Info-Grade

Write a Java program to create Rectangle class with data member length and breadth. Include methods getData() and displayArea() in the class. Finally create an object of Rectangle class and display its area.

 

import java.util.Scanner; 
class Rectangle4{
	int l, b; 
	void getData(){
		Scanner in = new Scanner(System.in); 
		System.out.print("Enter length : "); 
		l=in.nextInt(); 

		System.out.print("Enter breadth : "); 
		b=in.nextInt(); 
	}

	void displayArea(){
		int a; 
		a = l*b; 
		System.out.println("Area = "+a); 
	}

	public static void main(String args[]){
		Rectangle4 obj = new Rectangle4();
		obj.getData(); 
		obj.displayArea();  
	}
}

Define the term class and object? How can you create class and object in Java? Explain with example.

Class is a blueprint to template of real world objects that specifies what data and what methods will be included in object of the class. Class is also called description group of object objects having similar properties. A class is also called user defined data type or programmers defined data type because we can define new data types according to our need by using classes.

Objects are instances of class. We can say that object is variable of class type. Memory for instance declaration rather at the time of class declaration rather than time of object creation. Thus we can say that objects have physical existence and classes are only concepts.

Declaring Classes
Syntax:
[Access Modifier] className{
// body
}

Creating Object
Syntax:
[className] [objectName] = new [className]();

Program

 
class Demo{
 void display(){
  System.out.println("Class Example");
 }
 public static void main(String args[]){
  Demo obj = new Demo(); 
  obj.display(); 
 }
}

What do you mean by JSP? Write a program in the JSP to display Message "I Love Programming" 100 times.

JSP is a Java Server side technology that does all the processing at server. It is used for creating dynamic web application using Java as programming language.

JSP Program to print "I Love Programming" 100 times.

Program

 
<!DOCTYPE html>
<html> 
<head> 
 <meta http-equiv="Content-Type" content="text/html" charset=UTF-8">
 <title> A simple JSP program </title> 
</head> 
<body> 
 <h1> Displaying "I love Programming 100 times !!" </h1> 
 <table> 
  <% for(int i=1; i<=100; i++){ %> 
   <tr> <td> I Love Programming </td> </tr> 
  <% } %>
 </table> 
</body> 
</html>

Write a program using swing components to find simple interest. Use text fields for input and output. Your program should display the result when the user presses a button.

Output of the given Java program

Program

 

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;       

class PTR extends JFrame implements ActionListener //implement listener interface
{
 JTextField t1, t2, t3, t4;
 JLabel l1,l2,l3, l4;
 JButton b1; 
 public PTR() 
 {
  super("Handling Action Event");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  
        l1 = new JLabel("Enter P :");
  l2 = new JLabel("Enter T :");
  l3 = new JLabel("Enter R : ");
  l4 = new JLabel("Interest : ");
  t1 = new JTextField(10);
  t2 = new JTextField(10);
  t3 = new JTextField(10);
  t4 = new JTextField(10); 
  b1 = new JButton("Calculate");
  
  setLayout(new FlowLayout(FlowLayout.LEFT,150,10));
        add(l1);
  add(t1);
  add(l2);
  add(t2);
  add(l3);
  add(t3);
  add(l4);
  add(t4); 
  add(b1);

  b1.addActionListener(this);//Registering event

  setSize(400,300);
        setVisible(true);
 }
 
 public void actionPerformed(ActionEvent ae) //Handle Event
 {
  int p, t, r, si; 
  p = Integer.parseInt(t1.getText());   
  t = Integer.parseInt(t2.getText()); 
  r = Integer.parseInt(t3.getText());
  if(ae.getSource() == b1)
   si = (p*t*r)/100;
  else
   si = 0; 

  t4.setText(String.valueOf(si));
 }

 public static void main(String a [])
 {
  new PTR();
 }
}

How array can be declared in Java? Write a complete Java program to read two numbers from the user (where first number is less then second number) then find only even number between them.

Array is a data structure which contains of similar data type. We store only fixed set of elements in a java array. Array is used to store a collection of data, but it is often more useful to think of an array as a collection of variable of the same type.

To declare an array in a Java program, we must declare a variable to reference the array and we most specify the type of array the variable can reference.
Syntax:
dataType[] arrayRefVar;
or
dataType arrayRefVar[];

Program

 

import java.util.Scanner; 
class EvenArray{
     public static void main(String args[]){
 Scanner in = new Scanner(System.in); 
 int x, y; 
 System.out.print("Enter First Number : "); 
 x = in.nextInt(); 
 System.out.print("Enter Second Number : "); 
 y = in.nextInt(); 

 for(int i=x; i<=y; i++){
      if(i%2==0){
     System.out.println(i); 
      }
 }
     }
}

What is thread in Java? Difference between process and thread? Life cycle of thread.

The thread is a lightweight process that means one single program can be divided into small threads which will execute concurrently for fast execution of task. We can say that thread is a sub process of a process.

A thread is an independent path of execution within a program. Many thread can run concurrently within a program. Every threads in Java is created and controlled by the java.lang thread class. A java program can have many threads, and these threads can run currently, either synchronously or asynchronously.

- Threads are lightweight compared to process.

Difference between thread and process

Process	Thread
- A Process is an instance of a program. It contains a threads.	- Threads are the parts of process. It cannot contain a process.
- Process run in its separate.	- Thread run in shared memory spaces.
- Process is controlled by the operating system.	- Threads a re controlled by programmer in a program.
- Processes are independent.	- Threads are dependent.
- New processes require duplication of the parent process.	- New threads are easily created.
- Process require more time for context switching as they are more heavy.	- Threads require less time for context switching as they are lighter then process.
- Process require more resources then threads.	- Threads generally need less resources than process.
- Process require more time for termination.	- Threads require less time for termination.

Life cycle of threads

New
The thread is in new state if you create an instance of thread class but before the invocation of start() method.

Runnable
A thread in the runnable state is executing the Java virtual machine but it may be waiting for other resources from the operating system such as processor.

Running
The thread is in running state if the thread scheduler has selected it.

Blocked (Non Runnable)
It is the state when the thread is still alive, but is currently not eligible to run.

Terminated
A thread is in terminated or dead state when its run() method exists.