09 — User Input

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▶️ java pkg1core/core24UserInput.java

Scanner — easiest for beginners

1Scanner sc = new Scanner(System.in);2System.out.print("Name: ");3String name = sc.nextLine();4 5System.out.print("Age: ");6int age = sc.nextInt();7sc.nextLine();   // consume leftover newline — IMPORTANT!

⚠️ Classic bug: nextInt() then nextLine() — the nextLine() reads an empty string because the newline after the number is still in the buffer. Call nextLine() once to consume it.

BufferedReader — faster for large text

1BufferedReader br = new BufferedReader(new InputStreamReader(System.in));2String line = br.readLine();

Preferred for reading many lines from files or stdin in production.

Mini project idea

Combine everything from Part 1:

11. Ask user name and age (Scanner)22. Validate age > 0 (if/else)33. Store scores in an array44. Print average with formatted String

Practice

1. Run core24UserInput (uses simulated input — read the code).
2. Uncomment the interactive section and try with real keyboard input.
3. Build the mini project above.

Milestone: You completed Java Basics (chapters 01–09). 🎉

Next → 10 Classes & Objects Related → 01 Core Java