Accepting Input from the Keyboard

Accepting Input from the Keyboard

1. Big Picture (beginner)

Java reads keyboard via stream: System.in (bytes) → wrapper (Scanner easiest, BufferedReader fastest) → your variables. Exams expect Scanner (simple) + know alternatives exist.

2. Three Ways (exam table)

Way	Code hint	Beginner verdict
Scanner (easiest)	new Scanner(System.in)	USE THIS (all examples here)
BufferedReader	new BufferedReader(new InputStreamReader(System.in))	fast, but readLine + parse + throws
Console / args	System.console(), args[0]	special cases (passwords, CLI)

3. Minimal Pattern (memorize!)

import java.util.Scanner;
public class Input {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in); // connect keyboard
        System.out.print("Enter age: ");
        int age = sc.nextInt();              // read
        System.out.println("next year: " + (age + 1));
        sc.close(); // free keyboard
    }
}

4. Golden Rules

• import java.util.Scanner; at top (else ERROR).
• Prompt BEFORE read (print, not println — cursor stays!).
• close() once at end. One Scanner per program (don't make two on System.in!).

5. Exam Points

• Three ways + Scanner program — 5 marks, very frequent.
• Import + close rules — 2-3 marks, frequent.