Difference between Iterator and List Iterator Example

/*

 *    Iterator traverse elements only in one direction i.e forward

 *    ListIterator traverse elements in both directions i.e forward and backward

 *    Using ListIterator we can modify the existing list as well as done in below sample

 */




public class IteratorClass extends Activity

{



ArrayList<String> miteratorList;

Iterator<String> mIterator;

ListIterator<String> mListIterator;



@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

initiViews();

}



private void initiViews()

{

//Initializing the ArrayList 

miteratorList=new ArrayList<String>();



//Adding values to the ArrayList

miteratorList.add("A");

miteratorList.add("B");

miteratorList.add("C");

miteratorList.add("D");

miteratorList.add("E");





//method to traverse elements using Iterator here

usingIterator();



//Initializing the mListIterator here

mListIterator=miteratorList.listIterator();



//method to traverse and modify elements using mListIterator here

usingListIterator();



//method to traverse elements using Iterator here

usingIterator();



usingListIteratorTOTraverseBackward();



}





private void usingIterator()

{

//Initializing the mIterator here

mIterator=miteratorList.iterator();//Returns an iterator on the elements of this list.

while(mIterator.hasNext())

{

Object element = mIterator.next();

System.out.print(element + " ");

}



//O/P goes like this => 04-29 18:32:44.590: I/System.out(26302): A B C D E



System.out.println();

}





private void usingListIterator()

{

//Modifying the existing list using list iterator

while (mListIterator.hasNext()) {

Object element=mListIterator.next();

mListIterator.set(element+"Z");  

}



System.out.println();



//04-29 18:45:44.588: I/System.out(1605): AZ BZ CZ DZ EZ



}





private void usingListIteratorTOTraverseBackward()

{

// Now, display the list in reverse order using ListIterator

      while(mListIterator.hasPrevious()) {

         Object element = mListIterator.previous();

         System.out.print(element + " ");

       }

       System.out.println();

      

          // 04-29 18:52:30.478: I/System.out(5954): EZ DZ CZ BZ AZ



}



}
 

 
 

Generating HMC SHA1 hash in Java Using a Secret Key (Private Key)

Below is the method :

void generateHMCSHA1(){



int counter= 1;

            String privateKey = "0123456789ABCDEF0123456789ABCDEF";

            byte[] result = null;

            MessageDigest md;

try {

md = MessageDigest.getInstance("SHA-1");

 byte[] keyBytes = md.digest(privateKey.getBytes("UTF-8"));



           SecretKey sk = new SecretKeySpec(keyBytes, "HmacSHA1");

           Mac mac = Mac.getInstance("HmacSHA1");

           mac.init(sk);

            result = mac.doFinal(String.valueOf(counter).getBytes("US_ASCII"));



           StringBuilder sb = new StringBuilder();

           for (byte b : result) {

               sb.append(String.format("%02X ", b));

           }

          

           System.out.println("      Key: " + privateKey + "\n");

       

           System.out.println("  Results: " +sb );

          

} catch (NoSuchAlgorithmException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (UnsupportedEncodingException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (InvalidKeyException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}           



}

Output :

Key: 0123456789ABCDEF0123456789ABCDEF
 
Results: 38 92 62 29 80 04 C9 83 EE 87 97 B0 C0 FD 77 4C 69 F3 82 

Program To Add Two Numbers In Java.

import java.util.Scanner; 

class AddNumbers
{
   public static void main(String args[])
   {
      int no1, no2, result;
      System.out.println("Enter two integers to calculate their sum ");
      Scanner in = new Scanner(System.in);
      no1 = in.nextInt();
      no2 = in.nextInt();
      result = no1 + no2;
      System.out.println("Sum of entered integers = "+result);
   }
}

Creating Package Using JAVA

package society;


public class Human
{
 public static void main(String arg[])
{
             Human t=new Human();
             t.hello();            


       }


    void hello()
  {
    System.out.println("hello");
  }


}

Use Of Scanner Class Function In JAVA

import java.util.Scanner;


public class Ar
{
   public static void main(String arg[])
 {
      int[] n=new int[10];
Scanner in=new Scanner(System.in);
System.out.println("Enter the elements : ");
      int i=0;

for(i=0;i<10;i++)
{
System.out.print("Enter the element a[ : "+ i +"] = ");
n[i]=in.nextInt();
}
for(i=0;i<10;i++)
{
System.out.println("elements are  a[ : "+ i +"] = "+n[i]);

}


   
 }
}

Coloring With JAVA

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Draw implements ActionListener
{
JFrame f;

JButton b1;
JButton b2;
JButton b3;
JLabel lb;
public Draw()
{
f=new JFrame();
b1=new JButton("RED");
b2=new JButton("GREEN");
b3=new JButton("ORANGE");
lb=new JLabel();

Shape s=new Shape();

b1.addActionListener(this);
b2.addActionListener(this);
b3.addActionListener(this);

f.add(BorderLayout.CENTER,s);
lb.setForeground(Color.white);
f.add(BorderLayout.NORTH,lb);
f.add(BorderLayout.SOUTH,b1);
f.add(BorderLayout.WEST,b2);
f.add(BorderLayout.EAST,b3);

f.setVisible(true);
f.setSize(400,400);
}
public void actionPerformed(ActionEvent ae)
{

}
public void paintComponent(Graphics g)
{
g.setColor(Color.red);
g.fillRect(20,30,110,110);
}
public static void main(String[] args)
{
Draw a=new Draw();
}


}