Skip to main content

Q) Key points about Inheritance implementation in java?





A)
->java doesn’t support multiple inheritance.
->super classes are generalized classes. Whereas sub classes are specialized classed.
->the bottom most classes in the hierarchy contain more specialized and the top most classes in the hierarchy contains more generalization.
->super class reference can refer to subclass object.
->As java supports single inheritance. It also supports two special cases of single inheritance
1. Multilevel inheritance.
2. Hierarchical inheritance.
->if a super class has more than one sub classes, it is known as hierarchical inheritance.
                               
                              
Hierarchical inheritance
->if a sub c lass is acting as a super class for another sub class, that form of inheritance is known as multilevel inheritance.
                               
                                              
-> Java.long.Object class is super class of all java classes.
-> Sub class objects substitute super class object in the application.
->inheritance provides reusability of code.
Security provided by encapsulation

Comments

Post a Comment

Popular posts from this blog

Q) Explain repeated deletion of records.

A) //RepeatedDeletion.java import java.util.Scanner; import java.sql.*; class RepeatedDeletion {        public static void main(String[] args) {               Connection con= DriverManager. getConnection ( "jdbc:odbc:prince" , "scott" , "tiger" );               PreparedStatement ps=con.PreparedStatement( "DELETE FROM ACCOUNT WHERE ACCNO=?" );               Scanner s= new Scanner(System. in );               while ( true )               {                      System. out .println( "Enter accno : " );      ...
Post a Comment
Read more

Q) Retrieving data from database?

A)   ->to retrieve the data from database we need to submit SELECT statement from JDBC application. -> executeQuery() method of statement object is used for this purpose. This method has the fallowing ResultSet executeQuery(String sql) throws SQLException Ex: ResultSet rs = st.executeQuery(“SELECT * FROM ACCOUNT”); ->objectoriented representation of tables formate data is called ResultSet object. Ao the driver created one object i.e. ResultSet object. ->object orientation representation of a table of records returned from db is nothing but “ ResultSet ” object.  
Post a Comment
Read more

Q) What is the purpose of JDBC?

A) -> Java application can do any task by making a method (function) call. ->java method calls are not understandable to database management system. They can understand only SQL statements. ->SQL statements can’t be directly used in a java application. Java compiler complains. ->therefore, we say that java environment and database environment are heterogeneous to each other. Purpose of JDBC: ->for any kind of java application to communicate with any kind of database (management system) in a standard manner, JDBC is used.
Post a Comment
Read more