mardi 28 juin 2016

java program doesn't recognizes subordinate classes "package input does not exist"

I'm trying to understand this demonstration example. Only the class HelloWorld is given, therefore I have to implement the Input and the Output class myself.

i understand the error message: java can't find the Input.java and the Output.java file, while importing them. therefore the file HelloWorld.class is not correctly built. But i don't understand the reason why this happens. I guess, I've made a small mistake in the directory structure of the filesystem or the imports - but i can't spot it. Where is my error?

I've read also 2 and 3, but that also doesn't work.


HelloWorld.java

package org.fedoraproject.helloworld;

import org.fedoraproject.helloworld.input.Input;
import org.fedoraproject.helloworld.output.Output;

public class HelloWorld {
    public static void main(String[] args) {
        System.out.print("What is your name?: ");
        String reply = Input.getInput();
        Output.output(reply);
    }
}

Input.java

package org.fedoraproject.helloworld;

import java.util.Scanner;

public class Input {

    public static String getInput() {
        Scanner scanner = new Scanner(System.in);
        String returnVal = scanner.next();
        scanner.close();

        return returnVal;
    }

}

Output.java

package org.fedoraproject.helloworld;

public class Output {

    public static void output(String s) {
        System.out.println(s);

    }
}

$ find
.
./src
./src/org
./src/org/fedoraproject
./src/org/fedoraproject/helloworld
./src/org/fedoraproject/helloworld/output
./src/org/fedoraproject/helloworld/output/Output.class
./src/org/fedoraproject/helloworld/output/Output.java
./src/org/fedoraproject/helloworld/input
./src/org/fedoraproject/helloworld/input/Input.class
./src/org/fedoraproject/helloworld/input/Input.java
./src/org/fedoraproject/helloworld/HelloWorld.class
./src/org/fedoraproject/helloworld/HelloWorld.java

$ java -cp src/org/fedoraproject/helloworld/input/Input.class:src/org/fedoraproject/helloworld/output/Output.class src/org/fedoraproject/helloworld/HelloWorld.class
Error: Could not find or load main class src.org.fedoraproject.helloworld.HelloWorld.class

$ javac -cp src/ src/org/fedoraproject/helloworld/HelloWorld.java
src/org/fedoraproject/helloworld/HelloWorld.java:3: error: cannot access Input
import org.fedoraproject.helloworld.input.Input;
                                         ^
  bad source file: src/org/fedoraproject/helloworld/input/Input.java
    file does not contain class org.fedoraproject.helloworld.input.Input
    Please remove or make sure it appears in the correct subdirectory of the sourcepath.

Update:

After changing the package declarations of Input.java and Output.java to:

package org.fedoraproject.helloworld.input;
package org.fedoraproject.helloworld.output;

which produces (applying the suggestions in the answers):

$ javac -cp src org/fedoraproject/helloworld/HelloWorld.java
org/fedoraproject/helloworld/HelloWorld.java:3: error: package org.fedoraproject.helloworld.input does not exist
import org.fedoraproject.helloworld.input.Input;
                                         ^
org/fedoraproject/helloworld/HelloWorld.java:4: error: package org.fedoraproject.helloworld.output does not exist
import org.fedoraproject.helloworld.output.Output;
                                          ^
org/fedoraproject/helloworld/HelloWorld.java:9: error: cannot find symbol
        String reply = Input.getInput();
                       ^
  symbol:   variable Input
  location: class HelloWorld
org/fedoraproject/helloworld/HelloWorld.java:10: error: cannot find symbol
        Output.output(reply);
        ^
  symbol:   variable Output
  location: class HelloWorld
4 errors

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