As a programming language with its fair share of quirks, one of the many things a new Java programmer will run into is the issue of their Scanner.nextLine() calls being ignored. Consider the following Java code:

JavaNextLineProblem.java

import java.util.Scanner;
public class JavaNextLineProblem {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);

		// Prompt the user to enter their name.
		System.out.print("Enter your name: ");
		String name = input.nextLine();

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

		// Prompt the user to enter a description.
		System.out.print("Describe yourself in a sentence: ");
		String description = input.nextLine();

		// Prompt the user to enter a message.
		System.out.print("Enter a message: ");
		String message = input.nextLine();
	}
}

This is the desired result (user input coloured in green):

Enter your name: John
Enter your age: 21
Describe yourself in a sentence: I am awesome.
Enter a message: Hello world!

However, this is what you actually get:

Enter your name: John
Enter your age: 21
Describe yourself in a sentence: Enter a message: Hello world!

The program skips over the collection of input for the Describe yourself in a sentence prompt, and goes straight into collecting the input for the Enter a message prompt. What’s going on?