Reading Values from Keyboard in Java

 

Reading Values from Keyboard in Java

In Java, we can take user input from the keyboard using different methods. The most common ways are:

1. Using Scanner Class (Recommended)
2. Using BufferedReader
3. Using Console Class

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1. Using Scanner Class (Most Common & Easy)

The Scanner class is the easiest way to read input from the keyboard. It is part of the java.util package.

Example: Read Integer, Float, and String Input

import java.util.Scanner;  // Import Scanner class

public class ScannerExample {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);  // Create Scanner object
        
        System.out.print("Enter your name: ");
        String name = sc.nextLine();  // Read String input
        
        System.out.print("Enter your age: ");
        int age = sc.nextInt();  // Read integer input

        System.out.print("Enter your salary: ");
        float salary = sc.nextFloat();  // Read float input
        
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Salary: " + salary);
        
        sc.close(); // Close Scanner to prevent memory leak
    }
}

🔹 How It Works?

• sc.nextLine() → Reads a full line (String).
• sc.nextInt() → Reads an integer.
• sc.nextFloat() → Reads a float value.
• sc.close() → Closes the scanner.

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2. Using BufferedReader (Faster, But Complex)

The BufferedReader class reads input efficiently using an input stream. It requires IOException handling.

Example: Read Input using BufferedReader

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

public class BufferedReaderExample {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        System.out.print("Enter your name: ");
        String name = br.readLine();  // Reads string input

        System.out.print("Enter your age: ");
        int age = Integer.parseInt(br.readLine());  // Reads integer input

        System.out.println("Hello " + name + ", your age is " + age);
    }
}

🔹 Why Use BufferedReader?

• Faster than Scanner for large input.
• Requires IOException handling.
• Integer.parseInt() is needed to convert String to int.

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3. Using Console Class (For Secure Input like Passwords)

The Console class is used for reading input securely (like passwords), but it doesn't work in some IDEs (like Eclipse).

Example: Read Input using Console

public class ConsoleExample {
    public static void main(String[] args) {
        java.io.Console console = System.console();

        if (console == null) {
            System.out.println("No console available!");
            return;
        }

        String name = console.readLine("Enter your name: ");
        char[] password = console.readPassword("Enter your password: ");

        System.out.println("Welcome, " + name);
    }
}

🔹 Why Use Console?

• readPassword() hides the password while typing.
• Works in the command line but may not work in IDEs.

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Summary: Best Method for Different Cases

Method	Best For	Works in IDE?	Handles Large Input?
Scanner	Simple user input (int, float, string)	✅ Yes	❌ No
BufferedReader	Faster input processing	✅ Yes	✅ Yes
Console	Secure input (passwords)	❌ No (In most IDEs)	✅ Yes