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A package in Java can be defined as a directory which contains a group of Java class files. The main advantage of this method is that any no. of derived classes can be created within the same package.
Below is a program which uses packages to show the details of an employee.
Package 1: Office
In the office directory there are two Java files - emp.java & dept.java
emp.java
package office;
public class emp
{
public String name,address,acc_no;
public emp(String nm,String add,String acc_no2)
{
name=nm;
address=add;
acc_no=acc_no2;
}
}
dept.java
package office; /* no need to use import within the same package */
public class dept extends emp
{
public String dept,desig;
public dept(String nm,String add,String acc,String deptm,String desg)
{
super(nm,add,acc);
dept=deptm;
desig=desg;
}
}
It is advisable to keep the code within the directory as when you compile it the class files will also be in the same directory.
To create the class use the following the commands :
javac emp.java
javac dept.java
If you face any problem while implementing the above command, you can also use the commands below :
javac office/emp.java
javac office/dept.java
Now, you have successfully created your first package.
Package 2 : Finance
In the finance package, there is a single java file - salary2.java
salary2.java
package finance;
import office.emp; /*use import to create derived class of outside
package */
import office.dept;
public class salary2 extends dept
{
private float basic,hr,da,saly;
public salary2(String nm,String add,String acc,String deptm,String
desg,float bas,float h_r,float d_a)
{
super(nm,add,acc,deptm,desg);
basic=bas;
hr=h_r;
da=d_a;
saly=basic + (float)0.01*hr + (float)0.01*da;
}
public void display()
{
System.out.println("Name : " + name);
System.out.println("Address : " + address);
System.out.println("Acc No. : " + acc_no);
System.out.println("Department : " + dept);
System.out.println("Designation : " + desig);
System.out.println("Basic Pay : " + basic);
System.out.println("DA : " + hr + "%");
System.out.println("HR : " + da + "%");
System.out.println("Total Salary : "+ saly);
}
}
Now to create the class files use the following commands :
javac salary2.java or javac finance/salary2.java
Now create a normal java outside of both the office and finance directory from where you can call the methods to show the details of the employees.
abc.java
import finance.salary2;
public class abc
{
public static void main(String args[])
{
salary2 sal=new salary2("Rohit","265,G.C.Road,Kolkata-
02","97832","SALES","CEO",8000,8,10);
sal.display();
}
}
Now the run the following commands to get the final output.
javac abc.java
java abc
The following output will be shown :
Name : Rohit
Address : 265,G.C.Road,Kolkata-02
Acc No. : 97832
Department : SALES
Designation : CEO
Basic Pay : 8000.0
DA : 8.0%
HR : 10.0%
Total Salary : 8000.18
Note : To create a derived class in the same package you don't need to use the import statement. You will need the import statement only when creating a derived class of an outside package.
This program is a simple illustration of creating packages in Java and derived classes within the same package.
