Idea2021 failed to start. Could not find main class com/intellij/idea/main

Catalog

environmental information ：

Problem description ：

cause ：

operation ：

Solution ：

The search results ：

Solutions ：

resolvent ：

Conclusion ：

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environmental information ：

idea2021.1.1（ notes ： If it's another version idea, This problem may also occur ）

jdk1.8、jdk11

Problem description ：

cause ：

because idea It takes a long time to start the project ,5 About minutes , So Baidu idea Occupy cpu And high memory , I found that there was an article that said to change idea Of Runtime Version,

such as ：  Thorough solution Idea Memory consumption is serious and CPU The proportion of resources is serious (baidu.com)

intellij idea cpu The occupancy rate is too large and too full Running too slow Five solutions were finally successful _trusause The blog of -CSDN Blog _idea Too much memory

operation ：

Choose Runtime, From the default sdk11 Change to sdk8,idea The automatic restart failed , Tips ：

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Error launching IDEA
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Could not find main class com/intellij/idea/Main

Solution ：

The search results ：

Search for this error , The solutions given in domestic articles are mostly configuration jdk The path of , Such as  IDEA Initiate error reporting could not find main class com/intellij/idea/main terms of settlement _ Life is like a play All by acting -CSDN Blog

Configure... In environment variables IDEA_JDK_64 wait .

Solutions ：

The idea is actually right , Just can't find the start idea When setting jdk Where the path .

idea Provides a way to start from the command line , stay idea Under the installation path of bin Catalog （ and idea64.exe Same path ） There is one idea.bat Batch file , use cmd or PowerShell Execute this bat after , You can see the details of startup , With PowerShell For example ：

PS C:\Users\xxx> cd D:\develop\IDEA\bin
PS D:\develop\IDEA\bin> .\idea.bat
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: com/intellij/idea/Main has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:495)
PS D:\develop\IDEA\bin>

Reporting a mistake means com.intellij.idea.Main This class file The version number is 55.0（ Corresponding jdk11）, For operation jre yes 52.0（ Corresponding jdk8）.

For correspondence, please refer to another article of mine JDK version and class file version(Class Build number ) Corresponding relation _lzhfdxhxm The blog of -CSDN Blog

Look at the idea.bat The batch , Sort out the process , You can find the used jre Yes, there is Priority judgment Of . There are comments in the batch ：

:: ---------------------------------------------------------------------
:: Locate a JRE installation directory which will be used to run the IDE.
:: Try (in order): IDEA_JDK, idea%BITS%.exe.jdk, ..\jbr[-x86], JDK_HOME, JAVA_HOME.
:: ---------------------------------------------------------------------

IDEA_JDK This environment variable is not configured in my environment variable ;

idea%BITS%.exe.jdk This is not an environment variable , Is the file with the specified path . This file was just installed sdk8 It's automatically generated when / Modified , Here's the picture ：

idea64.exe.jdk The content of the document ：

C:\Users\lzhf\AppData\Roaming\JetBrains\IntelliJIdea2021.1\jdks\jbsdk8u112b287.2_windows_x64

This path is just installed jre8

resolvent ：

Then the solution is simple , Delete idea64.exe.jdk This file Just fine , This will determine the subsequent settings （ This is equivalent to Choose Runtime There is no default sdk11 Change to sdk8）.

If you haven't changed other settings , Then the last used jre yes idea Under the installation path jre：

D:\develop\IDEA\jbr\bin\java.exe

That's it ,idea It started successfully ！

If there are other personalized configurations , Then according to the idea.bat The logic in is sorted out layer by layer , You can always find your own configuration , And fix it . In the process , You can print logs , To aid judgment .

For example, when printing jre The final value ：

Conclusion ：

What this blog post solves is idea because jdk The problem of configuration startup failure .

idea2021 Should not directly support jdk8, Because the startup class com/intellij/idea/Main Yes, it is jdk11 Compilation of , Unless you change the startup class to use jdk8 Just compile .