OK, I just cannot get java to run my .class files:
I follow steps in Oracle tutorial and try to run this program:
class HelloWorldApp {
public static void main(String[] args) {
System.out.println("Hello World!"); // Display the string.
}
}
Compiling OK:
PS C:\Users\Ztaz> javac .\HelloWorldApp.java
But after I try to run it, I get this:
PS C:\Users\Ztaz> java .\HelloWorldApp.class
Error: Could not find or load main class .\HelloWorldApp.class
no exception, nothing.
Here's my PATH variable, if it helps (split into lines, for readability):
%JBOSS_HOME%;
%SYSTEMROOT%;
%M2%;
%JAVA_HOME%\bin;
...
JAVA_HOME is set to "C:\Program Files\Java\jdk1.7.0". My question sounds a lot like this one but I had this problem on Java SE 6 as well, so I decided to post separate question.
Run it without the .class: java HelloWorldApp
This causes issues for lots of people starting out with Java. Not sure why Java doesn't just look for both files (the name provided and the name with .class appended).
Related
Using Java 8
I have set my PATH as 'C:\Program Files\Java\jdk1.8.0_144\bin'
I also tried to set my CLASSPATH as 'C:\Program Files\Java\jre1.8.0_144\lib\rt.jar', though I read it is not neccesary.
From Class01.java I have no problem creating Class01.class
javac Class01.java -> created Class01.class
Still, when I try to run program
java Class01
I got message
Error: Could not find or load main class Class01
If anyone know, how to fix this, I appreciate every hint.
Btw. My program does nothing but printing Hello world, if it has something to do with my problem.
You will need to tell Java about the classpath where it should find your file. I think you are missing the classpath parameter in your java command (see below). Here is a simple example how you could create a java file, compile and run it:
A. Create File:
public class X {
public static void main(String[] args) {
System.out.println("Blah!");
}
}
B. Compile:
"%JAVA_HOME%\bin\javac" X.java
C. Run it using the `-classpath` parameter:
"%JAVA_HOME%\bin\java" -classpath . X
This will print out:
Blah!
Note that JAVA_HOME is a System variable in Windows which needs to point to the location of your Java Runtime Environment.
This question already has answers here:
What does "Could not find or load main class" mean?
(61 answers)
Closed 7 years ago.
I write a simple program using java language, then try to compile and run it on Windows console, the compile is ok, but when I try to run it with command line '>java HelloWorld', the console reports 'Error: Could not find or load main class', this is my code(c:\Sample\HelloWorld.java) as below:
package com.sample.test;
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello world");
}
}
If I comment out the line "package com.sample.test", try the compile and run command lines again, everything is ok, I can't understand why. Here is the environment variables in my computer:
JAVA_HOME=C:\Program Files\Java\jdk1.8.0_40
Path=%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;
CLASSPATH=.;%JAVA_HOME%\lib;%JAVA_HOME%\lib\tools.jar
My question is if I still want to reserve the package declaration, how can I run my program?
If you want to put your main class into a package, then you also have to give that package name when running it:
java com.sample.test.HelloWorld
And you have to make sure the class file can be found. You cannot run java from the directory that contains HelloWorld.class. You have to run it from the directory that contains the com folder (or adjust your classpath).
I'm getting the error Error: Could not find or load main class ExcelFileEditor when trying to run my program. I compiled the program with no errors by:
javac -cp C:\Users\rperera\IdeaProjects\LinkingNames\libs\*;. C:\Users\rperera\IdeaProjects\LinkingNames\src\ExcelFileEditor.java
I tried doing:
java ExcelFileEditor
java -cp C:\Users\rperera\IdeaProjects\LinkingNames\libs\* ExcelFileEditor
but I keep getting the same error. I'd really appreciate it if someone could help me fix this problem!
public static void main(String[] args) {
//this allows the Py4J module in Python to use whichever methods it needs from this class
ExcelFileEditor editor = new ExcelFileEditor(new File(args[0]));
GatewayServer server = new GatewayServer(editor);
server.start();
}
The package is excel.writer
If you are not specifying where to place the generated class files then its going to be in the same directory as the source file.
Try
java -classpath C:\Users\rperera\IdeaProjects\LinkingNames\libs\*;C:\Users\rperera\IdeaProjects\LinkingNames\src excel.writer.ExcelFileEditor
I know this question has already been answered many times, but unfortunately I couldn't find the right answer to my questions.
below is my package structure and inside my package I have SimpleTest.java
d:\junit\src\junitfaq\SimpleTest.java
inside d:\junit\src> i tried to compile SimpleTest.java and it successfully compiled using the command below.
d:\junit\src>javac junitfaq/SimpleTest.java
but when i try to run the program using command line below
d:\junit\src>java junitfaq.SimpleTest
this error occured. Error: Could not find or load main class junitfaq.SimpleTest
I tried running it by accessing junitfaq package by using this command
d:\junit\src\junitfaq>java -cp . SimpleTest
the program run perfectly. A little help would be much appreciated.
Have you declared your SimpleTest class to be a member of the junitfaq package? If you have, you should be able to run it from the src directory like java junitfaq.SimpleTest but you should get an error like this if you try to run it from within the junitfaq directory: Exception in thread "main" java.lang.NoClassDefFoundError: SimpleTest (wrong name: junitfaq/SimpleTest)
Make sure your SimpleTest class starts with package junitfaq;
Edit: Here's a working example incorporating the comments below.
login#domain:~/temp> mkdir src
login#domain:~/temp> cd src
login#domain:~/temp/src> mkdir junitfaq
login#domain:~/temp/src> nano junitfaq/SimpleTest.java
The contents of SimpleTest.java are as follows when I exit nano:
package junitfaq;
public class SimpleTest {
public static void main(String[] args) {
System.out.println("Test");
}
}
login#domain:~/temp/src> javac junitfaq/SimpleTest.java
login#domain:~/temp/src> java junitfaq.SimpleTest
Test
It sounds like you have a classpath problem; you should double-check the location of your class file, the directory/package structure, the location from which you're trying to run the java command, and any classpath specified during execution.
For example, the following works for me:
$ mkdir junitfaq
$ cat >junitfaq/SimpleTest.java
package junitfaq;
public class SimpleTest
{
public static void main(String[] args)
{
System.out.println("Hello, world!");
}
}
^D
$ javac junitfaq/SimpleTest.java
$ java junitfaq.SimpleTest
Hello, world!
$ java -cp . junitfaq.SimpleTest
Hello, world!
$
Not to belabor the obvious, but I noticed a spelling typo in one of your comments - you should also double-check that you're running the command as intended.
trialYou could try putting your java and class files together with your libaray folder (if any) in a new file called "trial" in your C:\ directory then compile existing java file using the following->
C:\trial> javac -cp .;library folder* SimpleTest.java
(then)
C:\trial> java -cp .;library folder* SimpleTest
Let me know how you get on!
I was following this tutorial
here
and got a popup that says "cannot access class test"
after I typed in
%javac -g test.java
%ddd -jdb test &
When using DDD to debug java you must, as well as following the steps in the example you have provided, set the classpath that JDB uses to find your files. Otherwise you will see the message 'Cannot Access Class Test' that you are seeing.
To do this, in DDD click Edit, then JDB Settings, then type '.' (not including quote marks) in the classpath field. This will cause JDB to search in the current directory when looking for your example java code.
For more information about the java classpath and what it does, see
http://en.wikipedia.org/wiki/Classpath_%28Java%29
Hope this helps.
John
%javac -g test.java
%ddd -jdb test &
simple java program that works with these commands:
class test{
static public void Main(String[] args){
System.out.println("hello");
}
}