public class VersionDemo {    public static void main(String args[]) {     System.out.println( "java 版本：\t" + System.getProperty( "java.version"));     System.out.println( "jvm 实现版本：\t"         + System.getProperty( "java.vm.version"));     System.out.println( "jvm 规范版本：\t"         + System.getProperty( "java.vm.specification.version"));   } }