CODEWITHSUNDEEP
javapackage
dirascorpio
dirascorpio

Reputation: 31

Packages in Java

It's my first time using packages in Java, and I'm not sure where I went wrong. I'm trying to make a Tetris game. Here's part of my code:

package mytetris;

import javax.swing.*;
import java.awt.*;

public class Tetris extends JFrame {

    // class constructor
    public Tetris() {
        super("Tetris");
        this.setSize(400, 600);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);

        // just started, haven't really done anything

        this.setVisible(true);
    }

    public static void main(String[] args) {
        Tetris myTetris = new Tetris();
    }
}

I then compiled it using javac Tetris.java and then I tried running it using java Tetris, this is what the terminal gave me:

Exception in thread "main" java.lang.NoClassDefFoundError: Tetris (wrong name: mytetris/Tetris)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Upvotes: 2

Views: 2166

Answers (6)

Priyadharshan Vikram
Priyadharshan Vikram

Reputation: 11

This error is because the class mentioned in your program is not fount by JVM in the class loader. There are various reasons for this error. check the detailed concept here https://te-xplore-ch.blogspot.com/2020/08/java-architecture.html May be your package was not added in the source folder. Click build path for the folder and click use as a source folder

Upvotes: 0

A L K
A L K

Reputation: 1

If you observe compilation code by the command javap your class name i.e

javap Tetris then it display it as 

class mytetris.Tetris{

}

So when you execute this program ,you have to give command like this.

java mytetris.Tetris then your program executes smoothly.

Upvotes: 0

lindenrovio
lindenrovio

Reputation: 357

Suppose you have your file in /home/mytetris/Tetris.java

Then you need to run "java mytetris.Tetris" in the directory home.

Because you specified package mytetris, it will go to find your files in the directory mytetris, where it will find the class Tetris.

Upvotes: 3

ako
ako

Reputation: 420

Assuming that you have the following project structure:

project/src/mytetris/Tetris.java
project/classes

Run from the project dir:

javac src/mytetris/Tetris.java -d classes

It will compile Tetris.java and put it into classes dir.

Upvotes: 0

emory
emory

Reputation: 10891

I think you should call it as

java mytetris.Tetris

Upvotes: 1

venergiac
venergiac

Reputation: 7697

try

java mytetris.Tetris

use fully qualified class name

Upvotes: 0

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