How to handle OutOfMemoryError exception in Java?

Java is a very popular programming language. Due to its high portability, object-oriented features and excellent performance, it is widely used in fields such as enterprise-level application development and mobile application development. However, in the process of Java application development, OutOfMemoryError exceptions are often encountered, which is an error caused by excessive application memory usage. This article will introduce the cause, identification and how to deal with this exception.

1. What is OutOfMemoryError exception?

OutOfMemoryError exception is an exception thrown by the Java virtual machine when it cannot apply for enough memory space. In Java application development, generally speaking, the memory space allocated to the Java virtual machine is limited. When the memory used and allocated by the application exceeds the preset threshold, an OutOfMemoryError exception will occur. It should be noted here that the memory space allocated by the Java virtual machine is limited, and the operating system itself also has limitations.

2. Cause of OutOfMemoryError exception

The memory requested by Java applications can be divided into three parts: heap memory, stack memory and non-heap memory. Among them, heap memory is the main memory space used by all applications, while stack memory and non-heap memory are used to store thread calls and the memory storage of the Java virtual machine itself.

When the memory described exceeds the memory size that the Java virtual machine can allocate, an OutOfMemoryError exception will occur. The following are several reasons that may cause this exception:

1. Insufficient heap memory - due to excessive use of heap memory by the application, such as creating too many large objects, etc., resulting in insufficient heap memory, thus triggering the OutOfMemoryError exception .

2. Insufficient non-heap memory - This situation is usually caused by the application using too many classes, or the class or JAR package file used is too large, thus consuming the non-heap allocated by the Java virtual machine. memory space.

3. Stack memory overflow - When the stack memory used by a thread exceeds the upper limit allocated by the Java virtual machine, a StackOverflowError exception will be thrown. When the stack memory used by the thread reaches the maximum capacity of the Java virtual machine stack, an OutOfMemoryError exception will be thrown.

3. Identify the OutOfMemoryError exception

When the Java application is running, if the following exception message appears, it means that the Java application has experienced an OutOfMemoryError exception:

java.lang. OutOfMemoryError: Java heap space

This information means that the heap memory is insufficient, and the developer needs to add some heap memory optimization measures to the program, or increase the Java virtual machine heap memory size.

java.lang.OutOfMemoryError: unable to create new native thread

This message means that there are too many threads and the Java virtual machine cannot create any new threads. It needs to be solved by adjusting the number of threads used or increasing the non-heap memory allocated by the Java virtual machine.

java.lang.OutOfMemoryError: PermGen space

This message means that non-heap memory overflows, and memory usage needs to be reduced by adjusting the size of non-heap memory or using optimization techniques.

4. Handling the OutOfMemoryError exception

When dealing with the OutOfMemoryError exception in a Java application, developers can solve it through the following methods:

1. Add Java virtualization Heap memory capacity allocated by the machine: Use the "-Xmx" command line parameter to increase the heap memory capacity of the Java virtual machine, but you need to take into account the actual available memory of the system.

2. Adjust the garbage collection mechanism of the Java virtual machine: Improve the usage efficiency of heap memory by optimizing the garbage collection mechanism, thereby reducing the burden caused by garbage collection.

3. Reduce memory usage by optimizing code: Reduce memory usage by optimizing code, such as using connection pools, avoiding creating a large number of objects, using basic types as much as possible, and other techniques.

4. Increase the non-heap memory capacity of the Java virtual machine: Increase the non-heap memory space of the Java virtual machine through the "-XX:MaxPermSize" command line parameter, but you also need to take into account the limitations of the actual available memory.

In short, when dealing with OutOfMemoryError exceptions in Java programs, you need to fully understand the reasons and mechanisms behind the exceptions in order to take the correct handling method. Hope this article is helpful to you.

The above is the detailed content of How to handle OutOfMemoryError exception in Java?. For more information, please follow other related articles on the PHP Chinese website!