Skip to main content

Q) What are the difference between static variables and instance variables?




A)
No
                      Static variables
No
                   Instance variables
1
Per class only one copy irrespective of number of  objects
1
Per object one separate copy
2
It is used to represent entire class information but not individual object information
2
Meant for representing individual object information
3
Doesn’t contribute to the size of object
3
Contribute to the size of the object
4
Shared by each object and manipulated by the behaviour of the object
4
Owned by one object
5
Comes into existence as soon as the class is loaded and before any object is created
5
Comes into existence only when object is created
6
memory is deallocated when class is unloaded
6
memory is deallodated only when the object is garbage collected
7
Both static and instance method can access them
7
Only instance methods can access them  and static methods can’t refer them
8
Can refer both of them with class name and object name
8
Can’t refer them with class

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