Skip to main content

Basic Java Interview Questions

1. Why java does not support multiple inheritance ?
Answer :- To say why java doesn't support inheritance directly like c++ should be the diamond problem faced by c++,(Diamond problem is an ambiguity that arises when two classes B and C inherit from A, and class D inherits from both B and C. If a method in D calls a method defined in A
(and does not override it), and B and C have overridden this method differently, then via which class does it inherit: B, or C?)


2. JVM crash is an Error or Exception.?
Answer:- JVM crash is an Error as a normal developer as we cannot handle it, but its exception for JVM developer as they can fix it.

3. Print “Hello World!” Without Main Method in Java?


Answer:-
public class Testing {
   static
   {
       System.out.println("Hello World");
   }
   public static void main(String[] args)
   {

   }
}

4. Collections in Java?
  1. Interfaces
  2. Iterable
  3. Collection
  4. Generic Collections
  5. List
  6. Set
  7. SortedSet
  8. NavigableSet
  9. Map
  10. SortedMap
  11. NavigableMap
  12. Queue
  13. Deque
  14. Stack
  15. hashCode() and equals()
  16. Sorting

5. Difference between Error and Exception?
Answer:- Error cannot be handle and Exceptions can be handle

6. Difference between Abstract Class and Interface?

7. Difference between Data Hiding and Data Encapsulation?

8. What type of Inheritance does JAVA support?

9. Abstract Class Live Example?

Comments

Popular posts from this blog

Uploading data on Remote Server in Java

This blog demonstrate how to upload data from file to remote server/database. Follow the steps as shown. 1. Create new Dynamic Web Project. 2. Now create all the packages as show in the image below. 3. Create controller with name ImportContact.java 4. Create pojo with name Contact.java 5. Create database layer code with name ImportContactBroker.java 6. Create connectivity with name DBConnection.java 7. Create db connectivity setting file as connectionSetting.java 8. Create jsp page with importcontact.jsp 9. Create supporting files like Constant.java and CsvReader.java 10. You can download the war file and import in your workspace. 11. MultipartRequest in Servlet and inside jsp helps to upload file on the remote server. 12. Download sample csv file from here . 13. Create Table with name Contact in Database as given in configuration file. 14.Just compile and run the code. ImportContact.java package com.uploadfile.controller; import java.io.BufferedReader; impo...

JOINs in MySQL

JOIN's is used to query data from two or more than two table based on relationship between certain columns in these tables. Tables in Database are related to each other with some constraints like (Primary Key & Foreign Key) Primary Key :- Column with unique value for each row that is not value matching to each other in the column. Foreign Key :- Two tables are mapped through concept of primary and foreign key, that means primary key of one table is used in other table as foreign key. fig : Primary Key and Foreign Key Example Query to create the above two tables. CREATE TABLE `project_mst` (   `PK_PROJECT_ID` varchar(10) NOT NULL,   `PROJECT_NAME` varchar(100) default NULL,   `PROJECT_DURATION` varchar(50) default NULL,   `FK_MANAGER_ID` varchar(10) default NULL,   PRIMARY KEY  (`PK_PROJECT_ID`) ) CREATE TABLE `manager_mst` (   `PK_MANAGER_ID` varchar(10) NOT NULL,   `MANAGER_...

Creating Pdf in multiple Languages in Java

Creating Pdf in multiple Languages in Java This code demonstrate how to create pdf in multiple languages in java by using ITEXT pdf creator. To use this sample code download itext.jar To display different locale on pdf you need to download font known as Arialuni.ttf and added to the project Most important thing is the encoding part set encoding to "Identity-H" (String encoding = "Identity-H";) as well as create font for the same to take effect in pdf create font (Font fontNormal = FontFactory.getFont(("c:/windows/fonts/arialuni.ttf"), encoding,BaseFont.EMBEDDED, 8, Font.NORMAL);) You can download the source code from here import java.io.FileOutputStream; import com.lowagie.text.Chunk; import com.lowagie.text.Document; import com.lowagie.text.Font; import com.lowagie.text.FontFactory; import com.lowagie.text.HeaderFooter; import com.lowagie.text.Paragraph; import com.lowagie.text.Phrase; import com.lowagie.text.pdf....