Java: javac java jar javadoc

By Xah Lee. Date: . Last updated: .

Purpose

javac

Compile Java source code.

java

Run Java program.

jar

Pack Java class files.

javadoc

Generate Java doc.

Type 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 generates a file named “Aa.class”. That's the compiled file.

💡 TIP: 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.

💡 TIP: do not add the “.class” suffix in the command line.

💡 TIP: 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”.

💡 TIP: directory represents a package. A package name has a directory of the same name, and is enforced.

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

jar files