java - Javac “cannot find symbol”

我有这样的根目录:

├── classes
└── src
    └── vehicles
        ├── Bicycle.java
        └── BicycleMain.java

Bicycle.java

package vehicles;

public class Bicycle {

  public int cadence;
  public int gear;
  public int speed;

  public Bicycle(int startCadence, int startSpeed, int startGear) {
    gear = startGear;
    cadence = startCadence;
    speed = startSpeed;
  }

  public void setCadence(int newValue) {
      cadence = newValue;
  }
  public void setGear(int newValue) {
    gear = newValue;
  }
  public void setSpeed(int newValue) {
    speed = newValue;
  }
  public int getGear() {
    return gear;
  }
  public int getCadence() {
    return cadence;
  }
  public int getSpeed() {
    return speed;
  }
  public void applyBrake(int decrement) {
    speed -= decrement;
  }
  public void speedUp(int increment) {
    speed += increment;
  }

BicycleMain.java

package vehicles; import vehicles.*;

public class BicycleMain {
        public static void main (String args[]){
        Bicycle Bike = new Bicycle(10, 20, 1);
        System.out.println("We have a new bicycle with speed = " +Bike.getSpeed()+", cadence = "+Bike.getCadence()+", gear = "+Bike.getGear());
        } }

我编译了Bicycle.java并成功，但没有为BicycleMain.java进行编译:

symbol  : class Bicycle
location: class vehicles.BicycleMain
    Bicycle Bike = new Bicycle(10, 20, 1);
    ^
src/vehicles/BicycleMain.java:6: cannot find symbol
symbol  : class Bicycle
location: class vehicles.BicycleMain
    Bicycle Bike = new Bicycle(10, 20, 1);
                       ^
2 errors

我尝试使用Netbeans和IT WORKS运行这些文件!但是为什么在CLI中编译时它不起作用？

最佳答案

首先，要使用javac编译Java源文件，您需要指定要显式编译的文件。
例:

javac PathToSourceFile/FileName.java

如果源文件位于当前工作目录中，则无需提供path。
其次，每当Java遇到import abc.xyz.ClassName;时，它都会尝试针对abc/xyz/ClassName或当前工作目录来解析classpath。
因此，如果您位于Vehicles文件夹中并编译代码，则它不会编译，因为它将在文件夹Vehicles中查找文件夹车辆(不存在!)。
但是，您可以在Vehicles文件夹中执行此操作

javac -cp ../ BicycleMain.java

并且应该编译，因为classpath将设置为包含载具的目录(../)。这将解决您的Bicycle类。
然后使用java -cp ../ vehicles/BicycleMain运行。

关于java - Javac “cannot find symbol”，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13537668/