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This article introduces the knowledge of "what is a Java memory leak". In the operation of actual cases, many people will encounter such a dilemma. Next, let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Definition of memory leak: objects that the application no longer uses, but the garbage collector cannot delete them because they are being referenced.

To understand this definition, we need to understand the state of the object in memory. The following figure shows what is unreferenced and what is a referenced object.

As can be seen from the figure, there are referenced objects and unreferenced objects. Unreferenced objects will be garbage collected, while referenced objects will not be garbage collected. An unreferenced object must be unused because no other object references it. However, not all unused objects are unreferenced, and some of them are referenced! This is the source of the memory leak.

Why did the memory leak occur?

Let's take a look at the following example to see why a memory leak occurred. In the following example, object A refers to object B. The life cycle of A (T1-T4) is much longer than that of B (T2-T3). When B is no longer used in the application, A still has a reference to B so that the garbage collector cannot delete B from memory. This can lead to out-of-memory problems, because if A does the same thing for more objects at the same time, there will be many objects like B that don't collect and take up memory space.

B may also have a bunch of references to other objects, and the objects referenced by B will not be collected. All these unused objects will consume valuable memory space.

How to prevent memory leaks?

Here are some quick and practical tips for preventing memory leaks.

Pay attention to collection classes, such as HashMap, ArrayList, and so on, as they are common places to find memory leaks. When they are declared static, their lifetime is the same as that of the application.

Pay attention to event listeners and callbacks. If a listener is registered, but a memory leak may occur when the class is no longer in use.

If a class manages its own memory, the program should be wary of memory leaks. In general, member variables pointing to other objects need to be null values.

That's all for "what is a Java memory leak?" Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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