package در جاوا

• package is same as a folder that contains the related .class file.
• to create a package the keyword "package" is used.
• the classes in the package should be declared as a public.
• if you want to use this classes in another class outside the package then
  you have to import to that class using import keyword.
• using import keyword you can import a single or particular class or all
  the classes using * operator.
• the * operator imports only classes present in that package. not the sub packages.
• to compile a class that contains a package we use "javac -d . programname.java"
• "-d" describe to create the directory. "." describes the part of directories same where the file is stored.
• the package statement should be the first statement in the program and only
  one package statement can be written inside a program whereas n number of
  import statement we can write.
• if class is not public we can not use it outside the package.