java do-while loop with user input

java do-while loop with user input

Here's an example of a Java do-while loop that takes user input:

import java.util.Scanner;
public class UserInputDoWhile {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int number;
do {
System.out.print("Enter a positive integer: ");
if (scanner.hasNextInt()) {
number = scanner.nextInt();
if (number > 0) {
System.out.println("You entered: " + number);
break; // Exit the loop
} else {
System.out.println("Please enter a positive integer.");
}
} else {
System.out.println("Invalid input. Please try again.");
scanner.next(); // Clear the invalid input
}
} while (true);
System.out.print("Now, enter your favorite color (1-3): ");
int choice;
do {
if (scanner.hasNextInt()) {
choice = scanner.nextInt();
if (choice >= 1 && choice <= 3) {
switch (choice) {
case 1:
System.out.println("You chose Red.");
break;
case 2:
System.out.println("You chose Green.");
break;
case 3:
System.out.println("You chose Blue.");
break;
}
break; // Exit the loop
} else {
System.out.println("Please enter a number between 1 and 3.");
}
} else {
System.out.println("Invalid input. Please try again.");
scanner.next(); // Clear the invalid input
}
} while (true);
scanner.close();
}
}

Let's go through what this code does:

First, we create a Scanner object called scanner to read user input from the console.

Next, we have our first do-while loop. We prompt the user to enter a positive integer. If the input is valid (i.e., an integer greater than 0), we print out a message and exit the loop using the break statement. If the input is invalid (e.g., not an integer or negative), we print out an error message, clear the invalid input with scanner.next(), and continue looping.

Once the user enters a valid positive integer, the program continues to the next prompt: "Now, enter your favorite color (1-3):". This time, we have another do-while loop. We again read user input using scanner.nextInt() and check if it's within the range of 1 to 3 (inclusive). If the input is valid, we use a switch statement to print out a message based on the chosen color and exit the loop with break. If the input is invalid, we print out an error message, clear the invalid input with scanner.next(), and continue looping.

Finally, when the user enters a valid favorite color choice, the program prints out a corresponding message and then closes the Scanner object to release system resources.

This code demonstrates how you can use do-while loops in Java to repeatedly ask for user input until it meets certain criteria.

How to print 1 to 100 with while loop in Java?

I'm happy to help you with that! Here's a step-by-step guide on how to print the numbers from 1 to 100 using a while loop in Java:

Code:

public class PrintNumbers {
public static void main(String[] args) {
int number = 1;
while (number <= 100) {
System.out.println(number);
number++;
}
}
}

Let's break down the code:

How it works:

When you run this program, the output will be a list of numbers from 1 to 100, printed one after another:

1
2
3
...
98
99
100

Here's what happens behind the scenes:

The loop continues until number reaches 100, at which point the condition becomes false, and the loop exits.

Tips and Variations:

I hope this helps! Let me know if you have any questions or need further clarification.