Class ArrayIndexOutOfBoundsException
The index is included in this exception’s detail message. The exact presentation format of the detail message is unspecified.
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Ошибка ArrayIndexOutOfBoundsException Java
ArrayIndexOutOfBoundsException – это исключение, появляющееся во время выполнения. Оно возникает тогда, когда мы пытаемся обратиться к элементу массива по отрицательному или превышающему размер массива индексу. Давайте посмотрим на примеры, когда получается ArrayIndexOutOfBoundsException в программе на Java.
Попробуйте выполнить такой код:
Вы увидите ошибку:
Что здесь произошло? Ошибка в строке 27 – мы вызвали метод deposit(), а в нем уже, в строке 22 – попытались внести в поле массива значение «deposit». Почему выкинуло исключение? Дело в том, что мы инициализировали массив размера 11 (number = 11), н опопытались обратиться к 12-му элементу. Нумерация элементов массива начинается с нуля. Так что здесь надо сделать, например, так
Но вообще, это плохой код, так писать не надо. Давайте рассмотрим еще один пример возникновения ошибки ArrayIndexOutOfBoundsException:
Здесь массив заполняется случайными значениями. При выполнении IntelliJ IDEA выдаст ошибку
В строке 37 мы заносим значение в массив. Ошибка возникла помтому, что индекса 10 нет в массиве arr, поэтому условие цикла i <= arr.length надо поменять на i < arr.length
Конструкция try для ArrayIndexOutOfBoundsException
ArrayIndexOutOfBoundsException можно обработать с помощью конструкции try-catch. Для этого оберните try то место, где происходит обращение к элементу массива по индексу, например, заносится значение. Как-то так:
Но я бы рекомендовал вам все же не допускать данной ошибки, писать код таким образом, чтобы не пришлось ловить исключение ArrayIndexOutOfBoundsException.
Автор этого материала — я — Пахолков Юрий. Я оказываю услуги по написанию программ на языках Java, C++, C# (а также консультирую по ним) и созданию сайтов. Работаю с сайтами на CMS OpenCart, WordPress, ModX и самописными. Кроме этого, работаю напрямую с JavaScript, PHP, CSS, HTML — то есть могу доработать ваш сайт или помочь с веб-программированием. Пишите сюда.
заметки, ArrayIndexOutOfBoundsException, java, ошибки, исключения
How to Fix the Array Index Out Of Bounds Exception in Java
The ArrayIndexOutOfBoundsException is a runtime exception in Java that occurs when an array is accessed with an illegal index. The index is either negative or greater than or equal to the size of the array.
Since the ArrayIndexOutOfBoundsException is an unchecked exception, it does not need to be declared in the throws clause of a method or constructor.
What Causes ArrayIndexOutOfBoundsException
The ArrayIndexOutOfBoundsException is one of the most common errors in Java. It occurs when a program attempts to access an invalid index in an array i.e. an index that is less than 0, or equal to or greater than the length of the array.
Since a Java array has a range of [0, array length — 1], when an attempt is made to access an index outside this range, an ArrayIndexOutOfBoundsException is thrown.
ArrayIndexOutOfBoundsException Example
Here is an example of a ArrayIndexOutOfBoundsException thrown when an attempt is made to retrieve an element at an index that falls outside the range of the array:
In this example, a String array of length 10 is created. An attempt is then made to access an element at index 10, which falls outside the range of the array, throwing an ArrayIndexOutOfBoundsException :
How to Fix ArrayIndexOutOfBoundsException
To avoid the ArrayIndexOutOfBoundsException , the following should be kept in mind:
- The bounds of an array should be checked before accessing its elements.
- An array in Java starts at index 0 and ends at index length — 1 , so accessing elements that fall outside this range will throw an ArrayIndexOutOfBoundsException .
- An empty array has no elements, so attempting to access an element will throw the exception.
- When using loops to iterate over the elements of an array, attention should be paid to the start and end conditions of the loop to make sure they fall within the bounds of an array. An enhanced for loop can also be used to ensure this.
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How to Fix Java Error java.lang.ArrayIndexOutOfBoundsException
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In this article, you will learn the main reason why you will face the java.lang.ArrayIndexOutOfBoundsException Exception in Java along with a few different examples and how to fix it.
I think it is essential to understand why this error occurs, since the better you understand the error, the better your ability to avoid it.
This tutorial contains some code examples and possible ways to fix the error.
Watch the tutorial on Youtube:
Table of Contents
What causes a java.lang.ArrayIndexOutOfBoundsException?
The java.lang.ArrayIndexOutOfBoundsException error occurs when you are attempting to access by index an item in indexed collection, like a List or an Array. You will this error, when the index you are using to access doesn’t exist, hence the “Out of Bounds” message.
To put it in simple words, if you have a collection with four elements, for example, and you try to access element number 7, you will get java.lang.ArrayIndexOutOfBoundsException error.
To help you visualise this problem, you can think of arrays and index as a set of boxes with label, where every label is a number. Note that you will start counting from 0.
For instance, we have a collection with three elements, the valid indexes are 0,1 and 2. This means three boxes, one label with 0, another one with 1, and the last box has the label 2. So if you try to access box number 3, you can’t, because it doesn’t exist. That’s when you get the java.lang.ArrayIndexOutOfBoundsException error.
The Simplest Case
Let’s see the simplest code snippet which will through this error:
Although the error refer to arrays, you could also encounter the error when working with a List, which is also an indexed collection, meaning a collection where item can be accessed by their index.
Example #1: Using invalid indexes in a loop
An instance where you might encounter the ArrayIndexOutOfBoundsException exception is when working with loops. You should make sure the index limits of your loop are valid in all the iterations. The loop shouldn’t try to access an item that doesn’t exist in the collection. Let’s see an example.
The code above will loop through every item in the list and print its value, however there is an exception at the end. The problem in this case is the stopping condition in the loop: index<=fruits.size() . This means that it will while index is less or equal to 3, therefore the index will start in 0, then 1, then 2 and finally 3, but unfortunately 3 is invalid index.
How to fix it – Approach #1
You can fix this error by changing the stopping condition. Instead of looping while the index is less or equal than 3, you can replace by “while index is less than 3”. Doing so the index will go through 0, 1, and 2, which are all valid indexes. Therefore the for loop should look as below:
That’s all, really straightforward change once you understand the root cause of the problem. Here is how the code looks after the fix:
How to fix it – Approach #2
Another way to avoid this issue is using the for each syntax. Using this approach, you don’t have to manage the index, since Java will do it for you. Here is how the code will look:
Example #2: Loop through a string
Another example. Imagine that you want to count the appearances of character ‘a’ in a given sentence. You will write a piece of code similar to the one below:
The issue in this case is similar to the one from the previous example. The stopping condition is the loop is right. You should make sure the index is within the boundaries.
How to fix it
As in the previous example, you can fix it by removing the equal from the stopping condition, or by using a foreach and therefore avoid managing the index. See below both fixes:
Conclusion
In summary, we have seen what the “java.lang.ArrayIndexOutOfBoundsException” error means . Additionally we covered how you can fix this error by making sure the index is within the collection boundaries, or using foreach syntax so you don’t need to manage the index.
I hope you enjoy this article, and understand this issue better to avoid it when you are programming.