Solution to solve Java iteration exception (IterationException)

Solution to solve Java iteration exception (IterationException)

When programming in Java, we often encounter the problem of iteration exception (IterationException). This exception usually occurs when using an Iterator or an enhanced for loop to traverse a Collection or array.

The reason for iteration exceptions is usually due to modifications to the collection or array during the iteration process. This may result in an invalid index or pointer during the iteration, thus throwing an exception. In order to solve this problem, we can take the following methods.

1. Use a normal for loop instead of an enhanced for loop
   The enhanced for loop is a syntax sugar that simplifies traversing a collection or array. Although it is more concise in code writing, it is recommended to use a normal for loop when we need to modify the collection or array during iteration. This is because in a normal for loop, we can manually control the index to avoid iteration exceptions.

The following is a sample code that uses a normal for loop to solve iteration exceptions:

List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);

for (int i = 0; i < list.size(); i++) {
    if (list.get(i) == 2) {
        list.remove(i);
    }
}

System.out.println(list); // 输出 [1, 3]

2. Use the remove() method of iterator
   Iterator is a method used to Special object for traversing collections. It provides a series of methods to operate on collections, including deleting elements during iteration. Using the iterator's remove() method can safely delete elements in the collection during the iteration process and avoid the occurrence of iteration exceptions.

The following is a sample code that uses the remove() method of the iterator to solve the iteration exception:

List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);

Iterator<Integer> iterator = list.iterator();
while(iterator.hasNext()) {
    int num = iterator.next();
    if(num == 2) {
        iterator.remove();
    }
}

System.out.println(list); // 输出 [1, 3]

3. Use concurrent collection (Concurrent Collection)
   If we need to For iterative operations in a multi-threaded environment, it is recommended to use Concurrent Collection. Concurrent collections are thread-safe and can perform read and write operations on multiple threads at the same time to avoid iteration exceptions.

The following is a sample code for using concurrent collections to solve iteration exceptions:

ConcurrentList<Integer> list = new ConcurrentList<>();
list.add(1);
list.add(2);
list.add(3);

for (Integer num : list) {
    if (num == 2) {
        list.remove(num);
    }
}

System.out.println(list); // 输出 [1, 3]

Summary:
In Java programming, iteration exceptions are a common problem. To solve this problem, we can use a normal for loop instead of the enhanced for loop, use the remove() method of the iterator or use a concurrent collection. These methods can help us avoid the occurrence of iteration exceptions and ensure the correct execution of the program.

No matter which method is used, we should pay attention to avoid modifying the collection or array during the iteration process to avoid exceptions during the iteration process. Reasonable coding standards and careful code review are also important means to avoid iteration anomalies.

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