Organize your code with package and jar (Notes of reading Head First Java)

I'm reading 'Head First Java' recently and here are some notes about package and jar.

Jar usage

• Use jar file to compact your class files
• /projects/class contains all classes files
• /projects/source contains all java files
• create manifest.txt under class
• content of manifest.txt: 
• Main-Class: <main_class> // don’t put .class on the end
• Press the return key after typing the Main-Class line
• Create jar file
• cd /projects/class
• jar -cvmf manifest.txt <file_name>.jar *.class
• Execute jar file
• java -jar <file_name>.jar

Organize your code in packages

• Organize source code
• /projects/source/com/shunrang/ contains all java files
• Add this as the first line of all java files: package com.shunrang
• Compile source code
• mkdir /projects/class
• cd /projects/souce
• javac -d ../class com/shunrang/*.java
• Run your code
• cd /projects/class
• java com.shunrang.<main_class>
• The -d flag in javac will create the same structure under class folder as what is inside source folder

Combine Jar and package

• Create manifest.txt file
• Put manifest.txt under /projects/class
• Content of manifest.txt: Main-Class: com.shunrang.<main_class>
• Create Jar file
• cd /projects/class
• jar -cvmf manifest.txt <file_name>.jar com //All you specify is the com directory
• Run Jar file
• java -jar <file_name>.jar
• Useful jar command
• jar -tf <file_name>.jar //List the contents of a JAR, -tf stands for ‘Table File’
• jar -xf <file_name>.jar //Extract the contents of a JAR, -xf stands for ‘Extract File'