How to Properly Read Values from Keyboard into an Array in Java

Learn how to read numbers from the keyboard and store them in an array in Java, avoiding common errors like ArrayIndexOutOfBoundsException.
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How to Properly Read Values from Keyboard into an Array in Java

If you're delving into Java programming, you might find yourself needing to read values from the keyboard and store them in an array. However, as many new programmers discover, this simple task can sometimes lead to frustrating errors. One such error is the notorious ArrayIndexOutOfBoundsException, which can occur if you're not careful with your array size and input handling. In this post, we'll explore a common issue and how to resolve it, ensuring that you can confidently read input values into an array without running into problems.

The Problem

Let's say you want to enter numbers from the keyboard to save them into an array named fraction. A typical attempt might look like this:

[[See Video to Reveal this Text or Code Snippet]]

When you run this code, you might encounter an error message like:

[[See Video to Reveal this Text or Code Snippet]]

This happens because you're trying to assign a value to fraction[1], but your fraction array only has one element (fraction[0]). Hence, let's dive into how to correct this issue properly.

The Solution

To fix the error and successfully read two numbers into the fraction array, we need to make a couple of adjustments in the code:

Step 1: Adjust the Size of the Array

First, instead of initializing fraction as an array with one element (int[] fraction = new int[1];), we should set its size to two, since we want to store two integer values:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Stream Reader Setup

You should also ensure that the input stream reader is effectively managed. It's best to open the InputStreamReader once and use a Scanner for input as it simplifies reading different types of input. Additionally, using try-with-resources will ensure that resources are closed automatically.

Step 3: Updated Code

With these adjustments in mind, here's the improved version of your method:

[[See Video to Reveal this Text or Code Snippet]]

Key Takeaways

Array Size Matters: Ensure your array size corresponds to the number of inputs you expect.

Manage Input Streams: Use try-with-resources to manage your streams effectively, preventing resource leaks and making your code cleaner.

Use Scanner for Easy Input Handling: A Scanner simplifies reading various data types from input.

Now you can confidently read multiple values from the keyboard into your array without running into the dreaded ArrayIndexOutOfBoundsException. Happy coding!