Java如何修改.class文件变量

/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/9/5 11:18
 * @history: 1.2020/9/5 created by wei.wang
 */
public class HelloWorld {
  public static void main(String[] args) {
    String word = "Hello World";
    System.out.println(word);
  }
}

/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/9/4 19:42
 * @history: 1.2020/9/4 created by wei.wang
 */

import java.io.*;

import org.gjt.jclasslib.io.ClassFileWriter;
import org.gjt.jclasslib.structures.CPInfo;
import org.gjt.jclasslib.structures.ClassFile;
import org.gjt.jclasslib.structures.constants.ConstantUtf8Info;

public class Test {
  public static void main(String[] args) throws Exception {

    String filePath = "F:\\GitCode\\zero\\test111\\target\\classes\\HelloWorld.class";
    FileInputStream fis = new FileInputStream(filePath);

    DataInput di = new DataInputStream(fis);
    ClassFile cf = new ClassFile();
    cf.read(di);

    CPInfo[] infos = cf.getConstantPool();

    int count = infos.length;
    System.out.println(count);

    for (int i = 0; i < count; i++) {
      if (infos[i] != null) {
        System.out.print(i);
        System.out.print(" = ");
        System.out.print(infos[i].getVerbose());
        System.out.print(" = ");
        System.out.println(infos[i].getTagVerbose());
        //对23进行修改
        if(i == 23){
          ConstantUtf8Info uInfo = (ConstantUtf8Info)infos[i];
          uInfo.setBytes("Hello World HELLO WORLD".getBytes());
          infos[i]=uInfo;
        }
      }
    }

    cf.setConstantPool(infos);
    fis.close();
    File f = new File(filePath);
    ClassFileWriter.writeToFile(f, cf);
  }
}

public class HelloWorld {
  public HelloWorld() {
  }

  public static void main(String[] args) {
    String word = "Hello World HELLO WORLD";
    System.out.println(word);
  }
}