Everything worked perfectly until I had to brute-force restart notebook with opened java project ( 1 java class which was compiled ). After the reboot i opened intellij created a new project ( the old was not saved ) , then in src folder created a java class but whenever I want to Run it I get only "Edit the configuration" and do not know what to do.
Also when i write some piece of code like:
import java.util.*;
public class Main
{
public static void main( String[] args )
{
List<String> list = new ArrayList<String>();
list.add( "Example" );
}
}
The add method is red and it says Cannot resolve the symbol add().
This happens with every method even to System.out.println()
I will be very thankful for your suggestions. ( Btw I'm using intellij ultimate version, Linux Mint 17 ).
Please read compiler messages more carefully.
List<String> list = new String<String>();
Doesnt work - try:
List<String> list = new ArrayList<>();
for example!
So, the real lesson here is not that you made a little typo. It is about the fact that you can trust on compiler error messages to a high degree! So, before you think "is my project broken"; you look at your source code and any error message really really carefully.
Stop Intellij, remove the .idea folder and .iml file from the directory, then restart. You'll have to create a new project from the code, but it should work. If you continue to have problems, go to the File menu and selected "Invalidate caches/restart". Choose "Invalidate and restart."
Related
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.
Eclipse give error when I try to compile and run to JAVA codes. The error is
"The selection cannot be launched, and there are no recent launches".
How to fix this issue ??
your code is wrong. you need a main method to launch your program
package main;
public class main {
public static void main (String[] args) {
System.out.println("Test");
}
}
Note: The name of the class always has to be the name of the file, and typically java classes start with an uppercase letter
I think you should run main first and describe your problem in more detail if you still have a problem.
Q: When I try to run my project by clicking the green "Play" button, I get an error of, "The Selection cannot be launched, and there are no recent launches."
A: See previous question. You must run your project's "Main" class at least once by using the right-click method described above, before the "Play button" to run a project will work.
http://courses.cs.washington.edu/courses/cse143/15wi/eclipse_tutorial/faq.shtml
First of all I would like to thank in advance everyone for reading such a long post. I really appreciate your help.
The thing is that I've been doing some research on how to "connect" Matlab and Java for a project I am working on for university. I figured that the most suitable option was using Matlab Builder JA, but I'm having a lot of troubles with it.
I follow step by step the instructions described on a tutorial (the link of the video in below) but get compilation errors over and over, and I really don't know how to fix them. The tutorial is about creating a Java package (demo.jar) with MATLAB ("com.demo"), which contains a class (MLTestClass) with a function makeSqr(n) which returns an n × n square matrix. Then I go to Eclipse, I add to the project both libraries javabuilder.jar and demo.jar and then create the following class:
public class Driver {
public static void main (String[] args) {
MLTestClass x = null;
Object result [] = null;
try {
x = new MLTestClass ();
result = x.makeSqr (1, 5);
System.out.println (result [0]);
} catch (MWException e) {
e.printStackTrace();
}
}
}
Of course I import com.demo.* and com.mathworks.toolbox.javabuilder.*.
Here are the errors the console gives me:
Exception in thread "main" java.lang.ExceptionInInitializerError
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration.getProxyLibraryDir(MCRConfiguration.java:163)
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$MCRRoot.get(MCRConfiguration.java:77)
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$MCRRoot.<clinit>(MCRConfiguration.java:87)
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration.getMCRRoot(MCRConfiguration.java:92)
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$ModuleDir.<clinit>(MCRConfiguration.java:66)
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration.getModuleDir(MCRConfiguration.java:71)
at com.mathworks.toolbox.javabuilder.internal.MWMCR.<clinit>(MWMCR.java:1573)
at com.demo.DemoMCRFactory.(DemoMCRFactory.java:122)
at com.demo.MLTestClass.(MLTestClass.java:63)
at Driver.main(Driver.java:12)
Caused by: java.lang.NullPointerException
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$ProxyLibraryDir.get(MCRConfiguration.java:143)
at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$ProxyLibraryDir.<clinit>(MCRConfiguration.java:158)
... 10 more
Just in case, link tutorial (it's the video): http://www.mathworks.nl/products/javabuilder/description2.html
Anyone has any ideas what the problem could be? It says something about NullPointerException, but I don't know how to solve it as the constructor is provided by the class created with MATLAB. I didn't have any issues installing MCR, and by the way I have MacOS, which I hope is not the source of the problem :).
Again, sorry for the long post and thank you for your time.
Béntor.
Yes, please install MCR. The installation also mentions about setting environmental variables like LD_LIBRARY_PATH etc. If you are using eclipse, i would recommend you update the environmental variables
right click->
properties ->
run/debug settings->
environmental variables
I also had to make sure that variable MCR_CACHE_ROOT pointed to different directory since my home directory was not big enough.
You have install MCR (avaliable in http://www.mathworks.com/products/compiler/mcr/index.html)
None of the above solutions helped me (I already had MCR installed and Macs use DYLD_LIBRARY_PATH instead of LD_LIBRARY_PATH), and noone else online seemed to know. Finally in desperation, I tried editing the DYLD_LIBRARY_PATH and finally got it to work by removing the last part of it: /Applications/MATLAB/MATLAB_Compiler_Runtime/v82/sys/java/jre/maci64/jre/lib
Now the demo application from the tutorial works.
Next comes trying to make my code work.
OS X Paths for Run-Time Deployment
Use these setenv commands to set your MATLAB Runtime paths.
setenv DYLD_LIBRARY_PATH \
mcr_root/version/runtime/maci64 \
mcr_root/version/bin/maci64 \
mcr_root/version/sys/os/maci64
Source: http://www.mathworks.com/help/compiler_sdk/java/mcr-path-settings-for-run-time-deployment.html
I am new to java and to the eclipse IDE.
I am running Eclipse
Eclipse SDK
Version: 3.7.1
Build id: M20110909-1335
On a windows Vista machine.
I am trying to learn from the book Thinking in Java vol4.
The author uses his own packages to reduce typing. However the author did not use Eclipse and this is where the problem commes in..
This is an example of the code in the book.
import java.util.*;
import static net.mindview.util.print.*;
public class HelloWorld {
public static void main(String[] args) {
System.out.println("hello world");
print("this does not work");
}
this is the contents of print.Java
//: net/mindview/util/Print.java
// Print methods that can be used without
// qualifiers, using Java SE5 static imports:
package net.mindview.util;
import java.io.*;
public class Print {
// Print with a newline:
public static void print(Object obj) {
System.out.println(obj);
}
// Print a newline by itself:
public static void print() {
System.out.println();
}
// Print with no line break:
public static void printnb(Object obj) {
System.out.print(obj);
}
// The new Java SE5 printf() (from C):
public static PrintStream
printf(String format, Object... args) {
return System.out.printf(format, args);
}
} ///:~
The error I get the most is in the statement.
Import static net.mindview.util.print.*;
On this staement the Eclipse IDE says it cannot resolve net
also on the
print("this does not work");
The Eclipse IDE says that the class print() does not exist for the class HelloWorld.
I have been trying to get these to work, but with only limited success, The autor uses another 32 of these packages through the rest of the book.
I have tried to add the directory to the classpath, but that seems to only work if you are using the JDK compiler. I have tried to add them as libraries and i have tried importing them into a package in a source file in the project. I have tried a few other things but cant remember them all now.
I have been able to make one of the files work, the print.java file I gave the listing for in this message. I did that by creating a new source folder then making a new package in that foldeer then importing the print.java file into the package.
But the next time I try the same thing it does not work for me.
What I need is a way to have eclipse load all these .java files at start up so when I need them for the exercises in the book they will be there and work for me, or just an easy way to make them work everytime.
I know I am not the only one that has had this problem I have seen other questions about it on google searches and they were also asking about the Thinking In Java book.
I have searched this site and others and am just not having any luck.
Any help with this or sugestions are welcome and very appreciated.
thank you
Ok I have tried to get this working as you said, I have started a new project and I removed the static from the import statement, I then created a new source folder, then I created a new package in the source folder. Then I imported the file system and selected the the net.mindview.util folder.
Now the immport statement no longer gives me an error. But the the print statement does, the only way to make the print statement work is to use its fully qualified name. Here is the code.
import net.mindview.util.*;
public class Hello2 {
public static void main(String[] args) {
Hello2 test = new Hello2();
System.out.println();
print("this dooes not work");
net.mindview.util.Print.print("this stinks");
}
}
The Error on the print statement is:
The method print(String) is undefined for the type Hello2
and if I try to run it the error I get is:
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
The method print(String) is undefined for the type Hello2
at Hello2.main(Hello2.java:6)
The Statement::::: net.mindview.util.Print.print("this stinks") is the fully qualified print statement and it does not throw an error but it does totally defeat the purpose of the print.java file..
If you have any questions please ask Ill get back to you as soon as I can.
I've had similar issues. I solved it by following the steps below:
Click File->New->Java Project. Fill in UtilBuild for the ProjectName. Chose the option "Use project folder as root and click 'Finish'.
Right-click on UtilBuild in the PackageExplorer window and click New->package. For the Package Name, fill in net.mindview.util
Navigate within the unzipped Thinking In Java (TIJ) folder to TIJ->net\mindview\util. Here you will find all the source code (.java) files for util.
Select all the files in the net\mindview\util folder and drag them to the net.mindview.util package under UtilBuild in Eclipse. Chose the 'Copy Files' option and hit 'OK'.
You will probably already have the 'Build Automatically' option checked. If not, go to Project and click 'Build Automatically'. This will create the .class files from the .java source files.
In Eclipse, right-click on the project you were working on (the one where you couldn't get that blasted print() method to work!) Click Properties and Java Build Path->Libraries. Click 'Add Class Folder...' check the box for UtilBuild (the default location for the .class files).
I think the confusion here arises due to CLASSPATH. If you use Eclipse to build and run your code then Eclipse manages your CLASSPATH. (You don't have to manually edit CLASSPATH in the 'Environment Variables' part of your computer properties, and doing so changes nothing as far as Eclipse Build and Run are concerned.)
In order to call code that exists outside your current project (I will name this 'outside code' for convenience) you need to satisfy three things:
A. You need to have the .class files for that code (as .class files or inside a JAR)
B. You need to indicate in your source code where to look for the 'outside code'
C. You need to indicate where to start looking for the 'outside code'
In order to satisfy these requirements, in this example we:
A. Build the project UtilBuild which creates the .class files we need.
B. Add the statement import static net.mindview.util.Print.*; in our code
C. Add the Class Folder library in Eclipse (Java Build Path->Libraries).
You can investigate the effect of Step C by examining the .classpath file that lives directly in your project folder. If you open it in notepad you will see a line similar to the following:
<classpathentry kind="lib" path="/UtilBuild>
You should combine this with your import statement to understand where the compiler will look for the .class file. Combining path="/UtilBuild" and import static net.mindview.util.Print.*; tells us that the compiler will look for the class file in:
UtilBuild/net/mindview/util
and that it will take every class that we built from the Print.java file (Print.*).
NOTE:
There is no problem with the keyword static in the statement
import static net.mindview.util.Print.*;
static here just means that you don't have to give specify the class name from Print.java, just the methods that you want to call. If we omit the keyword static from the import statement, then we would need to qualify that print() method with the class it belongs to:
import net.mindview.util.Print.*;
//...
Print.print("Hello");
which is slightly more verbose than what is achieved with the static import.
OPINION:
I think most people new to Java will use Eclipse at least initially. The Thinking in Java book seems to assume you will do things via command line (hence it's guidance to edit environment variables in order to update CLASSPATH). This combined with using the util folder code from very early in the book I think is a source of confusion to new learners of the language. I would love to see all the source code organised into an Eclipse project and available for download. Short of that, it would be a nice touch to include the .class files in just the 'net/mindview/util' folder so that things would be a little easier.
U should import package static net.mindview.util not static net.mindview.util.Print
and you should extend the class Print to use its method.......
You should remove the static keyword from your import decleration, this: import static net.mindview.util.print.*; becomes this: import net.mindview.util.print.*;
If that also does not work, I am assuming you did the following:
Create your own project;
Start copying code directly from the book.
The problem seems to be that this: package net.mindview.util; must match your folder structure in your src folder. So, if your src folder you create a new package and name it net.mindview.util and in it you place your Print class, you should be able to get it working.
For future reference, you should always make sure that your package decleration, which is at the top of your Java class, matches the package in which it resides.
EDIT:
I have seen your edit, and the problem seems to have a simple solution. You declare a static method named print(). In java, static methods are accessed through the use of ClassName.methodName(). This: print("this dooes not work"); will not work because you do not have a method named print which takes a string argument in your Hello2 class. In java, when you write something of the sort methodName(arg1...), the JVM will look for methods with that signature (method name + parameters) in the class in which you are making the call and any other classes that your calling class might extend.
However, as you correctly noted, this will work net.mindview.util.Print.print("this stinks");. This is because you are accessing the static method in the proper way, meaning ClassName.methodName();.
So in short, to solve your problem, you need to either:
Create a method named print which takes a string argument in your Hello2 class;
Call your print method like so: Print.print("this stinks");
Either of these two solutions should work for you.
In my case I've dowloaded and decompressed the file TIJ4Example-master.zip. in eclipse workspace folder. The three packages : net.mindview.atunit, net.mindview.simple and net.mindview.util are in this point of the project :
and java programs runs with no problems (on the right an example of /TIJ4Example/src/exercises/E07_CoinFlipping.java)
Dunno why this happens... Ok here is the situation: I have a nb project on my laptop. I have the same project on my desktop. I copy the sources (not the entire project) on the desktop, overwriting the desktop sources. Everything cleans and builds ok. Then I start the debugger. On the main class I can debug step by step. If it goes into an internal method here is what happens:
Listening on 37574
User program running
LineBreakpoint test.java : 45 successfully submitted.
Breakpoint hit at line 45 in class test by thread main.
Thread main stopped at test.java:45.
User program running
Not able to submit breakpoint LineBreakpoint baseControllerManager.java : 41, reason: No executable location available at line 41 in class baseClasses.JNW.baseControllerManager.
Invalid LineBreakpoint baseControllerManager.java : 41
Debugger stopped on uncompilable source code.
User program finished
As you can see until I'm in static method main it works (line 45) as I jump inside a non static method (that is an override) it comes out with that... I tried to:
clean and build = no effect
manually delete build and dist = no effect
What do you suggest?
For the sake of completeness I'm attaching the sources of the main class:
import baseClasses.JNW.baseAction;
import baseClasses.JNW.baseContResult;
import baseClasses.JNW.baseController;
import baseClasses.JNW.baseControllerManager;
public class test {
public static class starter extends baseController {
public static final String ACTION_START = "ACTION_START";
#Override
public baseContResult doAction(baseAction action) {
if (ACTION_START.equals(action.action)) {
manager.log("action start...");
return new baseContResult(RESULT_OK, baseContResult.resultType.RESULT_OK);
}
return super.doAction(action);
}
#Override
public void init() {
super.init();
}
}
public void startMe() {
baseControllerManager manager;
try {
manager = new baseControllerManager();
} catch (Exception e) {
e.printStackTrace();
return;
}
starter st = new starter();
manager.setMainController(st);
manager.doAction(new baseAction(starter.ACTION_START));
}
public static void main(String args[]) {
test te = new test();
te.startMe();
}
}
Look in the file nbproject/project.properties for the property javac.debug and make sure that it's "true". If it is, grep for that property elsewhere in the nbproject directory and any local ant settings.
On a semi-related note: when I'm creating a project in NetBeans, even if the sources already exist elsewhere, I always create a new "Java Application", and let it populate the project directory as it wants. Then I can move in my sources and update the project, and NetBeans stays happy.
Edit after you tried setting javac.debug:
Looking at your question again, I see that you were able to set a breakpoint on test.java, but not able to set one on baseControllerManager.java. That indicates to me that you're getting the latter class from a JAR somewhere, not from your project directory.
So the first step is to make sure that you haven't defined a CLASSPATH environment variable. This is never a good thing to do, regardless of whether you're using an IDE or a manual build.
Next step is to look at the libraries that you've specified for the NetBeans project. You can use grep on a JARfile; the file directory is in plaintext. It should be sufficient to look for the unqualified classname.
And the final thing is to verify that you are indeed compiling the class, by looking for it in the build directory.
Generally, an uncompilable error means a symbol could not be resolved.
If you have dependencies on other projects, libraries, or jars, make sure they have built successfully / are present.
Checking "Build Projects on Classpath" (in project properties > Build > Compiling) will often fix this. If you don't have this checked, you are responsible for ensuring dependencies are already built.
The property was not present in project.properties. So I added it (at a point where there where many javac.* properties...). Then I grepped like this:
dario#dario-desktop:~/Scrivania/JNW$ grep -r javac.debug *
nbproject/project.properties:javac.debug=true
nbproject/build-impl.xml: <property name="javac.debug" value="true"/>
nbproject/build-impl.xml: <attribute default="${javac.debug}" name="debug"/>
nbproject/build-impl.xml: <javac debug="#{debug}" deprecation="${javac.deprecation}" destdir="#{destdir}" encoding="${source.encoding}" excludes="#{excludes}" fork="${javac.fork}" includeantruntime="false" includes="#{includes}" source="${javac.source}" sourcepath="#{sourcepath}" srcdir="#{srcdir}" target="${javac.target}" tempdir="${java.io.tmpdir}">
nbproject/private/private.properties:javac.debug=true
nbproject/project.properties~:javac.debug=true
In fact it sees my addition on the last line.
I cleaned and rebuilt the project. The debugger is not working again........... I think I'll kick my boss ass until he agrees to use eclipse or he fires me. I'll be unemployed but happy. Apart from joking, #kdgrgory, do you have any more ideas???
I had the same problem and found that if I run clean from project tab it solves the problem.