Java Error: Java8 Stream Error, How to Handle and Avoid

In the process of using Java programming, you may encounter Java8 Stream errors. This type of error may be difficult to troubleshoot and solve, causing great trouble to developers. So how to deal with and avoid Java8 Stream errors? This article will introduce it from the following aspects.

1. Introduction to Java8 Stream

Java Stream is a new API added in Java 8. It allows developers to perform some complex operations on certain collections, such as filtering, mapping, sorting, etc. . When using Java Stream, the data stream can be converted into different data types to perform various operations. These operations can be executed in parallel, greatly improving the efficiency of the program.

2. Common Java8 Stream error types

1. UnsupportedOperationException

When using Java Stream, one of the most common errors is UnsupportedOperationException. This error usually occurs when trying to modify a collection generated by a Java Stream.

For example, when we use the Stream.of() method, we will get a Stream object, but we cannot directly perform add() or remove() operations on this object, otherwise UnsupportedOperationException will be thrown.

2. IllegalStateException

Another common error is IllegalStateException. This error usually occurs when you are still trying to operate on the Java Stream object after it has been closed. For example, if we have used the Stream.close() method to close the stream, but there is still code to operate on it afterwards, an IllegalStateException will be thrown.

3. ClassCastException

Another common error is ClassCastException, which usually occurs when trying to convert a stream to the wrong data type. For example, when we try to convert a stream composed of Integers to String type, a ClassCastException will be thrown.

3. How to deal with Java8 Stream errors

1. Use try-catch statement to catch exceptions

When a Java8 Stream error occurs, we can use try-catch Statement catches exceptions. In this way, we can output the corresponding error message when an exception occurs and prevent the program from interrupting. For example:

try {
List list = Arrays.asList("a", "b", null, "d");
long count = list.stream(). filter(Objects::nonNull).count();
System.out.println(count);
} catch (NullPointerException e) {
System.out.println("A NullPointerException occurred!") ;
}

2. Explicitly check whether the stream is null

When using Java8 Stream operation, we can also explicitly check whether the stream is null, This avoids the occurrence of NullPointerException. For example:

List list = Arrays.asList("a", "b", null, "d");
long count = list == null ? 0 : list.stream( ).filter(Objects::nonNull).count();
System.out.println(count);

3. Avoid operating on closed streams

When the Java Stream object has been closed, we need to avoid operating on it, otherwise an IllegalStateException will be thrown. Therefore, before performing stream operations, we should check whether the stream has been closed, for example:

Stream stream = Arrays.asList("a", "b", "c").stream ();
if (stream.isParallel()) {
stream.close();
}

4. How to avoid Java8 Stream errors

1. Avoid performing add() or remove() operations on Stream objects

Since Java8 Stream objects are immutable, we should avoid performing add() or remove() operations on them if If we really need to do this, we can use other mutable collection types to save the data and then convert it to a Java8 Stream object.

2. Avoid using wrong data types

When we convert a stream to a different data type, we should ensure that the data type is correct, otherwise ClassCastException will be thrown abnormal. Therefore, when performing type conversion, we need to carefully check whether the data type is correct. If we are not sure, we can use the type checking syntax in Java to judge.

3. Close the stream in time

When using Java8 Stream operation, we need to close the stream in time, otherwise it will occupy resources and may cause errors. Therefore, after the operation is completed, we need to explicitly close the stream, such as using try-resource to close the stream.

To sum up, Java8 Stream errors are common problems encountered in Java programming. We need to carefully handle and avoid these errors to ensure the normal operation and efficient performance of the program.

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