Skip to main content

Q) what is the output of the program?


class constructorone
{
       constructorone(int a)
       {
              System.out.println("constructor of super class");
       }
}
class constructorone2 extends constructorone
{
       constructorone2()
       {
//super();->this method is written by compiler in compile time. For non parameterized constructor

              System.out.println("constructor of sub class");
       }
}
class constructoroutput4 {
       public static void main(String[] args) {
              constructorone2 b = new constructorone2();

       }

}
A)
Output :

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
       Implicit super constructor constructorone() is undefined. Must explicitly invoke another constructor

       at constructorone2.<init>(constructoroutput4.java:10)
at constructoroutput4.main(constructoroutput4.java:17)


Reason:
The above program causes compilation error as there is no zero argument constructor in super class.
Explanation:
Super class object is created in compile time. super() method is written in super class constructor method as first statement. That’s why the super class doesn’t contain zero argument constructor so that’s why error is raised.

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