如何在Java中正确导入类？

Question

I am running into following errors while trying to compile a java program on ubbuntu 12.04. . For ease of usage I have put all the classes in the same directory as the java program. I will provide the error message, the main java program as well as the class listing. I deleted the first few comment lines hence the line numbers of the error mesage do not match. I am having problem with the import statements "Scoring Request" and "ScoringResponse"

Also here is the env output

JAVA_HOME=/usr/local/java/jdk1.7.0_10

CLASSPATH=:/home/syedk/WEKA/weka-3-7-9/mysql-connector-java-3.1.17-bin.jar

Error message 
=============
javac Scoring.java


Scoring.java:37: error: '.' expected
import ScoringRequest;
                     ^
Scoring.java:37: error: ';' expected
import ScoringRequest;
                      ^
Scoring.java:38: error: class, interface, or enum expected
import ScoringResponse;
       ^

3 errors

package Scoring;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import ScoringRequest;
import ScoringResponse;

@WebServlet( name="Scoring", displayName="Scoring Servlet", urlPatterns = {"/Scoring"}, loadOnStartup=1)
public class Scoring extends HttpServlet {

    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        BufferedReader reader = null;
        BufferedWriter writer = null;
        ScoringRequest req = null;

        try {
            reader = new BufferedReader(new InputStreamReader(
                    request.getInputStream()));

            StringBuffer xml = new StringBuffer();
            String line = reader.readLine();
            while (line != null) {
                xml.append(line);
                line = reader.readLine();
            }

            req = new ScoringRequest(xml.toString(), null, null,
                    null);

            ScoringResponse res = (new ScoringEngine()).score(req);

            writer = new BufferedWriter(new OutputStreamWriter(
                    response.getOutputStream()));
            writer.write(res.toXML());
            writer.flush();

        } catch (Exception ex) {
            System.err.println(ex);

            ScoringResponse res = new ScoringResponse(req.getModelName(), req.getPmmlURL(), req.getCsvInputRows(), null);
            StringWriter errWriter = new StringWriter();
            ex.printStackTrace(new PrintWriter(errWriter));
            res.setErrorMessage(errWriter.toString());
//          res.setErrorMessage(ex.getMessage());

            writer = new BufferedWriter(new OutputStreamWriter(
                    response.getOutputStream()));
            writer.write(res.toXML());
            writer.flush();

        } finally {
            try {
                if (reader != null)
                    reader.close();
            } catch (Exception ex) {
            }

            try {
                if (writer != null)
                    writer.close();
            } catch (Exception ex) {
            }

        }
    }
}

Answer 1

These are the problem:

import ScoringRequest;
import ScoringResponse;

You don't import classes from the default package - they're just accessible already. Just remove these two lines and it should be fine - or better, move them into a named package and import them from there. Of course you don't need to import them at all if they're in the same package as the code you're importing in.

As a side note, I would strongly recommend against naming a package the same as a class, as you are doing here:

package Scoring;

...

public class Scoring extends HttpServlet {
    ...
}

Aside from anything else, Scoring violated the Java conventions for package names.