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class file contains wrong class error while accessing jar file

I am trying to create a JAR file for my two source codes Serial.java and DBaccess.java.
I am doing this as a learning exercise ,the classes do not do anything,they are dummy classes.
OS - Windows 10
JDK - GraalVM
Listing of my source code.(Serial.java)
public class Serial
{
void open()
{
System.out.println("Serial Port Opened - 0");
}
}
Listing of my source code.(DBaccess.java)
public class DBaccess
{
String DBname = "MySerialDB";
void write()
{
System.out.println("Data Written to DB - W");
}
void read()
{
System.out.println("Data Read from DB - R");
}
}
I have compiled them to .class files using javac
javac DBaccess.java
javac Serial.java
I created a folder
H:\myclass\com\mydomain\util
and manually copied the class files to util directory
and created a jar file myjar.jar of this format
H:\myclass>H:\graalvm\bin\jar tf myjar.jar
META-INF/
META-INF/MANIFEST.MF
com/
com/mydomain/
com/mydomain/util/
com/mydomain/util/DBaccess.class
com/mydomain/util/Serial.class
I want my source code JMainEntry.java to access the classes in the above jar file myjar.jar.
JMainEntry.java
//Main Class of the Program
import com.mydomain.util.*;
public class JMainEntry
{
public static void main (String[] Args)
{
Serial myS = new Serial();
myS.open();
DBaccess myDB = new DBaccess();
myDB.write();
myDB.read();
}
}
When i compile the code
H:\jar-compile>H:\graalvm\bin\javac -cp myjar.jar JMainEntry.java
I am getting the error
bad class file: myjar.jar(/com/mydomain/util/Serial.class)
class file contains wrong class: Serial
Please remove or make sure it appears in the correct subdirectory of the classpath.
I am not able to understand why javac is complaining like this,Can anyone help?

bad class file: myjar.jar(/com/mydomain/util/Serial.class)
Make sure you declare
package com.mydomain.util
at the top of all .java files in the directory com/mydomain/util, including Serial.java. To understand this better, read about packages.

javac throw package doesn't exist but intellij can compile and run

I have a following directory structure:
-com
-laicode
-class1
-QuickSort.java
-common
-someclasses
-test
-class1
-QuickSortTests.java
I want to import QuickSort class and classes in common package in QuickSortTests. So the code in QuickSort.java looks like:
package com.test.class1;
import java.util.Arrays;
import com.laicode.common.*;
import com.laicode.class1.QuickSort;
class QuickSortTests {
public static void main(String[] args) {
int[] array0 = null;
QuickSort.quickSort(array0);
System.out.println(Arrays.toString(array0));
int[] array1 = new int[0];
QuickSort.quickSort(array1);
...
When I complie QuickSortTests.java in cmd using javac QuickSortTests.java, it throws an error saying:
QuickSortTests.java:4: error: package laicode.common does not exist
import laicode.common.*;
QuickSortTests.java:5: error: package laicode.class1 does not exist
import laicode.class1.QuickSort;
But in Intellij, QuickSortTests can run without any errors.

IntelliJ already knows your source layout, and even what classes are defined in what files. javac doesn't. There are multiple ways you could approach the problem, depending in part on where you want the compiled class files to go, but the simplest approach would probably be to make the root of your source tree your working directory, and run javac from there:
javac com/test/class1/QuickSortTests.java
(Or use backslashes instead of forward slashes on Windows.)
Note capitalization: I have assumed that the mismatch between the capitalization of your class names and that of the names of the files in which they reside is an error in your question. If these actually do disagree in your sources then you should fix the discrepancy.

How do I compile my main Java program on the command line when it includes an external java package?

I'm a relative Java newbie so apologies if the question appears somewhat basic. I've googled high and low for an answer here and I'm not finding anything that's helping.
Problem:
Whilst I'm able to integrate external packages into my Java programs from an IDE environment, I am trying to do run a very basic program from the command line that calls on a separate, basic package file that I have written - and am simply doing all this as I want to have a bottom-up understanding of how package files are related to a main program by Java.
I have a program that sits on my desktop named MyProgram.java:
import org.somepackage;
public class MyProgram {
public static void main(String arguments[]) {
System.out.println("Programme up and running...");
Human myHuman = new Human();
myHuman.scream();
}
Still on the Desktop, I then have another folder which I've named src, inside of which I have created the necessary subfolders corresponding to the package name, i.e. ./src/org/somepackage - and in this location, I have the Human.java file which defines the Human class with the following contents:
package org.somepackage;
public class Human {
public void scream() {
System.out.println("I exist!!");
}
}
I then created a classes folder, again on the Desktop, and ran the following compile command on the command line:
javac -d ./classes/ ./src/org/packagename/Human.java
This ran fine and created - as expected - the Human.class file within the ./classes/org/packagename/ location.
However, where I fall down is when I then try to compile MyProgram.java on the command line, i.e.
javac -cp ".:./classes/" MyProgram.java
As you'll see, my class path contains a reference to the current location (".") for the MyProgram.java file, and it contains a reference to the classes folder ("./classes/") which is the base location for the org.somepackage package inside whose subfolders (./classes/org/somepackage/) on can find the Human.class file.
At this stage, I was simply expecting the java engine to compile MyProgram.java into the program MyProgram.class - but, instead, I get an error:
MyProgram.java:1: error: package org does not exist
I've been following the instructions listed here:
https://www3.ntu.edu.sg/home/ehchua/programming/java/J9c_PackageClasspath.html
and I don't appear to be deviating from the instructions - yet I'm unable to locate an explanation on Stackoverflow or anywhere else as to a possible reason for this compile failure. If anyone has an idea, your help would be very much appreciated.
Thanks,

Your mistake is here
import org.somepackage; <--
public class MyProgram {
public static void main(String arguments[]) {
System.out.println("Programme up and running...");
Human myHuman = new Human();
myHuman.scream();
}
you forgot to import class actually, you need to write this name
import org.somepackage.Human; import all package content import org.somepackage.*; or write full qualified name of class in your code
org.somepackage.Human myHuman = new org.somepackage.Human();
myHuman.scream();
correct mistake:
import org.somepackage.Human;
public class MyProgram {
public static void main(String arguments[]) {
System.out.println("Programme up and running...");
Human myHuman = new Human();
myHuman.scream();
}
after that compile your Human.java by this command:
javac -d classes Human.java
and MyProgram.java
javac -d classes -cp "classes" MyProgram.java
and run MyProgram by
java -cp "classes" MyProgram

Java Package Execution

Here's my Situation:
I have a folder Structure:
C:\Users\user\Desktop\JavaTraining\Chapter3\examples.
examples is also a folder. Now, I have a file name Calculator.Java in Chapter3 folder with the package statement package Chapter3;. So, from the Command Line I compiled the file from the JavaTraining directory as javac Chapter3\Calculator.java, It compiled and I see a file Calculator.class generated. But when I run the command java Chapter3.Calculator from the JavaTraining Directory. It throwed me an error: Could not find file or load main class Chapter3.Calculator.
Then, I created a sub folder in Chapter3 named examples and copied the Calculator.java into the examples folder and tried compiling and executing the file thinking Chapter3 as the root folder ( executed commands from the Chapter3 directory). No error, the file got executed.
Please can anyone explain me why this happened or what is the reason behind it, I am going mad...
Calculator.java is just a class Calculator with main function trying to find a sum from a printsum function of two variables.
I went through the suggestions provided in http://stackoverflow.com/questions/18093928/what-does-could-not-find-or-load-main-class-mean
According to the above, it was either the syntax mistake ( the way of trying to executing the file) or setting the PATH and CLASSPATH environment variables.
I even tried the echo %CLASSPATH% to see if my CLASSPATH variable is set to current directory. It did show me the . when I executed the echo command from JavaTraining directory.
The file did not execute when I tried Chapter3 folder as root directory, but when I create a subfolder in Chapter3 and made Chapter3 as the root directory, it executed, what might be the reason or what am I doing wrong,
Here is the command line with the output:
C:\Users\vikas\Desktop\JavaTraining>javac Chapter3\Calculator.java
C:\Users\vikas\Desktop\JavaTraining>java Chapter3.Calculator
Error: Could not find or load main class Chapter3.Calculator
C:\Users\vikas\Desktop\JavaTraining>cd Chapter3
C:\Users\vikas\Desktop\JavaTraining\Chapter3>javac examples\Calculator.java
C:\Users\vikas\Desktop\JavaTraining\Chapter3>java examples.Calculator
The sum is 30
C:\Users\vikas\Desktop\JavaTraining\Chapter3>
The Calculator.java file:
// One Package Statement
package chapter3;
// The file in Chapter 3 folder, file in example folder has
//package examples;
// One or more import statements
import java.io.*;
import java.util.*;
// Class Declaration
public class Calculator {
// State. Variables and Constants
int i=10;
long k = 20;
// Behavior, one or more methods
void printSum(){
long sum;
sum = i+ k;
System.out.println("The sum is " + (i+k));
}
public static void main (String[] args) {
Calculator c = new Calculator();
c.printSum();
}
}

When you build a file, it is good to have a build directory, then java will put the class in the correct package layout.
mkdir build
javac -d build path/to/source/Files.java
java -cp build package.name.Files

Trouble in compiling the java code

I wrote the following piece of code in sublime text on my macbook pro.
I saved the file inside the java folder on my desktop. When I tried to compile the program and tried to execute it, I am getting the fallowing error message " Error: Could not find or load main class Animals ".
Could someone help me in compiling and running this program
package forest;
class Animals{
public static void main(String[] args)
{
Animals s = new Animals();
Sring[] s2 = s.getAllAnimals();
}
public String[] getAllAnimals()
{
String[] s1= {"Lion", "Elephant", "Tiger","Deer","Wolf","Dinosar"};
return s1;
}
}

Make your class Animal as public and rename the file to Animal.java

Your class is in a package called forest so you need to move Animals.java into a directory called forest.
You hava a typo on line 7: Sring[] s2 = should be String[] s2 =.
Compile from the parent directory of forest. Something like this should work
$ javac forest/Animals.java
Run from the parent dir:
$ java forest.Aminals
Your program will have no output when you run it.

Look on your code there is no sring type class in java so change it to String
Sring[] s2 = s.getAllAnimals();
change it to
String[] s2 = s.getAllAnimals();
Everything will be good

try this tutorial Java and the Mac OS X Terminal and Make your class public and also make sure that the file name that contains your source code and the name of your main class is same, your main class is the one that contains main method.

First of all you can name your java file with any name.
Say Sample.java. and let us consider this file is present in D:\work
Go to D:\work folder in cmd prompt.
Keep this in mind :
If you write package forest, then your class has to be public.
So write public class Animals{}
While compiling do this javac -d Sample.java
By doing this the compiler will create the folder "forest" and inside that it will create the Animals.class.
So now in D:\work we have Sample.java file and "forest" folder
Now in your command prompt DO NOT go inside the "forest" folder.
Stay in work folder. D:\work
And Run this command from D:\work java forest.Animals
Explantion::
The name of your class that contains Main method is not Animals. It is forest.Animals This is the fully qualified name of the class. This happened becasue you put a package to it.
So while runnning you must run with fully qualified name
java forest.Animals
The name of your class is not Sample.java. <-- This is just a text file name it anything the complier will not generate a class with name Sample.class because inside this file there is no such class, the class name is Animals. So Animals.class will be generated.
And javac -d Sample.java helps you create the folder structure automatically based on the package.
For example if your class was like this
package com.stackoverflow.samples
public class Animals{
}
And you do java -d Sample.java
The Compiler will create a folder com inside that another folder stackoverflow inside that another folder samples and inside that a file Animals.class
To run this you must run it from outside the the "com" folder with fully qualified name
java com.stackoverflow.samples.Animals