# Java Tutorials

## Java Program to convert Decimal values to Hexadecimal values

Objectives :

• How to convert Decimal to Hexadecimal in Java?

### Java Program to convert Decimal values to Hexadecimal values :

[sourcecode lang=”java”]

import java.util.Scanner;

public static void main(String[] args) {

Scanner input = new Scanner(System.in);

System.out.print("Enter decimal number you like: ");
int deci = input.nextInt();

System.out.println("The hexadecimal number for decimal "
+ deci + " is " + convert(deci));
}

public static String convert(int decimal) {
String hex = "";

while (decimal != 0) {
int hexValue = decimal % 16;
decimal = decimal / 16;
}

return hex;
}

public static char toHexadecimal(int hexValue) {
if (hexValue <= 9 && hexValue >= 0) {
return (char) (hexValue + ‘0’);
} else {
return (char) (hexValue – 10 + ‘A’);
}
}
}

[/sourcecode]

Output :
Enter decimal number you like: 1234
The hexadecimal number for decimal 1234 is 4D2

## Java Program to Convert Decimal Number to Roman Number

Objectives :

• Convert Decimal number to Roman number
• Convert Decimal numeral to Roman numeral
• How to convert a decimal number to roman number
• Write a program that converts a decimal number to Roman number.
• Write a program that converts a decimal number to Roman number. Decimal Number is accepted using Scanner class at the time of execution.
• Write a program that converts a decimal number to Roman number. Decimal Number is accepted as command line input at the time of execution.

Program :

### Java program that converts a decimal number to Roman number. Decimal Number is accepted using Scanner class at the time of execution.

[sourcecode lang=”java”]

&nbsp;

import java.util.Scanner;

public class DecimalToRoman {

private static String toRoman(int num) {
String[] romanCharacters = { "M", "CM", "D", "C", "XC", "L", "X", "IX", "V", "I" };
int[] romanValues = { 1000, 900, 500, 100, 90, 50, 10, 9, 5, 1 };
String result = "";

for (int i = 0; i < romanValues.length; i++) {
int numberInPlace = num / romanValues[i];
if (numberInPlace == 0) continue;
result += numberInPlace == 4 && i > 0? romanCharacters[i] + romanCharacters[i – 1]:
new String(new char[numberInPlace]).replace("\0",romanCharacters[i]);
num = num % romanValues[i];
}
return result;
}

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a number : ");
int decimal = scanner.nextInt();
System.out.println(toRoman(decimal));
}

}

[/sourcecode]

Output :

Enter a number : 1234

MCCXXXIV

### Java program that converts a decimal number to Roman number. Decimal Number is accepted as command line input at the time of execution.

[sourcecode lang=”java”]

public class DecimalToRoman {

private static String toRoman(int num) {
String[] romanCharacters = { "M", "CM", "D", "C", "XC", "L", "X", "IX", "V", "I" };
int[] romanValues = { 1000, 900, 500, 100, 90, 50, 10, 9, 5, 1 };
String result = "";

for (int i = 0; i < romanValues.length; i++) {
int numberInPlace = num / romanValues[i];
if (numberInPlace == 0) continue;
result += numberInPlace == 4 && i > 0? romanCharacters[i] + romanCharacters[i – 1]:
new String(new char[numberInPlace]).replace("\0",romanCharacters[i]);
num = num % romanValues[i];
}
return result;
}

public static void main(String[] args) {
if(args.length<1 || args.length>1){
System.out.println("Wrong input");
}else{
String number = args[0];
int decimal = Integer.parseInt(number);
System.out.println(toRoman(decimal));
}
}

}

[/sourcecode]

## Passing data between activities in Android

Objective :

• Passing data between activities in Android
• Passing multiple data between activities in Android
• Passing array between activities in Android
• Passing ArrayList between activities in Android
• Passing ArrayList to another activity in Android
• Sending data via Intent in Android
• Sending multiple data via Intent in Android
• Sending array between activities in Android
• Sending ArrayList between activities in Android
• Sending ArrayList to another activity in Android
• Sending data via Intent and Bundle in Android
• Sending multiple data via Intent and Bundle in Android
• Passing array between activities in Android using Intent and Bundle
• How to pass array to another activity in Android?
• How to pass array between activities in Android?
• How to pass data to another activity in Android?
• How to pass data to activity in Android?
• How to pass data to between activities in Android?
• How to pass ArrayList to another activity in Android?
• How to pass ArrayList between activities in Android?

## Code for passing data between activities in Android :

ActivityOne.java

[sourcecode lang=”java”]

String value = "Hello!";
Intent in = new Intent(this,ActivityTwo.class);
in.putExtra("Key", value);
startActivity(in);

[/sourcecode]

ActivityTwo.java

[sourcecode lang=”java”]

Bundle bundle = getIntent().getExtras();

[/sourcecode]

## Code for passing multiple data or values between activities in Android :

### Method 1 : Using Intent to pass data and Bundle to extract data between activities in Android

ActivityOne.java

[sourcecode lang=”java”]

String value1 = "Hello!";
String value2 = "Hi!";
Intent in = new Intent(this,ActivityTwo.class);
in.putExtra("Key1", value1);
in.putExtra("Key2", value2);
startActivity(in);
[/sourcecode]

ActivityTwo.java

[sourcecode lang=”java”]
Bundle bundle = getIntent().getExtras();
[/sourcecode]

### Method 2 : Using Bundle to pass and to extract data between activities in Android

ActivityOne.java

[sourcecode lang=”java”]

String value1 = "Hello!";
String value2 = "Hi!";
Intent in = new Intent(this,ActivityTwo.class);
Bundle bundle = new Bundle();
bundle.putString("Key1", value1);
bundle.putString("Key2", value2);
in.putExtras(bundle);
startActivity(in);
[/sourcecode]

ActivityTwo.java

[sourcecode lang=”java”]
Bundle bundle = getIntent().getExtras();
[/sourcecode]

## Code for passing array between activities in Android :

ActivityOne.java

[sourcecode lang=”java”]
String[] array = new String[]{"Item1", "Item2", "item3", "Item4", "item5"};
Intent in = new Intent(this,ActivityTwo.class);
Bundle bundle = new Bundle();
bundle.putStringArray("MyArray", array);
in.putExtras(bundle);
startActivity(in);
[/sourcecode]

ActivityTwo.java

[sourcecode lang=”java”]
Bundle bundle = getIntent().getExtras();
[/sourcecode]

## Code for passing ArrayList between activities in Android :

ActivityOne.java

[sourcecode lang=”java”]
ArrayList<String> array = new ArrayList<String>();
Intent intent = new Intent(this, ActivityTwo.class);
intent.putExtra("array_list", array);
startActivity(intent);
[/sourcecode]

ActivityTwo.java

[sourcecode lang=”java”]
Bundle bundle = getIntent().getExtras();
ArrayList<String> array = (ArrayList<String>) bundle.getStringArrayList("array_list");
[/sourcecode]

Have fun with Intent.

## Java Program to Convert Binary to Decimal

Objectives :

• Binary to Decimal Conversion
• Converting Binary to Decimal
• Write a program to convert binary to decimal
• Write a program to convert binary number to decimal format
• Write a program to convert binary to decimal using Scanner class
• Write a program to convert binary to decimal, take input using Scanner class

Java Program :

[sourcecode lang=”java”]

import java.util.Scanner;

public class BinaryToDecimal {

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print(&quot;Enter binary number: &quot;);
String binary = scanner.nextLine();
int decimal = binaryToDecimal(binary);
System.out.println(&quot;Decimal equivalent of &quot;+ binary +&quot; is &quot;+ decimal);
}

private static int binaryToDecimal(String binary) {
final int base = 2;
int decimal = 0;
for (int i = 0; i &lt; binary.length(); i++) {
if (binary.charAt(i) == ‘0’) {
decimal += 0 * Math.pow(base, binary.length() – i – 1);
} else if (binary.charAt(i) == ‘1’) {
decimal += 1 * Math.pow(base, binary.length() – i – 1);
} else {
System.out.println(&quot;Invalid Binary Number&quot;);
System.out.println(&quot;Binary Number Contains only 0’s or 1’s&quot;);
System.exit(0);
}
}
return decimal;
}
}

[/sourcecode]

Output :
Enter binary number: 1110
Decimal equivalent of 1110 is 14

## Java Program to convert Decimal to Binary

Objectives :

• Decimal to Binary Conversion
• Converting Decimal to Binary
• Converting Decimal Number to Binary format
• Write a program to convert decimal to binary
• Write a program to convert decimal number to binary format
• Write a program to convert positive decimal number to binary format
• Write a program to convert decimal to binary using Scanner class
• Write a program to convert decimal to binary, take input using Scanner class

Java Program to convert Decimal to Binary :

[sourcecode lang=”java”]
public class DecimalToBinary {

public void toBinary(int number){
int binary[] = new int[25];
int n = 0;
// Convert Decimal to Binary
while(number > 0){
binary[n++] = number%2;
number = number/2;
}
// Print Binary number
for(int i = n-1;i >= 0;i–){
System.out.print(binary[i]);
}
}

public static void main(String[] args){
DecimalToBinary obj = new DecimalToBinary();
obj.toBinary(14);
}
}
[/sourcecode]

Output :

1110

Java Program to convert Decimal to Binary using Scanner class :

[sourcecode lang=”java”]

import java.util.Scanner;

public class DecimalToBinary {

public void toBinary(int number){
int binary[] = new int[14];
int n = 0;

// Convert Decimal to Binary
while(number > 0){
binary[n++] = number%2;
number = number/2;
}

// Print Binary Number
for(int i = n-1;i >= 0;i–){
System.out.print(binary[i]);
}
}

public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter a number: ");
int num= scanner.nextInt();
DecimalToBinary obj = new DecimalToBinary();
obj.toBinary(num);

}
}

[/sourcecode]

Output :

Enter a number: 14

1110

## Java Program to find prime number upto N number

Objectives :

• Write a Java program to find prime number upto N number
• Write a Java program to print prime number upto N number
• Write a Java program to find prime number upto N number using Command Line Arguments
• Write a Java Program to find prime number upto N number via Command Line Arguments
• Write a Java program to find prime number upto N number using Scanner class

Java Program / Code :

Method 1 : Java Program to find Prime Number upto N number using Scanner class

[sourcecode lang=”Java”]

import java.util.Scanner;
{
public static void main(String[] args)
{
int n,p;
Scanner s=new Scanner(System.in);
System.out.println(“Enter number : ”);
n=s.nextInt();
for(int i=2;i<n;i++)
{
p=0;
for(int j=2;j<i;j++)
{
if(i%j==0)
p=1;
}
if(p==0){
System.out.println(i);
}
}
}
}
[/sourcecode]

Method 2 : Java Program to find Prime Number upto N number using Scanner class and writing function to find prime number

Method isPrime() for checking if a number is prime or not

[sourcecode lang=”java”]
public boolean isPrime(int num) {
if ( num < 2 ){
return false;
}
for (int i = 2; i <= Math.sqrt(num); i++) {
if ( num % i == 0 ) {
return false;
}
}
return true;
}
}

// Mock Test Class to test above code
import java.util.Scanner;

public class Demo
{
public static void main(String[] args)
{
Scanner scanner = new Scanner(System.in);

int num = scanner.nextInt();

if ( num < 2 ) {
System.out.println("\n There are no Prime Numbers available");
System.exit(0);
}
System.out.println("\n Prime Numbers from 1 to "+ num);

for (int i = 3; i <= num; i++) {
System.out.print(", " + i);
}
}
}
}
[/sourcecode]

Method 3 : Java Program to find Prime Number upto N number using Command line input

[sourcecode lang=”Java”]

{
public static void main(String[] args)
{
int n,p;
n=Integer.parseint(args[0]);
for(int i=2;i&lt;n;i++)
{
p=0;
for(int j=2;j&lt;i;j++)
{
if(i%j==0)
p=1;
}
if(p==0){
System.out.println(i);
}
}
}
}
[/sourcecode]

Steps to run above program via command line :

2. Interpretation : C:\JavaPrograms>java PrimeNumber 20

Output :

2

3

5

7

11

13

17

19

## Program to find Sum of Digits in Java

Objectives :

• Write a program to compute sum of digits of a given number.
• Write a program to find sum of digits of a given number.
• Write a program to calculate sum of digits of a given number.
• Write a program to compute sum of digits of a given integer number.
• Write a program to compute sum of digits of a number entered via Command Line.
• Write a program to compute sum of digits of a given number. Take input from Command Line.
• Write a program to compute sum of digits of a given number. Take input using Scanner class.

Following is the Java Program to compute Sum of Digits of a given integer number;

Method 1 : Java Program to find Sum of Digits when number is entered from command line

[sourcecode lang=”java”]

class SumOfDigits
{
public static void main(String args[])
{
int n;
int a=0;
int sum=0;

//taking integer number from command line and parsing the same
n=Integer.parseInt(args[0]);

while(n!=0)
{
a=n%10;
n=n/10;
sum=sum+a;
}
System.out.println("Sum of digits: " + sum);
}
}

[/sourcecode]

Steps to run above program via command line :

1. Compilation : C:\JavaPrograms>javac SumOfDigits.java
2. Interpretation : C:\JavaPrograms>java SumOfDigits 12345

Output : Sum of digits: 15

Method 2 : Java Program to find Sum of Digits if input is taken using Scanner class

[sourcecode lang=”java”]

import java.util.Scanner;

public class SumOfDigits {
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
int n;
int a=0;
System.out.print("Enter a positive number: ");
n = in.nextInt();

if (n <= 0)
System.out.println("You have entered a negative number.");
else {
int sum = 0;

while (n != 0) {

a=n%10;
n=n/10;
sum=sum+a;
}
System.out.println("Sum of digits: " + sum);
}
}
}

[/sourcecode]

Steps to run above program via command line :

1. Compilation : C:\JavaPrograms>javac SumOfDigits.java
2. Interpretation : C:\JavaPrograms>java SumOfDigits 12345

Output :

Trial 1 : With positive number

Enter a positive number: 12345

Sum of digits: 15

Trial 2 : With negative number

Enter a positive number: -12345

You have entered a negative number.

## Simple Interest Example in Java

Starting a series of some Java programs as many students were asking to share the programs. Here is the first program of the series.

Objectives:

• Write a Program that calculates and prints the simple interest using the formula : Simple Interest = PTR/100
• How to calculate Simple Interest in Java?
• Write a program to calculate Simple Interest in Java.
• Write a Java program that calculates and prints the simple interest using the formula : “SimpleInterest = PTR/100” and input values P, T, R should be accepted as command line.
• How to use Command Line Arguments in Java?
• How to pass values from command line in Java?
• How to take input in Java from console?

This particular program can be written in various ways, we will try to write the solution program in different ways here and one can try to understand the difference between them.

Method 1 :

[sourcecode lang=”java”]
import java.util.Scanner;

public class SimpleInterestExample {

public static void main(String[] args) {

int p,t,r, result;

Scanner sc = new Scanner(System.in);

System.out.println(&quot;Enter the Value of P : &quot;);
p = sc.nextInt();

System.out.println(&quot;Enter the Value of T : &quot;);
t = sc.nextInt();

System.out.println(&quot;Enter the Value of R : &quot;);
r = sc.nextInt();

result = (p*t*r)/100;
System.out.println(&quot;Interest is : &quot; + result);
}
}
[/sourcecode]

This one is the simplest way to write the program to find simple interest in Java. Here we have simply created the object of Scanner class for taking input. Scanner class was introduced in Java 6. To use Scanner class we will have to import the class from java.util package.

Method 2:

Now we will write a Java program that calculates and prints the simple interest using the Scanner class again but with object oriented programming approach.

[sourcecode lang=”java”]
import java.util.Scanner;

public class SimpleInterestExample
{
double principalAmount = 0;
double interestRate = 0;
double term = 0;
double simpleInterest = 0;

public void calculateSimpleInterest()
{
Scanner input = new Scanner(System.in);

System.out.print(&quot;Enter the Principal amount : &quot;);
principalAmount = input.nextDouble();

System.out.print(&quot;Enter the Rate As a decimal : &quot;);
interestRate = input.nextDouble();

System.out.print(&quot;Enter the amount of time in years : &quot;);
term = input.nextDouble();

simpleInterest = (principalAmount * interestRate * term) / 100;
}

public void displaySimpleInterest()
{
System.out.println(&quot;The Simple Interest is : &quot; + simpleInterest);
}
}
[/sourcecode]

Mock Test Program for above code so that we can test the code. keep both the classes in same package and run the Mock Test Program or MockTestProgram.java

[sourcecode lang=”java”]
public class MockTestProgram{

public static void main(String[]args);
{
SimpleInterestExample simpleInt = new SimpleInterestExample();
simpleInt.calculateSimpleInterest();
simpleInt.displaySimpleInterest();
}
}
[/sourcecode]

Method 3:

Now we will write a Java program that calculates and prints the simple interest using the formula : “SimpleInterest = PTR/100” and input values P, T, R should be accepted as command line.

[sourcecode lang=”java”]
import java.util.Scanner;

public class SimpleInterestExample {

public static void main(String[] args) {
double p,t,r, result;

p = Double.parseDouble(args[0]);
t = Double.parseDouble(args[1]);
r = Double.parseDouble(args[2]);

Scanner sc = new Scanner(System.in);

System.out.println(&quot;Enter the Value of P : &quot;);
p = sc.nextDouble();

System.out.println(&quot;Enter the Value of T : &quot;);
t = sc.nextDouble();

System.out.println(&quot;Enter the Value of R : &quot;);
r = sc.nextDouble();

result = (p*t*r)/100;
System.out.println(&quot;Interest is : &quot; + result);
}
}
[/sourcecode]

I will be sharing more programs soon as many students were asking for programs which were carried out during Java training and were asked in assignments after Java training. By the time enjoy coding in Java and use NetBeans, it will ease your life.

## 7 differences between HashMap and HashTable

Objectives:

• What is HashMap?
• What is HashMap in Java?
• What is HashTable?
• What is HashTable in Java?
• What are the differences between HashMap and HashTable?
• What are the differences between HashMap and HashTable in Java?

HashMap vs HashTable

1. HashMap is non-synchronized. HashTable is synchronized.

3. HashMap allows one null key and any number of null values while HashTable do not allow null keys and null values in HashTable Object.

4. HashMap object values are iterated using iterator. HashTable is only class other than Vector class which uses enumerator to iterate values of HashTable object.

5. The iterator in HashMap is fail-fast iterator while enumerator for HashTable is not.

6. HashMap is much faster and uses less memory than HashTable.

7. HashMap is subclass of AbstractMap class. HashTable is subclass of Dictionary class which is obsolete in 1.7 and not in use anymore.

## Book : NetBeans IDE How-to Instant

NetBeans IDE How-to : Atul Palandurkar : Packt Publishing, UK

I was asked to write a book for Java Application Development using NetBeans IDE by PACKT Publishing, UK which is one of the leading technology books publishers in world. It will be a great experience to work with the great publishing house and their team. Thanks a lot Packt & Team.

I know, Java and NetBeans community will definitely accept the book with a grand welcome. The book is intended for Java Developers who are not aware of NetBeans IDE or those who have experience of Java development but have not used NetBeans for development of Java applications. This book can be referred by novice also to learn Java and Java application development using NetBeans IDE very easily.

My outline (contents) was selected out of few other authors and then after we signed the contract, now the book is complete and very soon the book will hit the market in different formats by the publisher in March 2013.

I just love it, I have tried my best in writing this book and to make it easier for novice to experts. It was a great pleasure working with Packt Team.

You will learn many things from this book such as :

• Use NetBeans IDE for Java technologies
• Develop a HelloWorld application with NetBeans IDE
• Explore the layout of NetBeans IDE
• Develop different Java applications in NetBeans
• Use the Visual Designer
• Design Java projects
• Develop web applications using NetBeans IDE