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Java Program: Input Validation - Numeric Only

Java

import java.util.Scanner;
 
public class NumericInputValidation {
    public static void main(String[] args) {
 
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number: ");
 
        // Check if input is numeric
        if (sc.hasNextInt()) {
            int number = sc.nextInt();
            System.out.println("Valid number entered: " + number);
        }
        else if (sc.hasNextDouble()) {
            double number = sc.nextDouble();
            System.out.println("Valid number entered: " + number);
        }
        else {
            System.out.println("Invalid input! Please enter numeric values only.");
        }
 
        sc.close();
    }
}

Output

 
OUTPUT 1: Integer Input
Enter a number: 123
Valid number entered: 123 

OUTPUT 2: Floating Point Input
Enter a number: 45.67
Valid number entered: 45.67
 
OUTPUT 3: Invalid Input
Enter a number: abc
Invalid input! Please enter numeric values only.

Explanation

✅ 1. Scanner Methods

hasNextInt() → checks if the next token is an integer
hasNextDouble() → checks if the next token is a floating-point number

✅ 2. Why Input Validation?

Prevents runtime errors when parsing non-numeric input
Ensures only valid numeric values are processed

✅ 3. Flow

Ask the user for input
Check using hasNextInt() → integer
Else check hasNextDouble() → floating number
Else → invalid input message

Java Programs

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Introduction to Java

Java Program: Input Validation - Numeric Only

Output

Explanation