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package creation in java example create packages in java user defined packages in java user defined packages in java example create user defined package java example create user defined package java creating packages in java creating packages in java with example create pacakages in java creating package in java steps for creating package in java creating a package in java creating a package in java with example
create a package in java with example steps for creating user defined package in java
User Defined
Packages :
Definition Of User Defined Package :
User defined
packages are those which are developed by java programmer and supplied
as a
part of their project to deal common specific requirements.
If we want to
give any class name or interface name to many number of java programmer
then
such type of classes and interfaces must be placed in a packages. In other
words the
package classes and interfaces must be placed in a package’s. In
other words the
packages classes and interfaces must be placed in a package. In
other words the package
classes and interfaces are meant for common access.
What are all
classes the guide lines are followed by sun micro system for development
of pre
defined packages, same guidelines will be followed by us for development of
user
defined packages.
Creating a user
defined package is nothing but creating those package names as directory /
folders in the current working machine.
For Example : java.awt.event.*;
In the above
package, java is one of the root of the root directory, awtis one of the sub
directory in java directory and event is sub directory in awt directory.
Java is sub
directory in the current working machines of sun micro system. Similarly p1.p2.p3.*; in the statement p1 is called
directory, p2 is sub directory and p3 is called sub – sub directory in our
current working machine.
Syntax for
creating package:
Package
pack1[pack2[pack3…….[pack n]]];
In the above
syntax
1)
Package is keyword used for developing user
defined package.
2)
Pack1, pack2……pack n represents java valid
variable names and they are treated
as name of user defined packages.
3)
Pack2, pack3……pack n represents name of the sub
packages and whose
specification is optional.
4)
Pack1 represents an upper package or outer
package and whose specifications is
mandatory.
For
Example :
Package p1;
or
Package p1,p2;
Guide lines
or steps for development of user defined package:
Sun micro system
has prescribed the following guidelines for development of user defined
packages.
1)
Choose an appropriate package for placing the
common classes and interfaces and
ensure that the package statement must be the
first executable statement.
2)
Choose an
appropriate class name / interface name and ensure that whose modifier
must be
public.
3)
The modifier of the constructor of the class
which is present in the package must be
public.
4)
The modifier of the method of class / interface
must be public (this rule is optional in the
case of interface’s_ because every
method of interface is public.
5)
Whichever class name / interface name present in
the package, the class name/ interface
name must be given as file name an
extension (.java).
6)
At any point either we need to write a class
definition or interface definition in the
package, but not both the definition
in the single window in the same package.
// Create a package pack1 and
place class called Demo
Package pack1;
Public class Demo
{
Public Demo()
{
System.out.println(“user defined package”);
}
Public void display()
{
System.out.println(“user defined
display method”);
}
}
Package pack1;
Public interface Test
{
Public void show();
}
Compiling package classes and
interface.
For Compiling package classes and
interfaces, we use the following
java –d . Demo.java
Then we can find under Pack1 package Demo.class and Test.class as follows
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