JSP Interview Questions

1. How to create a Thread safe JSP page?
Ans: Theoretically, JSP pages can be indicated as threadsafe via the isThreadSafe page directive attribute

2. How to catch RunTimeException in JSP?

Ans: http://www.tutorialspoint.com/jsp/jsp_exception_handling.htm

2. What is the difference between request.getSession() and request.getSession(true)?

Ans: There is no difference at all.

3. Why we don't define constructor in servlets?

Ans: 1. HttpServlet is a dynamically loaded class so any argument can't be passed in the constructor.
2. Servlet is an interface, we can't define a constructor for that.

Multithreading example for producer consumer problem for alternate numbers

Problem Statement:

Write a multithreading program which uses 2 threads. One threads prints odd numbers and other prints even numbers. The final output should print the numbers in sequence.

Solution:

1. Main.Java

public class Main {
   
    public static void main(String [] args){
        Monitor m=new Monitor();
        Thread task1=new Thread(new Task1(m));
        Thread task2=new Thread(new Task2(m));
        task1.start();
        task2.start();
      
    }

}

2. Monitor.java

public class Monitor {
    private boolean flag=true;

    public boolean isFlag() {
        return flag;
    }

    public void setFlag(boolean flag) {
        this.flag = flag;
    }
   

}


3. Task1.java

public class Task1 implements Runnable{
    private Monitor monitor;
   
   
    public Task1(Monitor monitor) {
        super();
        this.monitor = monitor;
    }


    @Override
    public void run() {
        for(int i=0; i<=10; i=i+2){          
        synchronized (monitor) {
            while(!monitor.isFlag()){
                try {
                    monitor.wait();
                    } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        System.out.println("Printing :"+i);
        monitor.setFlag(false);
        monitor.notifyAll();

              
                }
        }
      
    }

}

Task2.java

public class Task2 implements Runnable{
    private Monitor monitor;
   
   
    public Task2(Monitor monitor) {
        super();
        this.monitor = monitor;
    }


    @Override
    public void run() {
        for(int i=1; i<=10; i=i+2){           
        synchronized (monitor) {
            while(monitor.isFlag()){
                try {
                    monitor.wait();
                    } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
               
            }
        System.out.println("Printing :"+i);
                monitor.setFlag(true);
                monitor.notifyAll();
        }
        }
       
    }

}