Detailed explanation of how to use IntelliJ IDEA for Java memory analysis

Preface

In Java development, memory management is a very important topic. Problems such as memory leaks, excessive use of memory, off-heap memory often affect the performance and stability of the application. Fortunately,IntelliJ IDEAProvides some powerful tools to help developers analyze and optimize the memory usage of Java applications.

In this article, we will explore in-depth how to use itIntelliJ IDEACarry out memory analysis of Java applications. We will learn how to use the tools provided by IDEA for memory analysis, including viewing memory consumption, analyzing memory leaks, garbage collection, etc.

1. Preparation

1.1 IntelliJ IDEA Configuration

In order to be able to use IntelliJ IDEA for memory analysis, you first need to make sure that you have installed the relevant plug-ins in IntelliJ IDEA and that your project is configured correctly. Here are the preparations to be done:

Install the JVM Profiler plugin：
- Open IntelliJ IDEA.
- ClickFile > Settings > Plugins。
- Search in the plugin search boxJVM ProfilerPlugin and install.
Enable JVM Analytics Tools：
- After opening the project, make sure the project runs correctly.
- ConfigurationJVM parameters, for example, you can use-XmxTo increase the maximum heap memory size, ensure that your application can run under memory pressure so that it can analyze memory problems.

2. Basic concepts of memory analysis

Before performing memory analysis, it is very necessary to understand the following important concepts:

Heap：
- The heap is the area used by the JVM to dynamically allocate memory. Java objects all allocate memory on the heap.
Non-Heap Memory (Non-Heap)：
- Non-heap memory mainly includes method area (Method Area), Class information inside the JVM, etc. It is usually used to store class information and constant pools, etc.
Garbage Collect (GC)：
- Garbage collection is an important mechanism for JVM to manage memory, which is used to automatically recycle memory occupied by objects that are no longer used.
Stack and memory leaks：
- Stack: Local variables and method call stacks are stored in the stack area.
- Memory leak: Objects are no longer used, but because some references are not cleared, the garbage collector cannot recycle, resulting in excessive memory usage.

3. Use IntelliJ IDEA for Java memory analysis

3.1 Check JVM memory usage

IntelliJ IDEA provides a visualization tool to help you view the memory usage of your application.

Start the memory analyzer：
- In IntelliJ IDEA, open your project and launch the app.
- existRunSelect from the menuEdit Configurationsand select the run configuration you want to analyze.
- On the settings page of the run configuration, findVM optionsInput box, where you can set JVM parameters, for example:
```
-Xms512m -Xmx2048m
```
  This will set the initial heap memory to 512MB for the application and the maximum heap memory to 2GB.
Start the memory analysis tool：
- In the project's running interface, clickRun > Profiler。
- This will start aCPUandMemory Profiler, you can monitor the allocation and usage of memory in real time.
Analyze memory usage：
- existMemory ProfilerIn , you can see changes in heap memory, tracking object allocation, and garbage collection process.

3.2 Using JVM Profiler for memory analysis

passJVM ProfilerPlugins, you can have a deeper understanding of the memory usage of your application. The following steps can be performed:

Start JVM Profiler：
- In IntelliJ IDEA, launch your app.
- existRunSelect from the menuJVM Profiler, and then clickMemoryTags to view memory allocation.
Check memory allocation：
- Memory ProfilerProvides a chart of memory usage, including the allocation of heap memory, the allocation of various objects, garbage collection (GC) and other information.
- You can find possible memory problems by viewing real-time graphical changes in memory.
Track object assignment：
- In the memory analyzer, you can clickHeap DumpButton, take a snapshot of the application memory.
- Through object snapshots, you can view the objects that survive in the heap and analyze which objects occupy too much memory.

3.3 Analyze garbage collection

Garbage collection is a core part of JVM memory management, and analyzing garbage collection can help you discover memory leaks or excessive GC pause time.

View GC logs：
- When starting the JVM, you can enable GC logs:
```
-Xlog:gc*:file=
```
  This will record the relevant information of garbage collection toin the file. The log allows you to view the time, type and pause time of each garbage collection.
Garbage recycling analysis：
- existJVM Profiler, you can view the details of garbage collection, including:
  - Garbage recycling pause time at each stage.
  - Allocation and recycling of heap memory.
  - Long-term Full GC and Minor GC.
Through this information, you can find whether there are frequent garbage collection issues, or whether there are objects that cannot be recycled due to memory leaks.

3.4 Heap analysis and memory leak detection

Memory leaks are a common memory problem that occurs when objects are not properly released, causing memory to continue to increase. Using IntelliJ IDEA can help you detect this problem.

Perform Heap Dump：
- In the memory analysis tool, you can generate a heap dump (Heap Dump). With heap dump, you can see which objects occupy too much memory, or even objects that cannot be recycled.
```
public class TestMemoryLeak {
    private static List&lt;Object&gt; list = new ArrayList&lt;&gt;();

    public static void main(String[] args) {
        while (true) {
            (new byte[1024 * 1024]); // Add 1MB of data per second        }
    }
}
```
The above code simulates a memory leak, and new memory is allocated every time the loop, but it is not released. In practical application,Heap Dumpcan help discover this situation.
Heap Dump：
- existHeap DumpIn the view, you can view all objects in the heap and analyze memory leaks through class names, sizes and other information.
- Check the number and size of the instances to determine whether objects are piled in memory and not garbage collected.
Use Memory Profiler to view leaks：
- start upMemory ProfilerAfter that, check the number of instances for each class to change. If the number of instances of certain classes continues to grow and are not recycled in time, it may be a sign of a memory leak.

4. Practical case: Analyzing a memory leak problem

Suppose you encounter a Java application that has a memory leak problem. Use IntelliJ IDEA to diagnose and repair.

Code example:

import ;
import ;

public class MemoryLeakTest {
    private List&lt;byte[]&gt; list = new ArrayList&lt;&gt;();

    public void createMemoryLeak() {
        while (true) {
            (new byte[1024 * 1024 * 10]); // Add 10MB of object each time        }
    }

    public static void main(String[] args) {
        MemoryLeakTest test = new MemoryLeakTest();
        ();
    }
}

Using IntelliJ IDEA Analysis：
- Launch the application and monitor its memory usage.
- GenerateHeap Dump,CheckArrayListand the one in itbyte[]Objects occupy a lot of memory.
- Check whether the object has been recycled and confirm that it cannot be recycled by GC.
Solution：
- Avoid unlimited memory allocation and use appropriate caching mechanisms.
- Regularly clean objects that are no longer used, or use soft references or weak references to avoid memory leakage.

5. Summary

Through this article, you have learned how to use itIntelliJ IDEACarry out Java memory analysis. Mastered the following skills:

useJVM ProfilerCheck memory usage.
useHeap DumpDiagnose memory leaks.
Analyze the garbage collection situation and optimize performance.

IntelliJ IDEA

The memory analysis tool is very powerful and can help developers quickly locate memory problems and improve application performance and stability. I hope that through this article, you can better understand and use IDEA's memory analysis tools, thereby improving development efficiency.

This is the end of this article about how to use IntelliJ IDEA for Java memory analysis. For more related IDEA Java memory analysis content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!