A derived class is a Java class that inherits properties from its super class. For example, an
Employee class might be derived from a
Person class. Therefore the
Employee class could inherit first name and last name properties from
Person, its super class. The following eight steps show how to write a derived class in Java.
- Open your text editor and type in the following Java statements:
The program defines one property:
fullName. This property will contain first name and last name. Notice that the program follows the Javabean specification for defining a property, i.e., a private variable with getter and setter methods.
- Save your file as Person.java.
- Open a command prompt and navigate to the directory containing your Java program. Then type in the command to compile the source and hit Enter.
- Create a new file in your text editor. Type in the following Java statements:
Employeeclass defines one property:
empId. This property will contain the employee ID. Notice that the constructor calls the constructor in the super class (
Person). The full name parameter is passed to the constructor.
- Save your file as Employee.java.
- Return to the command prompt, then type in the command to compile the source and hit Enter.
- Create an application to test your derived class. Create a new file in your text editor and type in the following Java statements:
The program instantiates an Employee object and then calls the
getFullNamemethod. This method is located in the
Personclass. The method can be called from the Employee object, verifying that derived classes inherit super class methods.
- You will now test your program. Type in the command to run the Java runtime launcher and hit Enter. Notice the output of the program verifies that a method in the super class can be called using the derived class.