (instances) of that class.

1. class Student Definition: The first part of the code defines a blueprint named Student. This blueprint describes what characteristics a student will have (their name, rollno, and marks) and what actions they can perform (a display() method to show their details).

   • String name, rollno;: These are "data members" or "attributes" that will hold text values for a student's name and roll number.
   • double marks;: This data member will hold a decimal number for a student's marks.
   • void display(): This is a "method" or "behavior." When called, it prints the specific name, rollno, and marks of the student object it's called on to the console.

2. class progx1 and main method: The second class, progx1, contains the main method. In Java, the main method is the entry point where the program execution begins.

   • Student s1 = new Student();: Inside main, the first line creates a new Student object from the Student blueprint. This object is given a name, s1, which acts as a reference to it in memory.
   • Student s2 = new Student();: Similarly, a second distinct Student object is created and referenced by s2. At this point, s1 and s2 are separate entities, each with their own name, rollno, and marks attributes, though initially these attributes have default values (null for String, 0.0 for double).
   • Assigning Values: The next lines assign specific values to the attributes of each student object:
     • s1.name = "Nathan"; assigns "Nathan" to the name attribute of the s1 object.
     • s1.rollno = "25LEC07"; assigns "25LEC07" to s1's roll number.
     • s1.marks = 9; assigns 9.0 to s1's marks.
     • The same process is repeated for s2, assigning "Ashwin", "25LEC01", and 10 to its respective attributes.
   • Calling Methods:
     • s1.display();: This line calls the display() method on the s1 object. This will execute the code within s1's display() method, printing "Nathan", "25LEC07", and 9.0.
     • s2.display();: This line then calls the display() method on the s2 object, which will print "Ashwin", "25LEC01", and 10.0.

In essence, the code defines what a "student" is (a class), then creates two specific "students" (objects) with their own unique data, and finally asks each student object to display its own information.

Algorithm

The algorithm implemented in this Java code can be broken down into the following steps:

1. Define a Student Class:

   • Declare a class named Student.
   • Inside the Student class, declare three instance variables: name (String), rollno (String), and marks (double).
   • Declare a method named display() within the Student class.
   • Inside the display() method, print the values of the name, rollno, and marks instance variables, each on a new line with descriptive labels.

2. Define a Main Class:

   • Declare a class named progx1 to contain the main execution logic.
   • Inside progx1, define the main method (the program's entry point).

3. Create Student Objects:

   • Inside the main method, create the first Student object using new Student() and assign it to a reference variable s1.
   • Create the second Student object using new Student() and assign it to a reference variable s2.

4. Assign Data to s1:

   • Set the name attribute of s1 to "Nathan".
   • Set the rollno attribute of s1 to "25LEC07".
   • Set the marks attribute of s1 to 9.

5. Assign Data to s2:

   • Set the name attribute of s2 to "Ashwin".
   • Set the rollno attribute of s2 to "25LEC01".
   • Set the marks attribute of s2 to 10.

6. Display s1's Details:

   • Call the display() method on the s1 object.

7. Display s2's Details:

   • Call the display() method on the s2 object.