Console Input and Output Operations

Displaying Output to Console

Basic Syntax:

System.out.println(message); // Output with newline
System.out.print(message);  // Output without newline  
System.out.printf(format, message); // Formatted output

• println automatically apppends \n while print does not
• printf follows similar formatting rules as C language printf

Code Examples:

System.out.println("Hello World");
int value = 42;
System.out.printf("%d", value);

Format Specifiers:

Reading Input from Keyboard

Using Scanner for String/Integer/Float Input:

import java.util.Scanner;

Scanner inputReader = new Scanner(System.in);
System.out.println("Enter your name:");
String userName = inputReader.nextLine();
System.out.println("Enter your age:");
int userAge = inputReader.nextInt();
System.out.println("Enter your salary:");
float userSalary = inputReader.nextFloat();

System.out.println("User Details:");
System.out.println("Name: " + userName);
System.out.println("Age: " + userAge);
System.out.println("Salary: " + userSalary);

inputReader.close();

Reading Multiple Numbers and Calculating Average:

Scanner scanner = new Scanner(System.in);
double total = 0;
int count = 0;

while (scanner.hasNextDouble()) {
    double number = scanner.nextDouble();
    total += number;
    count++;
}

System.out.println("Total: " + total);
System.out.println("Average: " + (total / count));
scanner.close();

Important Notes:

• Use Ctrl+Z (Windows) or Ctrl+D (Linux/Mac) to terminate input during multiple data entry
• Always close the Scanner object when done

Number Guessing Game Implementation

Game Rules

The system genreates a random number between 1 and 100. The player inputs guesses, receiving "Too low", "Too high", or "Correct guess" feedback until the correct number is found.

Complete Implementation

import java.util.Random;
import java.util.Scanner;

public class NumberGame {
    public static void main(String[] args) {
        Random generator = new Random();
        Scanner input = new Scanner(System.in);
        
        int targetNumber = generator.nextInt(100) + 1;
        
        while (true) {
            System.out.println("Guess a number (1-100):");
            int userGuess = input.nextInt();
            
            if (userGuess < targetNumber) {
                System.out.println("Too low");
            } else if (userGuess > targetNumber) {
                System.out.println("Too high");
            } else {
                System.out.println("Correct! You guessed it.");
                break;
            }
        }
        input.close();
    }
}

Implementation Breakdown

1. Import Required Libraries: Random for number generation and Scanner for user input
2. Class Definition: Main class containing the program entry point
3. Initialization: Create Random and Scanner objects
4. Target Generation: Generate random number between 1-100 using nextInt(100) + 1
5. Game Loop: Continuous loop until correct guess
   • Prompt user for number input
   • Compare guess with target number
   • Provide appropriate feedback
   • Break loop when guess matches target
6. Resource Cleanup: Close Scanner to release system resources