running java from command line

Question

I have been mostly using eclipse so far. Now I'm trying to run java from terminal but I have a problem with packages.

This is my Main.java file:

package main;

class Main {
    public static void main(String[] args) {
        System.out.println("it's working");
    }
}

I compile this using javac Main.java and then run with java Main which gives me:

java Main
Exception in thread "main" java.lang.NoClassDefFoundError: Main
Caused by: java.lang.ClassNotFoundException: Main
        at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: Main. Program will exit.

When I remove package Main everything works fine. What am I missing?

java -version gives:

java version "1.6.0_24"
OpenJDK Runtime Environment (IcedTea6 1.11.4) (6b24-1.11.4-1ubuntu0.12.04.1)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)

Your Java source file locations must (a) match their packaging, and (b) must be taken into account when setting the java command's classpath. — Dave Newton
– Dave Newton, Commented Oct 18, 2012 at 22:20
See my answer below, you need to be up in the root directory. Are you running this from within the 'main' directory? — Marplesoft
– Marplesoft, Commented Oct 18, 2012 at 22:21

Brian Roach · Accepted Answer · 2013-12-21 17:56:46Z

6

You need to run the java command up one directory level and give it in the fully qualified package name, eg: java main.Main

See How the Java Launcher Finds User Classes to learn how this works.

edited Dec 21, 2013 at 17:56

Brian Roach

77k12 gold badges140 silver badges164 bronze badges

answered Oct 18, 2012 at 22:20

Marplesoft

6,2904 gold badges40 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Reimeus · Accepted Answer · 2012-10-18 22:18:15Z

0

You can use this command:

java main.Main

Make sure the main (lowercase) package directory is on the classpath.

answered Oct 18, 2012 at 22:18

Reimeus

160k16 gold badges225 silver badges282 bronze badges

Comments

Lews Therin · Accepted Answer · 2012-10-18 22:28:17Z

0

It is possible that your classpath is not set correctly. Since you gave your .java file a package it is unnamed no longer.

An example:

java -cp ./package1/ main.Main //from the current directory and 
                               //if main package is contained in package1

You need to fully qualify the class name. For future reference if you want to run from the command line you must stop the indirection (for lack of a better term) at the package level. Say your class was in the package package1.package2.Main.java I would run it like so java -cp /blah/blah package1.package2.Main

edited Oct 18, 2012 at 22:28

answered Oct 18, 2012 at 22:19

Lews Therin

11k4 gold badges51 silver badges72 bronze badges

Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Compile

Windows:
javac main\Main.java
Mac:
javac main/Main.java

Run

java main.Main

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Oct 19, 2012 at 2:31

Mordechai

16.5k2 gold badges51 silver badges89 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 12:27:56Z

0

If you add package Main, then you must put your source file in folder Main/Main.java. After that you can compile. When you run the program, go to Main folder using "cd", then write java -cp Main.Main See my question similiar to yours noclassdeffounderror

edited May 23, 2017 at 12:27

CommunityBot

11 silver badge

answered Oct 19, 2012 at 3:47

Tao Huang

1,3411 gold badge12 silver badges15 bronze badges

Comments

raj · Accepted Answer · 2012-10-19 10:54:00Z

0

try this...

In window , you just compile the code as

javac - d . Main.java

then a package(folder) with the name you specified in your class is created (in your code, package with name "main" is created) in the same path where your program reside...

Then you just run the program as java main.Main or java main/Main

answered Oct 19, 2012 at 10:54

raj

3852 silver badges10 bronze badges

Collectives™ on Stack Overflow

running java from command line

6 Answers 6

Comments

Comments

Comments

Compile

Run

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

Comments

Comments

Comments

Compile

Run

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related