Practice Questions — Taking Input with Scanner

import java.util.Scanner;

public class TempConverter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter temperature in Celsius: ");
        double celsius = sc.nextDouble();
        double fahrenheit = (celsius * 9.0 / 5.0) + 32;
        System.out.printf("%.1f C = %.2f F%n", celsius, fahrenheit);
        sc.close();
    }
}

import java.util.Scanner;

public class ReportCard {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter roll number: ");
        int roll = sc.nextInt();
        sc.nextLine();
        System.out.print("Enter name: ");
        String name = sc.nextLine();
        System.out.print("Enter marks in 3 subjects: ");
        int m1 = sc.nextInt();
        int m2 = sc.nextInt();
        int m3 = sc.nextInt();
        int total = m1 + m2 + m3;
        double avg = total / 3.0;
        System.out.println("Name: " + name);
        System.out.println("Roll: " + roll);
        System.out.println("Total: " + total);
        System.out.printf("Average: %.2f%n", avg);
        System.out.println("Result: " + (avg >= 40 ? "Pass" : "Fail"));
        sc.close();
    }
}

import java.util.Scanner;

public class WordCounter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a sentence: ");
        String sentence = sc.nextLine().trim();
        if (sentence.isEmpty()) {
            System.out.println("Word count: 0");
        } else {
            String[] words = sentence.split("\\s+");
            System.out.println("Word count: " + words.length);
        }
        sc.close();
    }
}

import java.util.Scanner;

public class SumOfN {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter N: ");
        int n = sc.nextInt();
        System.out.print("Enter " + n + " numbers: ");
        int sum = 0;
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        for (int i = 0; i < n; i++) {
            int num = sc.nextInt();
            sum += num;
            if (num < min) min = num;
            if (num > max) max = num;
        }
        System.out.println("Sum: " + sum);
        System.out.println("Min: " + min);
        System.out.println("Max: " + max);
        sc.close();
    }
}

import java.util.Scanner;

public class ValidInput {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = 0;
        boolean valid = false;
        while (!valid) {
            System.out.print("Enter a number (1-100): ");
            if (sc.hasNextInt()) {
                num = sc.nextInt();
                if (num >= 1 && num <= 100) {
                    valid = true;
                } else {
                    System.out.println("Out of range!");
                }
            } else {
                System.out.println("Invalid!");
                sc.next(); // consume invalid token
            }
        }
        System.out.println("You entered: " + num);
        sc.close();
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

public class MultiLineProcessor {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine().trim());
        for (int i = 1; i <= n; i++) {
            String line = br.readLine();
            System.out.println("Line " + i + ": " + line + " (" + line.length() + " chars)");
        }
        br.close();
    }
}

import java.util.Scanner;

public class SpaceSeparated {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine().trim();
        if (line.isEmpty()) {
            System.out.println("No input provided.");
        } else {
            String[] parts = line.split("\\s+");
            int sum = 0;
            int count = parts.length;
            for (String part : parts) {
                sum += Integer.parseInt(part);
            }
            double avg = (double) sum / count;
            System.out.println("Count: " + count);
            System.out.println("Sum: " + sum);
            System.out.println("Average: " + avg);
        }
        sc.close();
    }
}

import java.util.Scanner;

public class MenuCalc {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        boolean running = true;
        while (running) {
            System.out.println("\n1. Add  2. Subtract  3. Multiply  4. Divide  5. Exit");
            System.out.print("Choice: ");
            int choice = sc.nextInt();
            if (choice == 5) {
                System.out.println("Goodbye!");
                running = false;
            } else if (choice >= 1 && choice <= 4) {
                System.out.print("Enter two numbers: ");
                double a = sc.nextDouble();
                double b = sc.nextDouble();
                switch (choice) {
                    case 1: System.out.println("Result: " + (a + b)); break;
                    case 2: System.out.println("Result: " + (a - b)); break;
                    case 3: System.out.println("Result: " + (a * b)); break;
                    case 4:
                        if (b == 0) System.out.println("Error: Division by zero!");
                        else System.out.println("Result: " + (a / b));
                        break;
                }
            } else {
                System.out.println("Invalid choice!");
            }
        }
        sc.close();
    }
}