Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code is designed to interact with the user, taking an integer number as input and then determining whether that number is positive or negative.

Let's break down the logic step-by-step:

1. Import Scanner: The line import java.util.Scanner; tells Java that we want to use the Scanner class, which is part of the java.util package. The Scanner class is essential for reading user input from the console.
2. Class Definition: class prog11 { ... } defines a class named prog11. In Java, all code resides within classes. This class will contain the main logic of our program.
3. Main Method: public static void main (String[]args){ ... } is the entry point of any Java application. When you run this program, execution begins inside this main method.
   • public: Means the method can be accessed from anywhere.
   • static: Means the method belongs to the class itself, not to any specific instance (object) of the class.
   • void: Means the method does not return any value.
   • String[]args: Allows command-line arguments to be passed to the program, though they are not used in this specific code.
4. Create Scanner Object: Scanner input = new Scanner(System.in); creates a new Scanner object named input. We pass System.in to its constructor, which signifies that the Scanner should read input from the standard input stream (usually the keyboard).
5. Prompt User: System.out.print("Enter a number: "); displays the message "Enter a number: " on the console. System.out.print prints the text without moving to the next line, allowing the user to type their input on the same line.
6. Read Input: int num = input.nextInt(); waits for the user to type an integer and press Enter. Once entered, this integer value is read by the nextInt() method of the Scanner object and stored in an integer variable named num.
7. Conditional Check (if-else):
   • if(num>=0){ ... }: This is a conditional statement. It checks if the value stored in num is greater than or equal to zero.
   • If the condition num >= 0 is true (meaning the number is positive or zero), the code inside the if block is executed: System.out.println(num + " is Positive");. This prints the number followed by " is Positive" to the console, and then moves to a new line.
   • else { ... }: If the if condition is false (meaning num is not greater than or equal to zero, hence it must be less than zero), the code inside the else block is executed: System.out.println(num + " is Negative");. This prints the number followed by " is Negative" to the console, and then moves to a new line.
8. Close Scanner: input.close(); is an important step that closes the Scanner object and releases any system resources associated with it. This is good practice to prevent resource leaks.

Algorithm

The algorithm used in this program can be described as follows:

1. Start the program.
2. Initialize a Scanner object to read input from the console.
3. Display a message prompting the user to enter an integer number.
4. Read the integer value entered by the user and store it in a variable.
5. Check the value of the entered number:
   • If the number is greater than or equal to 0, proceed to step 6.
   • Otherwise (if the number is less than 0), proceed to step 7.
6. Print a message indicating that the number is "Positive" (including zero).
7. Print a message indicating that the number is "Negative".
8. Close the Scanner object to release system resources.
9. End the program.