Java Servlets Part 3

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Java Servlet part 3 from Er Gurpreet singh

 

Java Servlets Part 2

Java Servlets Part 2 from Er Gurpreet singh

Java Servlets Part 1

Java Servlets Part 1 from Er Gurpreet singh

Which Non Access Modifier can be used which Non Access Modifier?

In Nutshell:

• abstract cannot be used with any other Non Access Modifier
• final can be used with all other Non Access Modifier except abstract
• synchronized can be used with all other Non Access Modifier except abstract
• native can be used with all other Non Access Modifier except abstract, strictfp
• strictfp can be used with all other Non Access Modifier except abstract, native
• static can be with all other Non Access Modifier except abstract

How to use Comparator in java?

import java.util.*;

class ComparatorTest {
    public static void main(String[] args) {
        List list = new ArrayList<>();
        list.add(new Employee("B", 3));
        list.add(new Employee("A", 1));
        list.add(new Employee("C", 2));

        Collections.sort(list, new EmployeeComparator());
        for (Employee emp : list) {
            System.out.println(emp.name + "\t" + emp.age);
        }
    }
}

class EmployeeComparator implements Comparator<Employee> {
    @Override
    public int compare(Employee o1, Employee o2) {
        if (o1.age > o2.age) {
            return -1;
        } else {
            return 1;
        }
    }
}

class Employee {
    String name;
    int age;

    public Employee(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

Output:

B 3
C 2
A 1

Applet Demo 1

Source Code:

import java.applet.*;
import java.awt.*;


public class Demo1 extends Applet
{
    public void init()
    {
        //Code to run automatically
        this.setSize(500, 500);
        this.setBackground(Color.CYAN);
    }
    public void paint(Graphics g)
    {
        
        
        //now draw graphics
        g.drawLine(0, 0, 100, 100);
        g.drawRect(0, 0, 100, 100);
        
        //change color of graphics
        g.setColor(Color.blue);
        g.drawString("Applet Demo", 0, 120);
    }
}

Getting Started with Java GUI Programming

Download the Netbeans IDE from filehippo.com/download_netbeans

Also download Java JDK(32-bit or 64-bit) according to your operating system. For 32-bit operating system download the 32-bit version of Java JDK and for 64-bit operating system download the 64-bit version of Java JDK

After downloading firstly install Java JDK and then Netbeans

Learn Java Part 11

Java ppt11 from Gurpreet singh

for each loop in java

What is for each loop?

for each loop in java is the enhanced version of for loop. It is introduced from JDK 5. It is used to iterate all elements of an array or Collection.

---

Syntax:



for ( data-type variableName :  array or collection )

{

    //statements

}

---

Consider the following program:

public class ForEachLoop
{
    public static void main(String[] args)
    {
        int[] array ={ 1, 2, 3, 4, 5 };
        System.out.println("Array elements: ");

        for(int element: array)
               System.out.print(element+"  ");

    }
}

Write the above program in Notepad and save it as ForEachLoop.java 

Compile and run it to get the following output:



Array elements: 

1  2  3  4  5



the loop for(int element: array)

fetches the elements of array and assign it to variable element so we can use element to access the elements of array



Consider the following program to access elements of multi-dimensional array

public class ForEachLoop
{
    public static void main(String[] args)
    {
     int[][] array ={ {1, 2, 3, 4,},{ 5,6,7,8} }; //array with 2 rows and 4 columns
        System.out.println("Array elements: ");
        for(int[] row: array)
            for(int element: row)
               System.out.print(element+"  ");
    }
}

Write the above program in Notepad and save it as ForEachLoop.java 

Compile and run it to get the following output:



Array elements: 

1  2  3  4  5  6  7  8



the loop for(int[ ] row: array)

fetches one row of array and assign it to variable row so we can use row to access one row(or one dimensional array) of array



the loop for(int element: row)

fetches the elements of row and assign it to variable element so we can use element to access the elements of row

Command Line Arguments

public class CommandLineArguments
{
    public static void main(String[] args)
    {
        System.out.println("Total number of Command Line Arguments: "+args.length);
        System.out.println("Command Line Arguments:");
        for(int i=0;i<args.length;i++)
            System.out.println(args[i]);
    }
}

Type the above program in Notepad and Save it as CommandLineArguments.java

Compile like this:



javac  CommandLineArguments.java



Run like this:



java  CommandLineArguments   Arguments



For example: 

---

java  CommandLineArguments   Hello World

output:



Total number of Command Line Arguments: 2

Command Line Arguments:

Hello

World

---

If you run like this:

java  CommandLineArguments

output:



Total number of Command Line Arguments: 0

Command Line Arguments:

---

Note: Each argument in command line arguments is seperated by a space

Learn Java Part 10

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Learn Java Part 10 from Gurpreet singh