Can we define variables in interface in Java?

In Java , interface doesn't allow you to declare any instance variables. Using a variable declared in an interface as an instance variable will return a compile time error. You can declare a constant variable, using static final which is different from an instance variable.

How Java Lambdas Expressions affect the code in simple way

Let us start with some basic examples. Here, we will see how lambda expressions affect the code in a simple way. Having a list of players, the “for loop”, as programmers often refers to the for statement, can be translated in Java SE 8 as below:

String[] s1 = {"Anant", "Nilan", "Dolagobinda", "Babu", "Rupeli", "Sanjay", "Akshay", "Santosh"};

List<String> players =  Arrays.asList(s1);

      

// Old looping

for (String player : players) {

     System.out.print(player + "; ");

}

      

// Using lambda expression and functional operations

players.forEach((player) -> System.out.print(player + "; "));

// Using double colon operator in Java 8

players.forEach(System.out::println);

What is JAVA Lambda Expression???

Java Lambda expressions are a new and important feature included in Java SE 8. A lambda expression provides a way to represent one method interface using an expression. A lambda expression is like a method, it provides a list of formal parameters and a body (which can be an expression or a block of code) expressed in terms of those parameters.

Lambda expressions also improve the Collection libraries. Java SE 8 added two packages related to bulk data operations for Collections, the java.util.function package, and the java.util.stream. A stream is like an iterator, but with a lot of extra functionality. Taken together, lambda expressions and streams are the biggest change to Java programming since the generics and annotations were added to the language. 

How to sort ArrayList in JAVA

CollectionSort.java package java8s; import java.util.*; public class CollectionSort {           public static void main(String... args)           {                        List l = new ArrayList();                        l.add("Bhubaneswar");                        l.add("Cuttack");                        l.add("Paradeep");                        l.add("Jagatsinghpur");                        l.add("Kujanga");                        Collections.sort(l);                                                     System.out.println("Location : "+l);                                        } }

Output

Location : [Bhubaneswar, Cuttack, Jagatsinghpur, Kujanga, Paradeep]

How to avoid duplicate values from JAVA List / ArrayList

Hiii frnds, this is a nice question in interview forum, so let's see how to remove duplicate objects from List / ArrayList

ArrayListExample.java

package java8s;

import java.util.*;

public class ArrayListExample {

     public static void main(String[] args) {

          ArrayList al=new ArrayList();

          al.add("first");

          al.add("second");

          al.add("third");

          al.add("first");

          al.add("first");

         

          ArrayList al1=new ArrayList(new LinkedHashSet(al));

         

          Iterator it=al1.iterator();

          while(it.hasNext())

          {

              System.out.println(it.next());

          }

     }

}

Output

first

second

third

GET vs. POST in Servlet

	GET	POST
1.	It is used for getting information from the server side	It is used to post the information to the server.
2.	It performs read-only operation	It performs update/write operation.
3.	Whatever the request can be sent that is append with URL	Whatever request send to the server that is not exposed in the URL
4.	Only text or character type of data can be sent	Any type of data can be send
5.	Limited amount of data can be send (up to 2KB)	No length limit of data that we can send
6.	It provides less security because the user’s request is directly exposed in URL bar. Hence, sensitive  information is not recommended to be send.	It provides high security
7.	Bookmarking is possible which is the advantage	Bookmarking is not possible
8.	Caching is also possible which is also another advantage of get method	Caching is not possible

What is Composition in JAVA !!!

Composition is restricted form of agreegation. For example, a class car can't exist without engine.


class Car
{
  private Engine engine;
  Car(Engine en)
  {
    engine en;
  }
}

Why String[] args in main() method in JAVA?

The main objective is designed very intelligently by developers. Actual thinking is very deep. Which is basically developed under consideration of C & C++ based on Command line argument but nowadays nobody uses it more.

Thing 1- User can enter any type of data from the command line can be Number or String & necessary to accept it by the compiler which datatype we should have to use?

Thing 2- String is the datatype which supports all of the primitive datatypes like int, long, float, double, byte, shot, char in Java. You can easily parse it in any primitive datatype.

let's see the following example, 

If input is -> 1 1

// one class needs to have a main() method

public class HelloSilan

{

  // arguments are passed using the text field below this editor

  public static void main(String[] x)

  {   

System.out.println(x[0] + x[1]); // Output is 11

//Comment out below code in case of String

    System.out.println(Integer.parseInt(parameter[0]) + Integer.parseInt(parameter[1])); //Output is 2

    System.out.println(Float.parseFloat(parameter[0]) + Float.parseFloat(parameter[1])); //Output is 2.0   

    System.out.println(Long.parseLong(parameter[0]) + Long.parseLong(parameter[1])); //Output is 2   

    System.out.println(Double.parseDouble(parameter[0]) + Double.parseDouble(parameter[1])); //Output is 2.0   

  }

}

What is checked exception?

The exception which is checked by the compiler at the time of compilation for smooth execution of the program is known as checked exception.
Example:
import java.io.*;
class Test{
public static void main(String[] args){
PrintWriter pw=new PrintWriter("abc.txt");
pw.println("SILAN TECHNOLOGY");
}
}
sometimes the compiler check some specific program for smooth execution at run time, so when we compile this program we will get following compile time error :

unreported exception java.lang.FileNotFoundException must be caught or declared to be thrown

JDBC-Store image in Oracle Database

It is possible that we can store images in the database by executing jdbc program with the help of PreparedStatement interface.

The setBinaryStream() method of PreparedStatement is used to set Binary information into the parameterIndex.

For example:

CREATE TABLE user  

(

id varchar2(100),

name varchar2(100),

image BLOB

);  

Let's write the program to store the image in the database. Here we are using e:\\a.jpg for the location of image. You can change it according to the image location.

JDBC Example to store image in the database

import java.sql.*;  

import java.io.*;  

public class InsertImageDemo {  

public static void main(String[] args) throws Exception{  

Class.forName("oracle.jdbc.driver.OracleDriver");  

Connection con=DriverManager.getConnection(  

"jdbc:oracle:thin:@localhost:1521:xe","system","oracle");  

              

PreparedStatement ps=con.prepareStatement("insert into user values(?,?,?)");  

ps.setString(1,101);  

ps.setString(2,"Tapuuu");  

  

FileInputStream fin=new FileInputStream("e:\\a.jpg");  

ps.setBinaryStream(2,fin,fin.available());  

int k=ps.executeUpdate();  

System.out.println(k+" row inserted");  

          

con.close();  

}

}  

Output

1 row inserted

Note : If you see the table, record is stored in the database but image will not be shown. For this, you need to retrieve the image from the database.