Javac编译和2个Java文件的执行

Question

The program is written with 2 files filter.java - in which is the main function and ClasifiedWord.java which is only container class. I wrote that on windows on eclipse but want to compile it on Linux javac compiler.

javac filter.java ClasifiedWord.java

runs without mistakes, but when I try to run the program:

snowy:Filter$ java filter 
Exception in thread "main" java.lang.NoClassDefFoundError: filter
Caused by: java.lang.ClassNotFoundException: filter
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: filter.  Program will exit.
snowy:Filter$ javac filter.java ClasifiedWord.java
snowy:Filter$ java filter ClasifiedWord
Exception in thread "main" java.lang.NoClassDefFoundError: filter
Caused by: java.lang.ClassNotFoundException: filter
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: filter.  Program will exit.

How can I run the program ? It seems that the compilation is ok. I have doubts that maybe I have made a mistake about the file paths in the program.... but I think that this is not the case? Thanks for your answers!

Answer 1

Type the following command.

java -classpath . filter

If you want to type just java filter , please following these guides.

• Linux http://www.cyberciti.biz/faq/linux-unix-set-java_home-path-variable/
• Windows http://ac-support.europe.umuc.edu/~arnoldyl/NetBeansTutorials/Setting-Classpath.html

PS The last command java filter ClasifiedWord means to run a program filter and use a string ClasifiedWord as an argument.

Answer 2

Roland is right in the comment, you should be able to run it with java -classpath <folderContainingDotClassFiles> filter . Also, you should change filter.java to Filter.java as the standard Java convention for class names (including the files containing them) is to capitalize the first letter.

Answer 3

This looks like you either have a wrong CLASSPATH setting (usually you don't need this at all, but if you have it, it should include . in the list, for the current directory), or you are using packages (wrongly), or both. For the classpath issue, see the other answers.

If you are using packages, ie your files contain a package ...; line at the beginning, you should put your source files in a directory structure according to the package structure. For example, if you have package example; , you should have an example directory in your current directory, and in this the two source files.

Then call compiler and interpreter like this:

javac example/filter.java example/ClasifiedWord.java
java example.filter

(This assumes that filter is the main class, otherwise replace its name.)