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Types of package



              Types of package

Packages: Packages is a collection of classes. In java, there are two types of packages:

            1. Pre-defined packages
            2. User defined packages

1. Pre-defined packages: These packages come with the java library. Some of the packages are listed below:


Packages                                                                                             Description

(i) java.lang                                         This package is automatically imported. It contains the java classes which we normally use e.g. String,Integer,etc.

(ii) java.applet                                     This package will contain the classes related to the applet programming.

(iii) java.awt                                        This package contains the classes which will be helpful in creating the GUI components.

(iv) java.awt.event                               This package contains interfaces and classes for implementing and handling the events

(v) java.io                                            This package contains the classes related to   reading data from keyboard , and handling the stream. And also interacting with the files

(vi) java.net                                         This package contains the classes for the network and socket programming .

(vii) java.util                                        This package contains the classes for the common utilies program etc.. Calendar,                                                                                 Random etc..


2. User Defined packages:

In order to define your own package, we have to include the following statement as the first statement of your program

The statement is :
                                                            package packagename;

Consider the following program ,

package p;

class Sample
{
            int i,j;
            public void setij(int a,int b)
            {
                        i=a;
                        j=b;
            }
            public void show()
            {
                        System.out.println("i="+i);
                        System.out.println("j="+j);
            }
            public static void main(String args[ ])
            {
                        Sample ob=new Sample();
                        ob.setij(6,7);
                        ob.show();
            }
}

Step for executing the above program:
1. First create the folder with name p suppose in the d: drive, so the path will be d:\p
2. Now, save the file with the name Sample.java in the folder d:\p
3. Now, make the folder d:\p as your current directory.
            Move to dos,

                        run----> type command.com
                        The following prompt will appaer.
                        c:\windows\desktop>_
                        c:\windows\desktop>d:
                        d:\>cd p
                        d:\p>

4. Now, compile the program
                        d:\p>javac Sample.java

5. To execute, move to its parent directory
                        d:\p>cd..
                        d:\>java p.Sample
           
Multiple classes in the same package:
            In this case a single package contains the multiple classes. 

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