We Keep Coding

Get same JAVA compilation error as in PowerShell or CMD in Visual Studio Code

I'm on latest Windows 10. I have JDK 15. Latest Visual Studio Code (System). In VS Code, I have half of the Java Extension Pack Installed, i.e Language Support for Java (Red Hat) | Debugger for Java (Microsoft) | Visual Studio IntelliCode (Microsoft). So I did that to just get that run button on the top right (the default installed VS Code didn't have that run button for JAVA programs), below the close button, to that I can run the JAVA programs inside the VS Code. I didn't wanna go out to the directory then open Power Shell or CMD and then write java filename.java and run the program...
Now the issue is that when I click the run button, I think, a Power Shell is opened inside the VS Code and then something other than "java FileName.java" is being written. Because of that I can't really see what the compilation error is. I can only see the line number where the problem is, not actually the solution for that. || If I run the same in the PowerShell outside the VS Code with this "java FileName.java", I can see that there is some issue at x line and also the solution for the same.
So I wanted to know if there is any way to get this type of output inside the Visual Studio Code.
Or if there is any way that Instead of writing a lot of thing like this, we can simple tell the Visual Studio Code to run "java fileName.java" inside VS Code when I click the Run Button at the top.
EDIT:
The Code that I'm running is this one.....
File Name - test.java
import java.io.*;
public class SOPFileTest{
public static void main(String arr[]){
try{
// Creating a File object that represents the disk file.
PrintStream o = new PrintStream(new File("A.txt"));
// Store current System.out before assigning a new value
PrintStream console = System.out;
// Assign o to output stream
System.setOut(o);
System.out.println("Test 1");
// Use stored value for output stream
System.setOut(console);
System.out.println("Test 2");
}
catch(Exception e){
System.out.println(e.getMessage());
}
}
Now I've noticed somethings, they are:
-When (FileName == Class Name)
---Then (VS Code)
-----Prints the Last System.out.println in the console
-----A.txt is not created / written inside
---Then (Powershell)
-----Prints the Last System.out.println in the console
-----A.txt is created and/or written inside
-When (FileName != Class Name)
---Then (VS Code)
-----shows the error same as the image that I included above.
---Then (Powershell)
-----Prints the Last System.out.println in the console
-----A.txt is created and/or written inside
So powershell works as I intend it would, the VS Code isn't...

If the filename is different from ClassName, java extension will detect it and throws probelms, which is build failed and you can choose if continue:
If you choose proceed, there should be:
[UPDATE -- Screenshot in Powershell:]
It's about the same as problems shown in VS Code.
Java extension requires class must be defined in its own file, so filename should be as the same as ClassName, then everything works well, no matter in integrated Terminal in VS Code, or in the PowerShell outside VS Code:
So I wanted to know if there is any way to get this type of output
inside the Visual Studio Code.
Keeping the filename and classname same makes sure it could be built and compiled successfully, which is the first step.
And the text file should be generated in current working directory, check it in your file explorer.

Update java desktop app

I am trying to develop a module that can update my running Java Desktop App.
The problem is that I have to replace the actual running jar with another jar, all the while displaying an image and a progress bar with the remaining time of the update process.
One solution I thought about is that I can put a jar in my main jar, and when launching the update process, to extract that second jar which will display the image and the progess bar, and also which will replace the old main jar with a new main jar.
My question is if this is possible and how can I do it.
I do not have a lot of experience with java and java packaging so if you have any examples or links, it would be of great help for me.
Thank you very much.
R.

Run this code when press UPDATE button ..
if(Desktop.isDesktopSupported()){
try {
Desktop.getDesktop().open(new File("update.jar"));
System.exit(0);
} catch (IOException ex) {
}
}
This will open update.jar and close main.jar. Now run this code from main class of update.jar
//wait sometime for terminate main.jar
try{
Thread.sleep(5000);
} catch(Exception e){
e.printStackTrace();
}
if(isUpdateVersionAvailable()) { //first check update from database
if(copyMainJarFileFromServer()){ //copy newMain.jar from server and paste
new File("main.jar").delete(); //delete main.jar
rename(new File("newMain.jar")); //rename newMain.jar to main.jar
}
}
boolean isUpdateVersionAvailable() {
//todo
}
boolean copyMainJarFileFromServer() {
//todo
}
void rename(File file){
file.renameTo(new File("main.jar"));
}

You can have a starter jar that checks for updates and launches the app from the main jar.
It will show start logo, an image, that standard java can display at start-up.
The start0er could also be used to restart the app in another interface language.
package starter;
...
public class StarterApp {
public static void main(String[] args) {
String workDir = System.getProperty("user.dir");
Path mainJar = Paths.get(workDir + "...");
Path nextMainJar = Paths.get(workDir + "...");
if (Files.exists(nextMainJar)) {
Files.copy(nextMainJar, mainJar, StandardCopyAction.REPLACE_EXISTING);
}
URLClassLoader classLoader = new URLClassLoader(new URL[] {mainJar.toURL()});
Class<?> appClass = classLoader.find("mainjar.MainApp");
... instantiate the app
}
As you see the main jar must not be loaded from too early, maybe not be on the class path entirely, and hence the use of a separate ClassLoader. The same might probably be done with the main jar on the class path of the starter app, and using Class.forName("mainjar.MainApp"). The Class-Path can be specified in META-INF/MANIFEST.MF.
The secundary jars may reside in a lib/ directory.
For those readers wanting more modular, service oriented, updateable apps, one could make an OSGi application, a container for bundles (=jars), that provide exchangable services and life-time control.

How to input a file in this code?

I am still a Java newbie and I have this code. I don't know how to pass the input file to the code. I am using Eclipse Juno.
public static void main(String[] args) {
In in = new In(args[0]); // input file
int N = in.readInt(); // N-by-N percolation system
// turn on animation mode
StdDraw.show(0);
// repeatedly read in sites to open and draw resulting system
Percolation perc = new Percolation(N);
draw(perc, N);
StdDraw.show(DELAY);
while (!in.isEmpty()) {
int i = in.readInt();
int j = in.readInt();
perc.open(i, j);
draw(perc, N);
StdDraw.show(DELAY);
}
}
Whenever I run it I get this exception:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at PercolationVisualizer.main(PercolationVisualizer.java:42)
What might cause this exception? Could you please be patient with me and explain the process of how to call the input file in the code?

Refer to this guide for adding arguments to your program. Alternatively, you could specify the file name directly in the code instead of reading it from the args.
Basically, the guide instructs the user to go to the Run menu, then "Run..." (actually "Run Configurations..." in recent Eclipse versions), select the appropriate run configuration for the desired project, click the Arguments tab, and enter the arguments (such as file name) in the "Program arguments" section, separated by spaces.

For those using IntelliJ you can set the program arguments via Run->Edit Configuration. Look down about the middle of the window to locate the "Program Arguments" field. Then add the path to the test file and save.

Working with file in Eclipse

I have instruction to run program in command line, for example:
java SetTest < alice30.txt
I wonder how to do this in Eclipse. I tried to put this in Run Configuration like this:
Another thing I don't know is where to put this file (alice30.txt). Is this in root of project or in src folder where source files are located?
I know these are beginner questions but I am stuck and need help.
EDIT:
As #Kane suggested I passed File and opened stream.
Instead of:
Scanner in = new Scanner(System.in);
I now use:
Scanner in = new Scanner(new File("alice30.txt"));

You can pass full file path in arguments (e.g. c:/.../alice30.txt))

The eclipse root directory is the base directory of the project (i.e., not the src/ directory, directly under the project.)
It's generally good style to have a 'resources' folder for txt, graphics, etc.
Rather than trying to pass a stream you could just pass the filename and open the stream yourself.
The reason what you're doing in Eclipse isn't working is because your command prompt/shell/dos/bash/whatever is handling creating the input stream out of the file for you. Eclipse doesn't do this. So, from the command line: < alice.txt means "run this program with no arguments, and create a stream to system.in", while doing that in Eclipse means "run this program with two arguments '<' and 'alice.txt'

you need do like this:
add:
import java.io.IOException;
import java.nio.file.Paths;
then:
replace"Scanner in = new Scanner(System.in);"to"Scanner in =new Scanner(Paths.get("alice30.txt"));" .
and you also need do this : "public static void main(String args[]) throws IOException "

With information from this link/page and several tries, I figure out a way to pass argument and file using the local route in eclipse Run -> Run Configurations.. , though it is not recommended as Kane said.
For my case: I need to do " $java someClass tinyW.txt < tinyT.txt " (This is an example from Algorithms book by Robert Sedgewick)
In my case, " tinyW.txt " is a argument, so in the eclipse environment, you can set in Run -> Run Configurations -> Arguments -> Program arguments: /local address/tinyW.txt. For my Ubuntu: /home/****/tinyW.txt
" < tinyT.txt " is a file that pipe to the main arguments, so you can set the route and file in " Run -> RUn Configurations -> Common ", click the "Input File", use the File System icon and select the file from local compute. See the figure. So in Input File: /local_address/tinyT.txt. My case is: /home/***/tinyT.txt. Hope it also works for you.

Cannot run "Hello World" program in Eclipse

I have an error in my first step with Java, so when i try to run the code hello world:
class apples{
public static void main(String args[]){
System.out.println("Hello World!");
}
}
I go to: - Run as .. -> Then i choose Java aplicacion - > And i press Ok
But when i press Ok does not appear the window down to show me the correct message Hello World

Your code works fine for me:
class apples
{
public static void main(String args[])
{
System.out.println("Hello World!");
}
}
I downloaded it to c:\temp\apples.java.
Here's how I compiled and ran it:
C:\temp>javac -cp . apples.java
C:\temp>dir apples
Volume in drive C is HP_PAVILION
Volume Serial Number is 0200-EE0C
Directory of C:\temp
C:\temp>dir ap*
Volume in drive C is HP_PAVILION
Volume Serial Number is 0200-EE0C
Directory of C:\temp
08/15/2010 09:15 PM 418 apples.class
08/15/2010 09:15 PM 123 apples.java
2 File(s) 541 bytes
0 Dir(s) 107,868,696,576 bytes free
C:\temp>java -cp . apples
Hello World!
C:\temp>
Your lack of understanding and the IDE appear to be impeding your progress. Do simple things without the IDE for a while until you get the hang of it. A command shell and a text editor will be sufficient.
Sorry about missing javac; cut & paste error.

If you look at the screenshot, your class name is there, last in the list. Select it and press OK. To not see this message again, right-click on the class name on the left side and select there Run...->Java Application.

The only problem that causes your error here is that the classname and the filename do not match - and they have to.
Solution
Rename either the file thesame.java to apple.java or the class to thesame. Then if you select "Run as..." again, eclipse will present a menu item to start your Java application.
(other mentioned, that there's no requirement that a top-level class and the filename do match - unless the top level class is public. Of course this is true. But the problem was about "running" a class under eclipse as a Java application)

Try public class apples and make sure the file is apples.java. Also it should be public static void main(String[] args)

You have 2 classes by name of "thesame.java" under the source folder. Since one is directly under the src folder, and other under (default package), they use the same namespace, hence Interpreter is confused which java file to execute and is asking you to select the class you want to execute.

Class names must be capitalized... so change apples to Apples. Also, if you are a beginner (which it seems like), I would recommend the Netbeans IDE -- it's a bit more friendlier for new users than Eclipse.

You class must be named "thesame" if you store it in a file called "thesame.java", as you have. Either rename your class to "thesame" or change the file to be "apples.java".
You should move the "[]" to be before "args". So, String[] args.
Either select "apples" at the bottom of the menu you posted and run it, or right-click on the Java file and make it the default thing to run for this project. Or launch it by right-clicking on the file and selecting "run".