编译 java 时找不到符号

Question

I have few classes in the same package demo, but the most important are Server.java and MyServerImpl.java. In Server.java I have this code

package demo;

public class Server
{public static void main( String[] args ) throws Exception
        {
MyServerImpl s = new MyServerImpl("blablabla");
...
}

And the class MyServerImpl

package demo;

public class MyServerImpl extends MyServerPOA {

        private String location;

        public MyServerImpl( String location )
        {
            this.location = location;
        }

        public void add ( String value ){
            System.out.println("name " + value + location );

        }
            }

When I try to compile with javac I have this error

cannot find symbol
symbol  : class MyServerImpl
location: class demo.Server
            MyServerImpl s = new MyServerImpl("blablabla");

I try to compile with this command javac project/demo/Server.java and when I am in the demo folder javac Server.java but still get the same error

Answer 1

To expand on my comment:

When javac looks for classes, the folders it looks in are based off of the fully qualified name for the class.

So in your case, the fully qualified name for MyServerImpl is demo.MyServerImpl . Thus, when the compiler encounters MyServerImpl in Server.java , it looks for a folder called demo , and if it finds that folder, looks for MyServerImpl.java .

If you cd 'd into demo, this will cause compilation to fail, because demo obviously doesn't contain itself (otherwise you might have some broken OSs).

So what you need to do is cd into the folder above demo . So for example, if your file hierarchy is src as root, with the demo package inside, with Server.java and MyServerImpl.java inside:

1. cd into src , so that if you ls / dir , demo is (one of) the folder(s) that shows up
2. javac demo/Server.java
3. Done (hopefully)