读取CLASS文件JDK版本

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读取CLASS文件JDK版本

package com.tool.classversion;import java.io.FileInputStream;/* * (magic):0xCAFEBABE// 5.0// (version):49.0// 6.0// (version):50.0// 1.4// (version):46.0// 1.3// (version):45.3 * */public class JavaVersionUtil {public static void main(String args[]) {String fileName = "PolicyInterfaceReqModel.class";printVersion(fileName);}public static void printVersion(String fileName) {try {FileInputStream fis = new FileInputStream(fileName);byte[] data = new byte[8];fis.read(data);fis.close();parseFile(data);} catch (Exception e) {System.out.println(e);}}private static void parseFile(byte[] data) {System.out.print("(magic):0x");System.out.print(Integer.toHexString(data[0]).substring(6).toUpperCase());System.out.print(Integer.toHexString(data[1]).substring(6).toUpperCase());System.out.print(Integer.toHexString(data[2]).substring(6).toUpperCase());System.out.println(Integer.toHexString(data[3]).substring(6).toUpperCase());int minor_version = (((int) data[4]) << 8) + data[5];int major_version = (((int) data[6]) << 8) + data[7];System.out.println("(version):" + major_version + "."+ minor_version);}}