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Add Two Numbers Using Scanner in Java

beginner· Basics & I/O · I/O

Problem

Console input lets a program read values typed by the user while it's running, instead of relying only on hard-coded values.

Read two integers from the console and print their sum.

Input

4, 7

Output

Sum: 11

Java Program

Java

import java.util.Scanner;

public class SumTwoNumbers {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int a = sc.nextInt(); // reads and parses the typed number
        System.out.println(a); // echo back — this compiler doesn't echo typed input itself
        System.out.print("Enter second number: ");
        int b = sc.nextInt();
        System.out.println(b);
        System.out.println("Sum: " + (a + b));
    }
}

▶ Run Code

Output

Enter first number: 4
Enter second number: 7
Sum: 11

Core Logic

Scanner handles the console input here — read two numbers and add them together.

How It Works

1new Scanner(System.in) creates a reader attached to the console.
2System.out.print(...) shows a prompt without a trailing newline, so the value read next appears to continue that same line.
3sc.nextInt() reads the next number typed and parses it directly into an int.
4System.out.println(a) immediately echoes the value back — most online compilers don't echo typed input themselves the way a real terminal does, so the program prints it explicitly.
5The same read-then-echo pair happens twice — once for each number — and the two ints are added and printed together.

Entering 4 then 7 prints Enter first number: 4, Enter second number: 7, and finally Sum: 11.

💡

Key Point: nextInt() only consumes the numeric token — it leaves the trailing newline in the buffer, which matters if you later mix in a nextLine() call.

Key Concepts

ScannernextInt()console input

Approach 2: BufferedReader

Java

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

public class SumTwoNumbersBufferedReader {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter first number: ");
        // readLine() returns a String, so parse it into an int explicitly
        int a = Integer.parseInt(br.readLine());
        System.out.println(a); // echo back — this compiler doesn't echo typed input itself
        System.out.print("Enter second number: ");
        int b = Integer.parseInt(br.readLine());
        System.out.println(b);
        System.out.println("Sum: " + (a + b));
    }
}

▶ Run Code

Output

Enter first number: 4
Enter second number: 7
Sum: 11

Core Logic

BufferedReader is a common alternative to Scanner — read each line as text, then parse it into a number yourself.

How It Works

1new BufferedReader(new InputStreamReader(System.in)) wraps standard input in a buffered character reader.
2br.readLine() reads one entire line of text at a time, returning it as a String.
3Integer.parseInt(...) converts that string into an int, since readLine() — unlike Scanner.nextInt() — has no built-in numeric parsing.
4System.out.println(a) echoes the parsed value back out, since online compilers typically don't echo typed input themselves the way a real terminal does.
5The method signature adds throws IOException, since readLine() can throw a checked exception on an I/O failure.

Typing 4 then 7 on separate lines parses to the ints 4 and 7, echoed back and followed by Sum: 11.

💡

Key Point: BufferedReader is noticeably faster than Scanner for reading large volumes of input, which is why it's the preferred choice in competitive programming — the trade-off is the extra manual parsing step.

Key Concepts

BufferedReaderreadLine()Integer.parseInt()

Approach 3: Java 8

Java

import java.util.Scanner;
import java.util.function.IntBinaryOperator;

public class SumTwoNumbersLambda {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int a = sc.nextInt();
        System.out.println(a); // echo back — this compiler doesn't echo typed input itself
        System.out.print("Enter second number: ");
        int b = sc.nextInt();
        System.out.println(b);

        // The addition logic is kept separate from how the numbers were read
        IntBinaryOperator add = (x, y) -> x + y;
        System.out.println("Sum: " + add.applyAsInt(a, b));
    }
}

▶ Run Code

Output

Enter first number: 4
Enter second number: 7
Sum: 11

Core Logic

Reading stays the same — Scanner still reads the two typed numbers — but the addition itself is pulled out into a reusable IntBinaryOperator lambda.

How It Works

1Scanner reads a and b exactly as in the direct version, echoing each back.
2IntBinaryOperator add = (x, y) -> x + y; stores the addition logic separately from the input-reading code.
3add.applyAsInt(a, b) combines the two values read from the console, and the result is printed with the same label.

Entering 4 then 7 still prints the same prompts and echoes, with add.applyAsInt(4, 7) producing Sum: 11.

💡

Key Point: Separating 'how the numbers get in' (Scanner) from 'what happens to them' (the lambda) keeps the input logic and the business logic independent — useful once the operation needs to change without touching any input code.