Define a class named Document that contains an instance variable of type String named text that stores any textual content for the document. Create a method named toString that returns the text field and include a method to set this value. Next, define a class for Email that is derived from Document and includes instance variables for the sender, recipient, and title of an email message. Implement appropriate set and get methods. The body of the email message should be stored in the inherited variable text. Redefine the toString method to concatenate all text fields. Similarly, define a class for File that is derived from Document and includes an instance variable for the pathname. The textual contents of the file should be stored in the inherited variable text. Redefine the toString method to concatenate all text fields. Finally, define a class DocumentTest that creates each two sample objects of type Email and File in the main() method. Test your objects by passing them to the following function that returns true if the object contains the specified keyword in the text property. public static boolean ContainsKeyword(Document docObject, String keyword) { if (docObject.toString().indexOf(keyword,0) >= 0) return true ; return false; }  (Java)

Define a class named Document that contains an instance variable of type String named
text that stores any textual content for the document. Create a method named toString that
returns the text field and include a method to set this value.
Next, define a class for Email that is derived from Document and includes instance
variables for the sender, recipient, and title of an email message. Implement appropriate
set and get methods. The body of the email message should be stored in the inherited
variable text. Redefine the toString method to concatenate all text fields.
Similarly, define a class for File that is derived from Document and includes an instance
variable for the pathname. The textual contents of the file should be stored in the
inherited variable text. Redefine the toString method to concatenate all text fields.
Finally, define a class DocumentTest that creates each two sample objects of type Email
and File in the main() method. Test your objects by passing them to the following
function that returns true if the object contains the specified keyword in the text property.
public static boolean ContainsKeyword(Document docObject, String keyword)
{
if (docObject.toString().indexOf(keyword,0) >= 0) return true ;
return false;
}  (Java)