Java jar： A JNI error has occurred, please check your installation and try again

java -verion 和 javac -version 版本不一致

E: empeclipseWorkSpace>java -jar TASTS.jar
Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/swt/widgets/Decorations
Caused by: java.lang.ClassNotFoundException: org.eclipse.swt.widgets.Decorations
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: MainForm. Program will exit.

E: empeclipseWorkSpace>

 E: empeclipseWorkSpace>java -jar tasts.jar
Error: A JNI error has occurred, please check your installation and try again （java 版本不一致）
Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/swt/widgets/Decorations
        at java.lang.Class.getDeclaredMethods0(Native Method)
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
        at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
        at java.lang.Class.getMethod0(Class.java:3018)
        at java.lang.Class.getMethod(Class.java:1784)
        at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: org.eclipse.swt.widgets.Decorations
        at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 7 more

E: empeclipseWorkSpace>

E: empeclipseWorkSpace>java -jar tasts.jar
no main manifest attribute, in tasts.jar
在 cmd 下执行 java -jar xxx.jar 包名.类名

报错：

no main manifest attribute, in xxx.jar

产生原因：

一般情况下，java 打包成 jar 包需要在  MANIFEST.MF 中指定 Main-Class 项，以便运行 java -jar xxx.jar 时找到对应的主类。因为-jar的含义就是后面跟的jar包是有main class可独立运行，所以需要在打包成jar包时指定这个类；否则，需要在执行的时候手动指定。

解决方案：

在运行jar包时，使用 -cp / --classpath 来手动指定。

eg：java -cp xxx.jar com.fresher.xxx.类