Java Shell Commands: javac java jar javadoc
The purposes of these tools are:
javac→ compile Java source code.
java→ run Java program.
jar→ pack Java class files.
javadoc→ generate Java doc.
man javac to read its manual page.
Following are examples of using these commands.
Compile Java File
javac Aa.java → compile a source code file “Aa.java”. It will generate a file named “Aa.class”. That's the compiled file.
Note: by convention, Java class file name starts with capital letter.
Run Java File
java Aa → run the class file “Aa.class”, starting with the class's method named “main”. (Note: do not add the “.class” suffix in the command line.)
Note: Class name and its corresponding file name have a sameness relation enfored by Java. Each file has class, and the class name is the same as file name (without the “.class” suffix.)
〔►see Java: Package〕
java ff/Aa → run the class file “Aa.class” in directory “ff”.
Note: directory represents a package. A package name has a directory of the same name, and is enforced by Java. So, a package “hh” will be in directory “hh”, and a package “hh.ii” will be in directory “hh/ii”, etc. In the directory, are class files.
java -cp classpaths class_name → run the program class_name, and search classes in classpaths. The classpaths can be relative to the current dir, and multiple class paths are separated by colon :. By default, java search class files in current directory. (and also by environment variable CLASSPATH)
java -jar jar_file_path → run the jar file.
Classpath can contain both compiled java class file or jar file.
# run a java program # search class files in current directory and gg.jar # start program with package hh and class Jj java -cp .:gg.jar hh.Jj