We Keep Coding

How to specify which implementation to test

My professor has given us an assignment to implement two interfaces and he has built a tester for each interface. I have written my code, but when I run the testers I always get stuck at the line to specify which implementation to test. Here is a link to the website so you can view the testers. I have no idea what to do. If I need to provide anymore information let me know.
https://www.cct.lsu.edu/~sbrandt/csc1351/06/1351-merge-sort.php

In MTester.java and MTesterL.java, you can see the line Class<?> c = Class.forName(args[0]); . That means that you need to pass to the java test program the name of your Implementation. Look how to pass args to main here: https://stackoverflow.com/a/19648592/5947244

When I understand your problem and the tester code currently, you need to pass the full class name of your implementation as the command line argument of the program.
Assuming all the source files are the current directory and all are in the default package (have no package declared on top) and your implementation is in a file MSorter.java, the command line could look like:
> javac -cp . *.java
> java -cp . Tester MSorter
> java -cp . MTesterL MSorterL

Which class gets called first in a java project with many packages? [duplicate]

This question already has answers here:
Is the Main method must needed in a Java program?
(9 answers)
Closed 7 years ago.
Is there a class called 'main' or something that java looks for in your project?
If it finds it, does the compiler take the 'main.class' as a starting point for compilation?
I don't know what to call my main class, whether there is even such a thing, or if more than one class act in tandem to control how the program works &/or call all the other classes.
I have a little experience in programming Minecraft mods, but that is also a bit scanty, so it would be awesome if you guys helped me out =]

When the JVM starts it will run a method named main with the signature:
public static void main(String args[])
When you start the JVM you tell it which class to use to find the main method. Alternatively you can start the JVM with a jar file, in which case it will look at the manifest in order to determine which class's main method to use.
For the jar method you execute the JVM like java -jar myjar.jar and define the main class in the manifest file with the Main-Class attribute.
Otherwise you start the JVM like java com.package.MyMainClass

At compilation time, it doesn't usually matter - you just specify all the source files you want to compile. (You can specify a subset and the compiler will find other source files it needs, but it's better to specify everything you want compiled.)
When you execute a Java program from the command line, you specify the class containing the main method:
java com.foo.MyAwesomeApp

In runnable jar files, there should be META-INF/MANIFEST.MF file with Main-Class specified.

Issue running java program from batch file, runs fine in IDE

I'm doing some basic java homework for a class on my new laptop - issue is, I can't seem to get the program to compile and run from my batch file using the directions the instructor gave me.
I've set the Path variable to my JDK inside the Environment Variables settings.
My program is a simple shipping program to keep track of shipment information - I have the program working flawlessly in NetBeans (which our instructor advised us to use for developing the code), but he's going to be testing them using batch files, so we're also advised to test them on our systems with one we create prior to turning them in - pretty straightforward.
Issue is, I cannot seem to get this to work. I've never done it before, but I've used .bat files to compile and run C++ programs, as well as using makefiles on a unix system, so I feel like I'm absolutely stupid for not figuring this out on my own, but none of my searches have returned any fruitful solutions that help at all.
My program consists of 3 .java files:
Shipment.java - an interface that contains abstracted methods that are implemented in the ShipmentHW1 class
ShipmentHW1.java - a class that implements the abstracted methods from Shipment and has constructors, etc to create a usable object
TestShipment.java - the main class of this program, which utilizes and creates ShipmentHW1 objects based on preset parameters. This is super duper basic stuff here, and again, it runs perfectly fine inside the NetBeans IDE.
The instructions given to us state to have the batch file inside the package directory (which in this case I've set aside a seperate folder on my desktop titled "shipping", which is the package name - shouldn't be any issues there), where the 3 .java files are located as well.
They say if you don't need to explicitly list the path to the JDK, then you can simply have
javac TestShipment.java
java TestShipment.java
pause
Afterwards I get errors talking about how it "cannot find symbol Shipment s = new ShipmentHW1();"
I've tried adding imports, but since they're in the same package it shouldn't even be an issue.
Directory path is
C:\Users\X\Desktop\shipping
All 7 files are contained within:
TestShipment.java
TestShipment.class
Shipment.java
Shipment.class
ShipmentHW1.java
ShipmentHW1.class
doHW1.bat
Does anyone have any idea? I can provide more information if I've been too vague
Also, I'm on Windows 8 if that makes any difference

Solved
Batch file now reads
javac TestShipment.java Shipment.java ShipmentHW1.java
cd ..
java shipment.TestShipment
pause
and it works like a charm. Anyone have any ideas why I had to call the package.class instead of just compiling it regularly?

Try doing
javac TestShipment.java
java TestShipment
pause

Without seeing the contents of TestShipment.java, I'll assume you have some dependency on the Shipment and ShipmentHW1 classes. As such, when you execute a program that uses the TestShipment class, you need to have the .class files for each of the three (and any other dependencies).
So you will have to compile Shipment.java and ShipmentHW1.java as well before running your java command. If they are in the same package, you're good, if not, you will have to specify an appropriate value for the -cp option.
When running java with a class name, you need to specify the fully qualified class name.

If your .java files are declared to be in the 'shipping' package, then you probably need to be running java from the parent directory of 'shipping', e.g.
cd <path>/shipping
javac TestShipment.java
cd ..
java shipping/TestShipment

How to create a method out of the text file?

I have a text (.txt) file that contains Java code! I want to create a method that includes this Java code and then call that method through the program.
Can anybody suggest a way to do this?

let consider this example what it does actually load the source code, compile and execute the java code by simpler program by using JavaCompiler API.

Use the JavaCompiler. It can compile code from a String, so I'm sure it could handle code from a text file.
Do you think instead of putting it in the main method I can put it in for example test method and call method like this?
Put it wherever you like. E.G. see the STBC & especially the source code. It provides a GUI and can compile the code in the text area on button click.
this program need tools.jar but jre 7 doesnt have this!!
Did you try reading the documentation that is provided for the STBC? Notably:
System Requirements
STBC will run on any computer with a version 1.6+ Java Plug-In* JDK (AKA SDK).
(*) The API that STBC uses is merely a public interface to the compiler in the tools.jar that is distributed only with JDKs (though the 'public JRE' of the JDK also seems to acquire a tools.jar). This leads to some unusual requirements in running either the native jar, or the web start app.
Or shorter, no JRE will have a JavaCompiler, only JDKs have them.

Change the .txt file to a .java file,
add it to your java project
Compile the code
Execute the methods

Load the file in through standard java IO and then have Groovy evaluate it for you:
http://groovy.codehaus.org/Embedding+Groovy

it's something like quine:
http://www.nyx.org/%7Egthompso/quine.htm

Is there a way to run short bits of Java code without compiling?

Is there a way to run or simulate running Java statements (kind of like IDLE - the Python GUI) without compiling and running the executable? I want to quickly test statements to see if they work. Thanks.

Yep, you can use Eclipse, create a single project, and create a Scrapbook Page in that project.
You can also specify import statements: http://www.informit.com/articles/article.aspx?p=31789&seqNum=3
Scrapbook pages get their classpath
from the containing project's build
path. If in a scrapbook page you want
to reference a Java element that is
not on the build path of the
containing Java project, you need to
add to the Java project's build path.
Scrapbook pages also allow you to
specify import statements. You do this
by selecting Set Imports from the
context menu of a scrapbook page or
Set Import Declarations for Running
Code from the toolbar. You need to set
import statements for references to
Java declarations in your projects.
This is a common oversight. If the
type or package you are attempting to
import is not listed in the Add
dialog, it means you need to add it to
the build path of the project
containing the scrapbook page. If you
are referencing an element that has
multiple declarations, you will need
to add an import statement to uniquely
identify the element.
Edit: Got another solution too: http://ideone.com. It's an online IDE and debugging tool. You can see an example here: http://ideone.com/98sA8, but it looks like you have to set up a bit more than on a scrapbook page.
Edit 2:
Nowadays in Java 11, if it's a simple app in a single file you can run it directly from the java command (on the command line) which will handle all the compilation for you behind the scenes:
java HelloWorld.java
This is useful for students, as they can get started with Java without learning all of the javac compilation routine.

As of Java 11 (JEP 330) it is now possible to run Java files directly with the java tool:
java Factorial.java 3 4 5
is informally equivalent to
javac -d <memory> Factorial.java
java -cp <memory> Factorial 3 4 5
Java also added support for "shebang" files.
For more details see:
http://openjdk.java.net/jeps/330

Using Eclipse, you can create a Scrapbook page which will allow you to do exactly this.
Caveats:
You need to use full binary class names for anything outside of java.lang
You need to select the code (standard text selection) that you want to run
There are three different methods for running -- Inspect, Display, and Run. Inspect and Display are virtually the same, showing you the result of the last statement in your code (so you don't need to print it or anything), Run runs the selected code and dumps any output to the console view.

Never used it, but BeanShell seems to do what you want

You should be able to use Beanshell to do this:
http://www.beanshell.org/download.html
Your other alternative, if you're using Eclipse, is to make use of the scrapbook functionality:
http://help.eclipse.org/helios/index.jsp?topic=/org.eclipse.jdt.doc.user/tasks/task-create_scrapbook_page.htm

You can accomplish this with Groovy and the Groovy Console, with the caveat that you'd need to know how to express whatever you are trying to express in Java in the Groovy language:

you might want to checkout janino http://docs.codehaus.org/display/JANINO/Home also ..

JGrasp is the best solution. There is a thing called interactions, that's perfectly fine.

Use JShell, which is included by default starting from JDK 9. It is command-line based Read Eval Print Loop (REPL), where you can enter Java code, and get the results immediately.