Problems running a java program from the command line interface

Question

I created a java program in Eclipse. When I run the program in Eclipse ("run as -> Java Application") the program runs fine and I have the correct output. However, when I try to run the program in the command line interface I got this error:

Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong name: helloworld/HelloWorld) Could not find the main class: HelloWorld. Program will exit.

The class file is in directory bin and I try to run it with the command:

java HelloWorld

Is your class in the default package (i.e. no package declaration)? And when saying `I try to compile it with the command: java HelloWorld`, did you mean running? — wjans, May 09 '11 at 09:41

score 1 · Answer 1 · answered May 09 '11 at 09:36

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I try to compile it with the command: java HelloWorld

TO compile a java program you should use javac command like

javac Helloworld.java

answered May 09 '11 at 09:36

Harry Joy

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I meant run the file not compiled it as it is already compiled. – Victor May 09 '11 at 09:43
@Victor: Are you providing all required jars in classpath when running it? – Harry Joy May 09 '11 at 09:48
I don't have jars file only the HelloWorld.class and the HelloWorld.java – Victor May 09 '11 at 09:51
@Vector: if your class have package declaration then you should set your class path upto the folder containing helloworld folder instead of helloworld folder. – Harry Joy May 09 '11 at 09:55
And how am I supposed to do that? – Victor May 09 '11 at 10:00
@Victor: by providing class path as -cp argument while running your program. – Harry Joy May 09 '11 at 10:03

score 1 · Answer 2 · answered May 09 '11 at 09:37

Are you sure that the directory where your classes are is in the classpath? Typically, in your project directory, the "classes" or "lib" directory.

If you are running from that directory, you could try adding ".".

See the -cp parameter of java runtime executable.

score 1 · Accepted Answer · answered May 09 '11 at 09:55

1

Since your class is in the package helloworld you should run it like this:

java helloworld.HelloWorld

Also make sure "." is on your classpath.

answered May 09 '11 at 09:55

wjans

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It worked. I had to typed it in the directory before the helloworld directory. – Victor May 09 '11 at 10:11

Problems running a java program from the command line interface

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