识别jar的编译JDK版本

import java.io.InputStream;
import java.io.PrintWriter;public class CMD命令 {
public static void main(String[] args) {
String filePath = "D:/git/new_baiwang/sdk-java/sdk-java/target/classes/com/baiwang/bop/Constants.class";
docmd(filePath);
} static void docmd(String filePath) {
String[] command = { "cmd", };
Process p = null;
try {
p = Runtime.getRuntime().exec(command);
new Thread(new SyncPipe(p.getInputStream())).start();
new Thread(new SyncPipe(p.getErrorStream())).start();
PrintWriter stdin = new PrintWriter(p.getOutputStream());
String ml = "javap -verbose " + filePath;
stdin.println(ml);
stdin.close();
} catch (Exception e) {
throw new RuntimeException("编译出现错误：" + e.getMessage());
}
}
}class SyncPipe implements Runnable { private final InputStream istrm_; public SyncPipe(InputStream istrm) {
istrm_ = istrm;
} public void run() {
try {
final byte[] buffer = new byte[10240];
StringBuffer sbf = new StringBuffer();
for (int length = 0; (length = istrm_.read(buffer)) != -1;) {
sbf.append(new String(buffer, 0, length));
}
String msg = sbf.toString();
if (msg.length() > 10) {
if (msg.contains("major version: 50")) {
System.out.println("编译的JDK版本是1.6");
} else if (msg.contains("major version: 51")) {
System.out.println("编译的JDK版本是1.7");
} else if (msg.contains("major version: 52")) {
System.out.println("编译的JDK版本是1.8");
} else {
System.err.println("运行错误，未知版本！");
System.out.println(msg);
} } else {
System.err.println("运行错误，没有想要的信息！");
}
} catch (Exception e) {
throw new RuntimeException("处理命令出现错误：" + e.getMessage());
}
}
}