java -查看编译当前class的JDK版本

package cn.com.jit.pki.koaltoolkit.impl;

import java.io.DataInputStream;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

public class Test {

 private static final int JAVA_CLASS_MAGIC = 0xCAFEBABE;

 public static void main(String[] args) {

  

  //CertApplyDataConvertImpl  cm=new CertApplyDataConvertImpl();

     try {               

         DataInputStream dis = new DataInputStream(new FileInputStream("C:\\Users\\Administrator\\Desktop\\SJY42ForSPKM.class"));

         int magic = dis.readInt();

         if(magic == JAVA_CLASS_MAGIC){

          int minorVersion = dis.readUnsignedShort();

          int majorVersion = dis.readUnsignedShort();

         

//          Java 1.2 uses major version 46

//          Java 1.3 uses major version 47

//          Java 1.4 uses major version 48

//          Java 5 uses major version 49

//          Java 6 uses major version 50

//          Java 7 uses major version 51  

         

          System.out.println("ClassVersionTest.main() " + majorVersion + "." + minorVersion);

          }

          }catch (FileNotFoundException e){

           // TODO Auto-generated catch block

            e.printStackTrace();

           } catch (IOException e){

           // TODO Auto-generated catch block

            e.printStackTrace();

           }

       }

}