BufferedReaderInput.java

package Phase0_SetupAndFirstPrograms.Input;

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

/**
 * <h1>Taking Input &mdash; java.io.BufferedReader</h1>
 *
 * <p><code>BufferedReader</code> is the older (pre-Java-5) way to read input. It reads one whole
 * LINE at a time as a String &mdash; you have to parse the result yourself.</p>
 *
 * <h2>Why use BufferedReader over Scanner?</h2>
 * <ul>
 *   <li>Faster than <code>Scanner</code> because it does not do regex-based tokenizing.
 *       Commonly used in competitive programming for that reason.</li>
 *   <li>Larger buffer size by default (8192 chars vs Scanner's 1024).</li>
 * </ul>
 *
 * <h2>Trade-offs</h2>
 * <ul>
 *   <li>Returns Strings only. You must convert with <code>Integer.parseInt()</code>,
 *       <code>Double.parseDouble()</code>, etc.</li>
 *   <li>Throws checked <code>IOException</code>, so you must declare "throws" or wrap in try/catch.</li>
 *   <li>No built-in support for reading individual tokens of different types from the
 *       same line (you would split the line yourself).</li>
 * </ul>
 *
 * @author  Deepak Gupta
 * @version 1.0
 * @since 2026-05-21
 */

public class BufferedReaderInput {

    public static void main(String[] args) throws IOException {
        // System.in is a byte stream. We wrap it with InputStreamReader to convert
        // bytes -> chars, and then with BufferedReader to read line-by-line efficiently.
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        // 1) Read a full line as a String
        System.out.print("Enter your full name: ");
        String name = br.readLine();

        // 2) Read a number - need explicit parsing
        System.out.print("Enter your age      : ");
        int age = Integer.parseInt(br.readLine());

        // 3) Read multiple tokens from one line - split manually
        System.out.print("Enter three numbers separated by spaces: ");
        String[] tokens = br.readLine().split("\\s+");
        int a = Integer.parseInt(tokens[0]);
        int b = Integer.parseInt(tokens[1]);
        int c = Integer.parseInt(tokens[2]);

        System.out.println();
        System.out.println("Hello " + name + ", age " + age);
        System.out.println("Sum of the three numbers = " + (a + b + c));

        br.close();

        // SAMPLE RUN
        // Enter your full name: Deepak Gupta
        // Enter your age      : 25
        // Enter three numbers separated by spaces: 10 20 30
        //
        // Hello Deepak Gupta, age 25
        // Sum of the three numbers = 60
    }
}