外部Java文件导入自定义类后无法被主程序编译的问题

我正在开发一个需要编译并执行外部包中Java文件的程序。遇到的问题是：当外部文件导入自定义的Robot类时，主程序无法编译该外部文件；移除该导入语句后，编译可正常进行。

主类代码 #

package zhrfrd.jrobots;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;

public class JRobots {

    public static void main(String[] args) throws IOException {
        // Compile and execute external java program
        try {
            Process processCompilation = Runtime.getRuntime().exec("javac -d /Users/faridzouheir/eclipse-workspace/JRobots/src/ /Users/faridzouheir/eclipse-workspace/JRobots/src/zhrfrd/testjrobots/Test.java");   // Compile Test.java
            processCompilation.waitFor();   // Wait until the process is terminated before starting the following process (to avoid the second process not working properly)
            Process processExecution = Runtime.getRuntime().exec("java -cp /Users/faridzouheir/eclipse-workspace/JRobots/src/ zhrfrd.testjrobots.Test");   // Execute java (-cp is class path)
            
            BufferedReader in = new BufferedReader(new InputStreamReader(processExecution.getInputStream()));   // Get result of the execution of the external file
            String line = null;
            
            while ((line = in.readLine()) != null) { 
                System.out.println(line); 
            }
        } catch (IOException e) {  
            e.printStackTrace();
            System.out.println("Execution error.");
        } catch (InterruptedException e) {
            e.printStackTrace();
            System.out.println("Interrupted exception.");
        }
    }
}

待执行的外部文件（Test）代码 #

package zhrfrd.testjrobots;

import java.io.IOException;

import zhrfrd.jrobots.Robot;   // 就是这个导入语句导致编译失败

public class Test{
    private static final long serialVersionUID = 1L;
    static Robot rob;

    public static void main(String[] args) throws IOException {
         Robot rob;
        int a = 300;
        int b = 23;
        int res = doSum(a, b);
        System.out.println(res);
//         boom();
        rob = new Robot();
        rob.boom();
    }

    public static int doSum(int a, int b) {
        return a + b;
    }
}

Robot类代码 #

package zhrfrd.jrobots;

import java.awt.Dimension;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JLabel;

public class Robot extends JLabel implements Runnable{
    protected static final long serialVersionUID = 1L;
    protected int life, direction, speed, posX, posY;
    protected Thread threadRobot;
    private Random random;
    private Dimension size;

    // Constructor
    public Robot() throws IOException {
        this.life = 100;
        threadRobot = new Thread(this, "My thread");
    }
    
    // Methods
    //Set robot position
    public void setPosition() {
        random = new Random();
        posX = random.nextInt(500);
        posY = random.nextInt(500);
        size = this.getPreferredSize();
        this.setBounds(posX, posY, size.width, size.height);
        
        System.out.println(posX);
    }
    
    //TEST METHOD
    public void boom() {
        System.out.println("BOOM BOOM!!");
    }

    @Override
    public void run () {
        System.out.println(threadRobot.getName());
        setPosition();
        
    }
}

补充说明 #

• 曾尝试将Robot类移至Test所在的同一包中，但问题仍未解决。
• 若移除Test类的main方法并将其改为Robot的子类，是否仍可编译并执行？

1. 修复编译命令的类路径问题 #

你当前的编译命令只传入了Test.java，但编译器找不到依赖的Robot类。需要给javac指定类路径，或者同时编译依赖的源文件：

方式一：指定类路径（适用于Robot已编译的情况）

修改编译命令为：

javac -d /Users/faridzouheir/eclipse-workspace/JRobots/src/ -cp /Users/faridzouheir/eclipse-workspace/JRobots/src/ /Users/faridzouheir/eclipse-workspace/JRobots/src/zhrfrd/testjrobots/Test.java

-cp参数告诉编译器去哪里找Robot类的字节码文件。

方式二：同时编译两个源文件（适用于Robot未编译的情况）

javac -d /Users/faridzouheir/eclipse-workspace/JRobots/src/ /Users/faridzouheir/eclipse-workspace/JRobots/src/zhrfrd/jrobots/Robot.java /Users/faridzouheir/eclipse-workspace/JRobots/src/zhrfrd/testjrobots/Test.java

2. 移包后仍失败的处理 #

把Robot移到Test同包后，先清理src目录下所有旧的.class文件，再重新编译，避免旧字节码导致的路径混淆。

3. 改为Robot子类的可行性 #

完全可以，但需要调整执行逻辑：

• 修改Test类为Robot的子类：

package zhrfrd.testjrobots;

import java.io.IOException;

import zhrfrd.jrobots.Robot;

public class Test extends Robot {
    private static final long serialVersionUID = 1L;

    public Test() throws IOException {
        super();
    }

    public static int doSum(int a, int b) {
        return a + b;
    }
}

• 由于Test类没有main方法，不能直接用java命令执行，需要在JRobots类中通过反射或者直接实例化的方式调用该子类，比如：

// 在JRobots的main方法中，编译后添加以下逻辑
Class<?> testClass = Class.forName("zhrfrd.testjrobots.Test");
Robot testRobot = (Robot) testClass.getConstructor().newInstance();
testRobot.boom();

内容的提问来源于stack exchange，提问作者zhrfrd