Input in Java Programming

Input in Java

The Scanner class is used in Java programs to accept input from the standard input device (keyboard) and store it in one or more variables. The Scanner class is available in the java.util package.

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To use the Scanner class, we need to create an object of the Scanner class and use the available methods in the class to take different types of input from the user. The available methods in the Scanner class are listed below.

Let's see an example of how to use Scanner class to read different types of data from the keyboard.

import java.util.Scanner;  // Import the Scanner class

public class Example
{
    public static void main(String[] args)
    {
        int age;
        float height;
        double weight;
        char initial;

        // Create a Scanner object to read input
        Scanner sc = new Scanner(System.in);

        // Ask the user to enter their age
        System.out.print("Enter your age: ");
        age = sc.nextInt();

        // Ask the user to enter their height
        System.out.print("Enter your height in meters: ");
        height = sc.nextFloat();

        // Ask the user to enter their weight
        System.out.print("Enter your weight in kilogram: ");
        weight = sc.nextDouble();

        // Consume the newline character left by the sc.nextDouble()
        sc.nextLine();  // This fixes the issue

        // Ask the user to enter the first character of their name
        System.out.print("Enter the first character of your name: ");
        initial = sc.nextLine().charAt(0);	// Reads the first character from input

        // Print the values entered by the user
        System.out.println("\nYou entered:");
        System.out.println("Age: " + age);
        System.out.println("Height: " + height);
        System.out.println("Weight: " + weight);
        System.out.println("Initial: " + initial);
    }
}

Enter your age: 15
Enter your height in meters: 3.423
Enter your weight in kilogram: 45.21543
Enter the first character of your name: R

You entered:
Age: 15
Height: 3.423
Weight: 45.21543
Initial: R                               

1. Prompting the User:

System.out.print is used to ask the user to enter their age, height, weight, and initial.

2. Reading Input:

age = sc.nextInt(); reads an integer type number input by the user and stores it in the variable age.

height = sc.nextFloat(); reads a float type number input by the user and stores it in the variable height.

weight = sc.nextDouble(); reads a double type number input by the user and stores it in the variable weight.

sc.nextLine() consume the newline character left by the sc.nextDouble().

initial = sc.nextLine().charAt(0); reads the first character from the user input and stores it in the variable initial.

3. Displaying the Input:

System.out.println() shows the values entered by the user, confirming they were read correctly.