尝试在 cmd 中运行可执行文件 Jar 时出错

Question

I know there are a few other similar questions to this, but the solutions don't seem to work. (I have read about a dozen stack-overflow forums)

Here is that I tried doing in CMD:

C:\Users\warre>java -jar C:\Users\warre\OneDrive\Desktop\MirrorUserInput.jar
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: usefulTools/Main has been compiled by a more recent version of the Java Runtime (class file version 57.0), 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(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

C:\Users\warre>javac -version
javac 14

C:\Users\warre>java -version
java version "1.8.0_251"
Java(TM) SE Runtime Environment (build 1.8.0_251-b08)
Java HotSpot(TM) Client VM (build 25.251-b08, mixed mode, sharing)

Here is my source code.

I understand that some of the issues may arise from the discrepancy between JDK and JRE but I got confused when I tried to understand that complexity (I know the general difference between the two, and have read a few articles, but get confused exactly why it is causing an issue in eclipse.)

I used eclipse to export this. I used all the default settings. I can send screenshots of this information if requested.

Answer 1

You are right. The discrepancy occurs when version of JDK is higher than the JRE version.

The reported major numbers are:

Java SE 14 = 58,
Java SE 13 = 57,
Java SE 12 = 56,
Java SE 11 = 55,
Java SE 10 = 54,
Java SE 9 = 53,
Java SE 8 = 52,
Java SE 7 = 51,
Java SE 6.0 = 50,
Java SE 5.0 = 49,
JDK 1.4 = 48,
JDK 1.3 = 47,
JDK 1.2 = 46,
JDK 1.1 = 45

Based on the error message I can say for sure that your eclipse JDK version is set as Java 13 and the JRE version of your machine is 8.

You have two solutions. One solution maybe to upgrade your JRE to 13 at least. Or go to the eclipse Java compiler option and decrease the JDK version to JDK 8.

In Eclipse, go to menu command Window -> Preferences -> Java -> Compiler and then set "Compiler compliance level" to 1.8.