Run from command line, Wrong Name error

Question

I want to run a Java project from the command line which I start using a batch file, but I get the wrong name error.

The directory setup:

• srcMVC
  • bin (folder with .class files)
  • src (folder with .java files)
  • Batch file

Batch file:

set path=C:\Program Files\Java\jdk1.7.0_09\bin
javac src\model\*.java -d bin -cp src
javac src\controller\*.java -d bin -cp src
javac src\view\*.java -d bin -cp src
javac src\main\*.java -d bin -cp src
PAUSE
java bin\main.Main
PAUSE

Compiling works, but I get the following error:

Exception in thread "main" java.lang.NoClassDefFoundError: bin\main/Main (wrong name: main/Main)             

Any suggestions?

---

package main;

// omitted imports

public class Main {
    // omitted variables

    public static void main(String[] args) {
        // omitted implementation   
    }
}

Answer 1

The following statement resolved my error:

java -cp bin; main.Main

Answer 2

NoClassDefFoundError in Java comes when Java Virtual Machine is not able to find a particular class at runtime which was available during compile time.

For example if we have a method call from a class or accessing any static member of a Class and that class is not available during run-time then JVM will throw NoClassDefFoundError.

By default Java CLASSPATH points to current directory denoted by "." and it will look for any class only in current directory.

So, You need to add other paths to CLASSPATH at run time. Read more Setting the classpath

java -cp bin main.Main

where Main.class contains public static void main(String []arg)

Answer 3

Java run time (in your case the java.exe command), takes the class file name that containst the main() method as input. I guess you should be invoking it as "java bin\main" assuming there is a main.class which has a public static void main (String[]) method defined.

Note: General practice is to capitalize the first literal of any class name.

Answer 4

java bin/main.Main is wrong, you must specify -cp here:

java main.Main -cp bin

Here the first argument is the class name which should be found in the classpaths, rather than the class file location. And -cp just adds the logical path to classpaths. You should make the root of your project searchable in the classpath.

and for those javac commands, you have already specified the correct path, so you don't need -cp src. The difference here is the javac command uses logical path for .java files, while using java command you could only specify the path in -cp attribute.

You could also execute java main.Main without -cp if you enter the directory bin:

cd bin
java main.Main

Since the current path will be automatically be searched by java as a classpath.

Answer 5

Assuming you have a class called Main you have to run it with this command:

java bin\Main

It will call your main method.

Answer 6

you are wrongly exicuting java bin\main.main

main() is your main method but you should supply java interpreter the Class Name which implements main()

So if your class name is Test and file name is Test.java which has main() method

java Test

if your Test.java/Test class in is package my.test e.g - package com.my.test;

than, java com.my.test.Test

hope you got it !!