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Eclipse java file not found until edited and saved

I have the following file structure in my eclipse workspace
core
src
com.mygame.game (package)
Ability.java
Game.java
...
Allies-Green.java
Ability.java and Game.java were created using the 'right-click on package->New->Class' method. Allies-Green.java, however, was created using the 'right-click on package->New->File' method. Each time I load my workspace, all code that references Allies-Green.java is marked as an error. If I open Allies-Green.java though, and edit one character and resave it, the problem goes away. Does anyone know what could be causing this issue? Here is Allies-Green.java relevant code for reference:
package com.mygame.game;
import java.util.ArrayList;
import ...
//only class in file
class AllyGreen extends Ally {
...
}

Unsure about reason behind NoClassDefFoundError

I have built a DLL which I am attempting to wrap Java code with, however I am having some troubles with running my Java program. I wrote a simple test DLL and Java program and am producing the same error, and although there are plenty of resources regarding NoClassDefFoundError online I can't seem to solve mine with any troubleshooting methods.
Here is my D:\Test1.Java file
public class Test1 {
static {
//System.loadLibrary("HeyLand");
System.load("D://HeyLand.dll");
}
public native void displayHeyLand();
public static void main (String[] args) {
Test1 t = new Test1();
t.displayHeyLand();
}
}
After compiling, attempting to run D:\Test1.classresults in the following:
D:\>java Test1.class
Exception in thread "main" java.lang.NoClassDefFoundError: Test1.class
Caused by: java.lang.ClassNotFoundException: Test1.class
at java.net.URLClassLoader.findClass(URLClassLoader.java:434)
at java.lang.ClassLoader.loadClass(ClassLoader.java:660)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:358)
at java.lang.ClassLoader.loadClass(ClassLoader.java:626)
Could not find the main class: Test1.class. Program will exit.
Why I am stumped :
1. I have set my classpath to be D:\, so I believe my class definition would be in the classpath, and I do not see how my compile-time and run-time classpaths could be any different.
2. I don't see how this could have anything to do with static initialization, and I believe the exception would look different.
Perhaps I'm just missing something incredibly simple, I am very newbie with Java.
Any help is greatly appreciated!

The classpath environmental variable is taking precedence over that in the java run command. You need to specify the class location (as well as removing the .class file extension)
java -cp . Test1

Java normal syntax for executing class file is
Java [<options>....} <class-name> [<arguments>....]
For example
java com.package.name.Test1
here how compiler works
1. Compiler search for complete class name
2. Load that class
3. check for main method - in the same class
4. Call main method with passed arguments in command line string.
Now following are the possibilities why your class may not found main method.
1 - forgot to include package name
I am new developer in java but I found when I run application using eclips or intellJ editor it gives different path and package name and execute code as I noticed it on command line edior. So make sure you are including package name
For example:
java com.package.name.Test1 instead of
java Test1
2. File name or pathname rather then class name
As I noticed output file is in different location. That why class file path was different.
java Test1.class
java com/package/name/Test1.class
3. Typo
also I noticed you are using
static {
//System.loadLibrary("HeyLand");
System.load("D://HeyLand.dll");
}
Is this function ? or constructor? If it is function then where is name of the function? You cant write code without any reference in classs

java cant find or load my program when I have a package heading

I can run programs which do not have a package without any hitch. If I try and add a package then java simply cannot find them. I have set the class path and I have tried running - java packagename.ProgramName.
I have found a number of similar threads on here and have spent four hours going through all of them and trying everything and nothing works for me.
Yet as soon as I edit the .java file and recompile without a package heading - it immediately works perfectly. Why? And how can I fix it? I would like to be able to have my classes organised in packages!
This is the code I am using (I normally use eclipse and just wrote this to try out cmd out of curiosity).
package hello;
public class HelloWorldApp{
public static void helloWorld(){
System.out.println("Hello world");
}
}
and
package hello;
public class HelloBackApp{
public static void helloBack(){
System.out.println("Hello back");
}
public static void main(String[] args){
HelloWorldApp.helloWorld();
helloBack();
}
}
As I say if I delete both the package heading java HelloBackApp runs just fine.
And my path to my program is
c:\Users\sam\javastuff\hello
I have of course tried java hello.HelloBackApp from both the javastuff dir and the hello dir. No joy
It works immediately if I delete both the package headings and type java HelloBackApp from the hello directory.

try as follows,
create folder structure as your package and place java file in that folder
For ex, my java file is under
c:\code\com\test\Test.java and package is "package com.test".
I compiled and run code from
c:\code>
c:\code> javac com\test\Test.java
c:\code> java com.test.Test

Ok after much research I realised what my problem was and have fully resolved it. I think I see why I have been unable to find an "answer" to this question in forums. It is not a simple quick fix - my whole understanding of how to correctly get the class path set up and get a proper compile done was very poor. It becomes a whole new subject if you switch from compiling/running on an IDE to doing so from the command line. I think it is an excellent thing for new programmers to do though as I believe the improved understanding of CLASSPATH is going to be something that will stand us all in good stead for the future.
I found all the answers to my questions here : http://www.ibm.com/developerworks/java/library/j-classpath-windows/
and recommend anyone having similar problems I was having to read through this excellent document. Best wishes to all the other guys struggling with this out there! :)

Cannot run my own Java Package

I want to learn to write my own packages so I'm not also relient on an IDE, which I feel I have became. The problem is I cannot figure out how to run my own package, or what the proper method is to run your own package.
Here's a resource I used to learn some basics: http://javaworkshop.sourceforge.net/chapter3.html
Here's my current file structure:
Main.java
/src
projectaqua/
GameFrame.java
/classes
projectaqua/
GameFrame.class
I ran the command in the root directory of the project:javac -d ./classes/ ./src/projectaqua/*.java
I originally created a Main file in the /src/projectaqua directory and attempted to run the file. I was given this error:
Main.java:1: error: package projectaqua does not exist
import projectaqua.GameFrame;
I tried running the application in the /classes/projectaqua directory when compiling the Main file with the package, which gave me a class not defined error.
This compiled my package, the problem I'm facing is I don't understand how you are supposed to import your own package to run it, and where would the file to run the package be?
From what I've learned in school, when writing a GUI application we create a class that has a main function in it to instantiate the frame, and that's it's only job. Where would this be in this structure?
Intuitively it seems that file would be outside of the src files, but I feel like that removes the purpose of the src files. I haven't found anything useful on stackoverflow to this topic, if you do or have please point me in that direction.
More source code:
GameFrame Class:
package projectaqua;
import javax.swing.JFrame;
public class GameFrame extends JFrame
{
private int WINDOW_HEIGHT = 500;
private int WINDOW_WIDTH = 500;
private String title = "Project Aqua";
private boolean isVisible = true;
public GameFrame()
{
// Basic Window Defaults
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
setTitle(this.title);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Content Pane junk
// Will be added
setVisible(this.isVisible);
}
}
The Main class
import projectaqua.GameFrame;
public class Main
{
public static void main(String[] args)
{
GameFrame launch = new GameFrame();
}
}

I now see your problem.
In your question you were not clear that you had trouble running v. compiling. Had you posted this error trace it would have been immediately clear to me what your problem is:
unrollme-dev-dan:projectaqua Dan$ java Main
Exception in thread "main" java.lang.NoClassDefFoundError: Main (wrong name: projectaqua/Main)
Also note that had you Googled NoClassDefFoundError would have found this. The moral here is: understand and research your exact error.
Anyway
unrollme-dev-dan:classes java projectaqua/Main
is what you want. Notice the change of directory. I never bothered to understand why, has to do with relationship between package hierarchy and file structure hierarchy.
Java had two choices when designed: Assume the thing you are talking about is in the global package (yuck!) or try to guess what package it is in. It treats any folder below your working directory as packages. So even though it found a Main class in the directory from which you were running it did not find a Main class in the namespace corresponding to the directory . i.e. the global one.
When you run from one directory up and tell it to run something in projectaqua/ it is now looking for classes starting with projectaqua.
Alternately if you run
unrollme-dev-dan:projectaqua java projectaqua.Main
It looks for the right thing.

try this command at the root of your project
javac -cp ./classes -d ./classes ./src/projectaqua/*.java
Also make sure both your Main.java and GameFrame.java has package projectaqua; at the beginning

Problems when trying to compile a Hello World with Eclipse

I'm having problems when trying to compile the following code:
I first tried compiling with this code:
class HelloWorldApp {
public static void main(String[] args) {
System.out.println("Hello World!"); // Display the string.
}
}
it works as it should. Now, if I try to replace the class name for any other name, it won't work anymore, as it seems to always look after HelloWorldApp. I made sure the file is being saved and so, I even reopened Eclipse. Still the same error. Maybe this is a common problem, with a small work-around?
Thanks
edit: I see what you guys mean, but why does it work when I have the file name as "Main.java" and a class name of "HelloWorldApp" ?

You need to rename your .java file to match the class name.
Eclipse will rename your .java file to match your class name automatically if you use its refactoring support. Right click on the class name, hover over Refactor, and select the Rename option. Now when you rename your class, Eclipse will automatically rename your .java file to match.

This is how Java works. Class must have the same name as the file. So the filename for the class MyApp, must be MyApp.java

Rename main as HelloWorldApp so that your app becomes HelloWorldApp.java.

When changing the name of your class use the REFACTOR option - If you try to edit the name manually yourself the Eclipse Project loses track of your objects.