main class could not be found or loaded even tough there is a main method

Question

I have two classes ChatClient and Listener and want to comile and run them. In eclipse it works fine, but on terminal I can't get it run. Both classes are on the path: /Desktop/java/task4. Maybe I should mention that inside the ChatClient class a Listener Object gets created.

I compile the two classes with the command: javac *.java and get 2 classes created. But if I type java ChatClient I get the error main class could not be found or loaded. What am I doing wrong? I'm using Ubuntu. And yes there is a main method inside ChatClient

public class Listen extends Thread {
Socket s;
Scanner msg;

public Listen(Socket s) {
    ....

}

public class Chatter {


public static void main(String[] args) {
    try {
        ...
        Listener lt = new Listener(s);
        ...
}

Could you provide some extra information like; classes and commands you use when tried to compile? — Ekrem Demirhan, May 04 '19 at 11:02
posted my code. @EkremDemirhan I Don't know what you mean by commands. First I type 'javac *.java' and get the classes and then I type 'java ChatClient' and get the error on the title — quinzo, May 04 '19 at 11:09
@quinzo I mean if there was no problem when running on Eclipse, it can be caused by the commands you use. — Ekrem Demirhan, May 04 '19 at 11:16
the path `/Desktop/java/task4` alone is nothing special; what is the class path, which is the directory you are running the `java` command in, what are the packages (if any), what is the complete error message — user85421, May 04 '19 at 11:21
`java UE3.ChatClient`, both classes must be in a directory `UE3` and the parent directory of `UE3` must be on the class path (or, when using default, the java command must be called in that parent directory) — user85421, May 04 '19 at 11:22
I created a package with eclipse, but I'm not sure if I have to do something extra if I compile& run it on terminal — quinzo, May 04 '19 at 11:23
Tutorial: [Managing Source and Class Files](https://docs.oracle.com/javase/tutorial/java/package/managingfiles.html) may help — user85421, May 04 '19 at 11:27
@CarlosHeuberger exact error message: Error: Could not find or load main class UE3.ChatClient — quinzo, May 04 '19 at 11:35
you are 2 comments late... my (that) question was for **before** you edited — user85421, May 04 '19 at 11:38
This link https://stackoverflow.com/questions/18093928/what-does-could-not-find-or-load-main-class-mean will be helpful. — Suseendran P, May 04 '19 at 11:55

score 0 · Answer 1 · answered May 04 '19 at 11:30

There are many possibilities are there to get this error, while running from cmd. Because IDE will do many things related to class path in back ground.

Highest possibility of getting this error is, beginners will not aware of giving the full package structure while running using `java cmd` from correct classpath directory. Please go to this link for more information.

score 0 · Answer 2 · answered May 04 '19 at 12:13

The obvious problem is that you class is in a package (UE3) but you have not used the full qualified class name. Try:

java UE3.ChatClient

There are many other possible problems, such as the classpath not being setup correctly.

(Note the convention for package names is all lowercase. Also rather than extending Thread you should typically pass in a Runnable as a lambda or method reference.)

main class could not be found or loaded even tough there is a main method

2 Answers2