java programs - Connect2java

Print occurrence of integer in java

Solution: There will be many ways to solve this problem, but here we are giving two solutions to print occurrence of integer 1) Printing occurrence of integer using Collections.freequence() method 2) Printing occurrence of integer using HashMap



import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;

public class OccurrenceOfIntger {

	public static void main(String[] args) {
		
		List<Integer> c = new ArrayList<Integer>();
		
		c.add(1);
		c.add(1);
		c.add(3);
		c.add(4);
		c.add(5);
		c.add(5);
		c.add(5);
		c.add(5);
		
		//print occurrence using Collections.freequency() method
		printOccurrence(c);
		
		//print occurrence using HashMap
		printOccurrenceUsingHashMap(c);
		
	}
	
	private static void printOccurrence(List<Integer> c) {
		
		for(Integer number : c){
			
			System.out.println(number +" : " + Collections.frequency(c, number) );			
		}		
	}
	
	private static void printOccurrenceUsingHashMap(List<Integer> c) {
		
		HashMap<Integer,Integer> map =new HashMap<Integer,Integer>();
		
		for(Integer number:c){

			if(map.get(number)==null)
				map.put(number, 1);
			else 
				map.put(number,   map.get(number) + 1 );
		}
		
		System.out.println(map);
		
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.List;

public class OccurrenceOfIntger {

public static void main(String[] args) {

List<Integer> c = new ArrayList<Integer>();

c.add(1);

c.add(3);

c.add(4);

c.add(5);

//print occurrence using Collections.freequency() method

printOccurrence(c);

//print occurrence using HashMap

printOccurrenceUsingHashMap(c);

}

private static void printOccurrence(List<Integer> c) {

for(Integer number : c){

System.out.println(number +" : " + Collections.frequency(c, number) );

}

private static void printOccurrenceUsingHashMap(List<Integer> c) {

HashMap<Integer,Integer> map =new HashMap<Integer,Integer>();

for(Integer number:c){

if(map.get(number)==null)

map.put(number, 1);

else

map.put(number, map.get(number) + 1 );

}

System.out.println(map);

}

Output



1 : 2
1 : 2
3 : 1
4 : 1
5 : 4
5 : 4
5 : 4
5 : 4
{1=2, 3=1, 4=1, 5=4}

1

2

3

4

5

6

7

8

9

10

11

12

13

1 : 2

3 : 1

4 : 1

5 : 4

{1=2, 3=1, 4=1, 5=4}

Reverse a string in java with or without using StringBuilder api

Solution: In this program there are 3 solutions 1) Reverse string using StringBuilder API 2) Reverse string by reading from end of the string 3) Reverse string by using Recursion



public class ReverseString {
	
	public static void main(String[] args) {
		
		
		// Reversing string using StringBuilder
		reverseUsingStringBuilder(new StringBuilder("htaneers"));
		
		//Reversing string by reading from end
		revereString("htaneers");
		
		//Reversing string using recursive
		System.out.println(reverseStringRecursively("htaneers"));
		
		
	}
	
	
	private static void reverseUsingStringBuilder(StringBuilder sb) {
		
		System.out.println(sb.reverse());
		
	}
	
	private static void revereString(String string) {
		
		char[] ch = string.toCharArray();
		
		for(int i=ch.length-1; i>=0;i--)
			System.out.print(ch[i]);
		
		System.out.println();
		
	}

	private static String reverseStringRecursively(String string) {
		
		if(string.length()==1) 
				return string;
		
		return reverseStringRecursively(string.substring(1)) + string.charAt(0);
		
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

public class ReverseString {

public static void main(String[] args) {

// Reversing string using StringBuilder

reverseUsingStringBuilder(new StringBuilder("htaneers"));

//Reversing string by reading from end

revereString("htaneers");

//Reversing string using recursive

System.out.println(reverseStringRecursively("htaneers"));

}

private static void reverseUsingStringBuilder(StringBuilder sb) {

System.out.println(sb.reverse());

}

private static void revereString(String string) {

char[] ch = string.toCharArray();

for(int i=ch.length-1; i>=0;i--)

System.out.print(ch[i]);

System.out.println();

}

private static String reverseStringRecursively(String string) {

if(string.length()==1)

return string;

return reverseStringRecursively(string.substring(1)) + string.charAt(0);

}

Output



sreenath
sreenath
sreenath

1

2

3

4

5

6

7

sreenath

Write a program to generate a random integer in a specified range

Solution



public class GenerateRandomIntegerInRange {

	public static void main(String[] args) {
		
		for(int i=0;i<10;i++)
		System.out.println(generateRandomIntegerInRange(11,20));
		
	}
	
	/*
	 *  Returns the random integer in specified range 
	 */
	
	public static int generateRandomIntegerInRange(int min, int max){
        return min + (int)(Math.random()*((max - min) + 1));		
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

public class GenerateRandomIntegerInRange {

public static void main(String[] args) {

for(int i=0;i<10;i++)

System.out.println(generateRandomIntegerInRange(11,20));

}

/*

* Returns the random integer in specified range

*/

public static int generateRandomIntegerInRange(int min, int max){

return min + (int)(Math.random()*((max - min) + 1));

}

Output

1

2

3

4

5

6

7

8

9

10

11

12

13

14

20

14

13

15

13

18

19

11

Find the Missing Number in array

You are given a list of n-1 numbers and these numbers are in the range of 1 to n. There are no duplicates in list. One of the number is missing in the list. Write a program to find the missing number. Example:



I/P    [1, 2, 4, 5, 6, 3, 7, 8, 10]

O/P    9

1

2

3

4

5

6

7

I/P [1, 2, 4, 5, 6, 3, 7, 8, 10]

O/P 9

Solution:



1. Calculate the sum of the series using below formula.
       total = n*(n+1)/2

2. Calculate sum of the numbers in an given array

3. (total - sum) will be missing number in array

1

2

3

4

5

6

7

8

9

10

1. Calculate the sum of the series using below formula.

total = n*(n+1)/2

2. Calculate sum of the numbers in an given array

3. (total - sum) will be missing number in array



import java.util.Arrays;


public class FindMissingNumber {

	public static void main(String[] args) {
		
		// Only one missing number in array
        int[] arr = new int[]{1, 2, 4, 5, 6, 3, 7, 8, 10};
        
        int missing = getMissingNumber(arr, 10);
        
        System.out.printf("Missing number in array %s is %d %n", 
        		Arrays.toString(arr), missing);
	}
	
	
	 private static int getMissingNumber(int[] numbers, int n) {
	    
		 	int total = n * (n + 1) / 2;
	        int sum = 0;
	        for (int i : numbers) {
	        	sum += i;
	        }
	 
	        return total - sum;
	    }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

import java.util.Arrays;

public class FindMissingNumber {

public static void main(String[] args) {

// Only one missing number in array

int[] arr = new int[]{1, 2, 4, 5, 6, 3, 7, 8, 10};

int missing = getMissingNumber(arr, 10);

System.out.printf("Missing number in array %s is %d %n",

Arrays.toString(arr), missing);

}

private static int getMissingNumber(int[] numbers, int n) {

int total = n * (n + 1) / 2;

int sum = 0;

for (int i : numbers) {

sum += i;

}

return total - sum;

}

Output



Missing number in array [1, 2, 4, 5, 6, 3, 7, 8, 10] is 9

1

2

3

4

5

Missing number in array [1, 2, 4, 5, 6, 3, 7, 8, 10] is 9

How to find maximum and minimum value from an array



public class FindMaxMinArray {

	public static void main(String[] args) {
		
		int[] a ={10,20,5,-1,6,77,30,45,78,110000000,25,-25};
		
		printMaxMin(a);
		
	}

	private static void printMaxMin(int[] a) {
		
		int max=a[0];
		int min=a[0];
		
		for(int i=0;i<a.length;i++){
			
			if(a[i] > max)
				max=a[i];
			
			if(a[i] < min)
				min=a[i];
			
		}
		
		System.out.println("max :"+ max);
		System.out.println("min :"+ min);
		
	}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

public class FindMaxMinArray {

public static void main(String[] args) {

int[] a ={10,20,5,-1,6,77,30,45,78,110000000,25,-25};

printMaxMin(a);

}

private static void printMaxMin(int[] a) {

int max=a[0];

int min=a[0];

for(int i=0;i<a.length;i++){

if(a[i] > max)

max=a[i];

if(a[i] < min)

min=a[i];

}

System.out.println("max :"+ max);

System.out.println("min :"+ min);

}

Output



max :110000000
min :-25

1

2

3

4

5

6

max :110000000

min :-25

How to generate Random passwords using java.util.Random API?

in this example we will see sample program to generate Random passwords using java.util.Random API



import java.util.Random;

public class GenerateRandomPassword {

public static void main(String[] args) {
	
	// Prints 10 random passwords
	for(int i=1;i<=10;i++)
		System.out.println(generateRandomPassword());
}

private static String generateRandomPassword() {

	 Random radmon = new Random();	
	 String passwordCharacters = "abcdefghijklmnopqrstuvwxyz" +
	 		"ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
	    
	    char[] password = new char[8];
	    for (int i = 0; i < 8; i++)
	    {
	    	password[i] = passwordCharacters.charAt
	    			(radmon.nextInt(passwordCharacters.length()));
	    }
	    return new String(password);
}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

import java.util.Random;

public class GenerateRandomPassword {

public static void main(String[] args) {

// Prints 10 random passwords

for(int i=1;i<=10;i++)

System.out.println(generateRandomPassword());

}

private static String generateRandomPassword() {

Random radmon = new Random();

String passwordCharacters = "abcdefghijklmnopqrstuvwxyz" +

"ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";

char[] password = new char[8];

for (int i = 0; i < 8; i++)

{

password[i] = passwordCharacters.charAt

(radmon.nextInt(passwordCharacters.length()));

}

return new String(password);

}

Output



z4QTq2ml
pAgyYUhx
AxA558OC
SEX1yLfs
cITZGLIP
AE2Cukrw
ia12n1sg
N9RhRDNw
8aNvuSLD
unsgUSro

1

2

3

4

5

6

7

8

9

10

11

12

13

14

z4QTq2ml

pAgyYUhx

AxA558OC

SEX1yLfs

cITZGLIP

AE2Cukrw

ia12n1sg

N9RhRDNw

8aNvuSLD

unsgUSro

How to pretty print XML from Java?

I have an xml which is non-format as below. How i can make it nicely formatted xml.



<?xml version="1.0"?>
<catalog><book id="bk101"><author>Amuthan G</author><title>Spring MVC: Beginner's Guide</title><genre>Computer</genre> <price>40.49</price><publish_date>2014-07-25</publish_date><description>Your ultimate guide to building a complete web application using all the capabilities of Spring MVC</description></book><book id="bk102"><author> J. Sharma, Ashish Sarin</author><title>Getting started with Spring Framework</title><genre>Computer</genre><price>14.01</price>
<publish_date>2012-12-10</publish_date><description>Getting started with Spring Framework is a hands-on guide to begin developing applications using Spring Framework.</description></book><book id="bk103"><author>Herbert Schildt</author><title>Java, A Beginner's Guide</title><genre>Computer</genre><price>37.75</price><publish_date>2011-08-16</publish_date><description>Learn the fundamentals of Java programming in no time from bestselling programming author Herb Schildt.</description></book></catalog>

1

2

3

4

5

6

7

<?xml version="1.0"?>

<catalog><book id="bk101"><author>Amuthan G</author><title>Spring MVC: Beginner's Guide</title><genre>Computer</genre> <price>40.49</price><publish_date>2014-07-25</publish_date><description>Your ultimate guide to building a complete web application using all the capabilities of Spring MVC</description></book><book id="bk102"><author> J. Sharma, Ashish Sarin</author><title>Getting started with Spring Framework</title><genre>Computer</genre><price>14.01</price>

<publish_date>2012-12-10</publish_date><description>Getting started with Spring Framework is a hands-on guide to begin developing applications using Spring Framework.</description></book><book id="bk103"><author>Herbert Schildt</author><title>Java, A Beginner's Guide</title><genre>Computer</genre><price>37.75</price><publish_date>2011-08-16</publish_date><description>Learn the fundamentals of Java programming in no time from bestselling programming author Herb Schildt.</description></book></catalog>

Pass the books.xml in the below program , run the program and see output.



import org.w3c.dom.Document;
import org.xml.sax.SAXException;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream; 
import java.io.FileNotFoundException;
import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;


public class XMLPrettyPrint {
	
public static void main(String[] args) throws ParserConfigurationException,
FileNotFoundException, SAXException, IOException {
	
	
	 DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();  
	 DocumentBuilder builder;  
	     
	 builder = factory.newDocumentBuilder();
	 Document doc = builder.parse(new FileInputStream
			 (new File("C://Users/Sreenath/Desktop/books.xml")));	      
	    
	 String str = xmlPrettyPrint(doc,"UTF-8");
	 
	 System.out.println(str);
	
}


public static String xmlPrettyPrint(Document doc, String encoding) {
    
	String xmlString = null;
	try {
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        ByteArrayOutputStream xmlBytes = new ByteArrayOutputStream();
        Transformer transformer = transformerFactory.newTransformer();
        if(encoding != null) {
        	transformer.setOutputProperty(OutputKeys.ENCODING, encoding);
        	transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
        } else {
        	transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");            	
        }
        transformer.setOutputProperty(OutputKeys.METHOD, "xml");
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
        transformer.transform(new DOMSource(doc), new StreamResult(xmlBytes));
        xmlString = xmlBytes.toString();
        
    } catch (Exception e) {
    	e.printStackTrace();
    }
    
    return xmlString;
}
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

import org.w3c.dom.Document;

import org.xml.sax.SAXException;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.transform.OutputKeys;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.dom.DOMSource;

import javax.xml.transform.stream.StreamResult;

public class XMLPrettyPrint {

public static void main(String[] args) throws ParserConfigurationException,

FileNotFoundException, SAXException, IOException {

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

DocumentBuilder builder;

builder = factory.newDocumentBuilder();

Document doc = builder.parse(new FileInputStream

(new File("C://Users/Sreenath/Desktop/books.xml")));

String str = xmlPrettyPrint(doc,"UTF-8");

System.out.println(str);

}

public static String xmlPrettyPrint(Document doc, String encoding) {

String xmlString = null;

try {

TransformerFactory transformerFactory = TransformerFactory.newInstance();

ByteArrayOutputStream xmlBytes = new ByteArrayOutputStream();

Transformer transformer = transformerFactory.newTransformer();

if(encoding != null) {

transformer.setOutputProperty(OutputKeys.ENCODING, encoding);

transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");

} else {

transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

}

transformer.setOutputProperty(OutputKeys.METHOD, "xml");

transformer.setOutputProperty(OutputKeys.INDENT, "yes");

transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");

transformer.transform(new DOMSource(doc), new StreamResult(xmlBytes));

xmlString = xmlBytes.toString();

} catch (Exception e) {

e.printStackTrace();

}

return xmlString;

}

Output: Now we can see that books.xml is printed in nice format.



<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<catalog>
  <book id="bk101">
    <author>Amuthan G</author>
    <title>Spring MVC: Beginner's Guide</title>
    <genre>Computer</genre> <price>40.49</price>
    <publish_date>2014-07-25</publish_date>
    <description>Your ultimate guide to building a complete web application using all the capabilities of Spring MVC</description>
  </book>
  <book id="bk102">
    <author> J. Sharma, Ashish Sarin</author>
    <title>Getting started with Spring Framework</title>
    <genre>Computer</genre>
    <price>14.01</price>
<publish_date>2012-12-10</publish_date>
    <description>Getting started with Spring Framework is a hands-on guide to begin developing applications using Spring Framework.</description>
  </book>
  <book id="bk103">
    <author>Herbert Schildt</author>
    <title>Java, A Beginner's Guide</title>
    <genre>Computer</genre>
    <price>37.75</price>
    <publish_date>2011-08-16</publish_date>
    <description>Learn the fundamentals of Java programming in no time from bestselling programming author Herb Schildt.</description>
  </book>
</catalog>

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<author>Amuthan G</author>

<title>Spring MVC: Beginner's Guide</title>

<genre>Computer</genre> <price>40.49</price>

<publish_date>2014-07-25</publish_date>

<description>Your ultimate guide to building a complete web application using all the capabilities of Spring MVC</description>

</book>

<author> J. Sharma, Ashish Sarin</author>

<title>Getting started with Spring Framework</title>

<genre>Computer</genre>

<publish_date>2012-12-10</publish_date>

<description>Getting started with Spring Framework is a hands-on guide to begin developing applications using Spring Framework.</description>

</book>

<author>Herbert Schildt</author>

<title>Java, A Beginner's Guide</title>

<genre>Computer</genre>

<publish_date>2011-08-16</publish_date>

<description>Learn the fundamentals of Java programming in no time from bestselling programming author Herb Schildt.</description>

</book>

</catalog>

How to Read/Parse CSV file in Java

In this tutorial we can learn how to parse the content from CSV file in Java. There some other APIs also there which used to parse the content from CSV file but here we are using plain Java. Have a look into the below sample program.



package simple;

import java.io.*;


public class DisplayCSVFileData {


  public static void main (String args[]) throws IOException {
    
	  File csvFile = new File("D:\\employee.csv");   
    
      System.out.println("CSV file data : " + "\n" + getCSVData(csvFile));
   
  }
  
  public static String getCSVData(File csvFile) throws IOException {

	    StringBuilder data = new StringBuilder();
	    BufferedReader br = null;
	    
	    try {
	    	br =  new BufferedReader(new FileReader(csvFile));	    
	        String line = null; 
	        while (( line = br.readLine()) != null){
	          data.append(line);
	          data.append(System.getProperty("line.separator"));
	        }   
	     }
	    catch (IOException ex){
	      ex.printStackTrace();
	    }
	    finally {
	    	  br.close();
	      }
	    
	    return data.toString();
	  }
}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

package simple;

import java.io.*;

public class DisplayCSVFileData {

public static void main (String args[]) throws IOException {

File csvFile = new File("D:\\employee.csv");

System.out.println("CSV file data : " + "\n" + getCSVData(csvFile));

}

public static String getCSVData(File csvFile) throws IOException {

StringBuilder data = new StringBuilder();

BufferedReader br = null;

try {

br = new BufferedReader(new FileReader(csvFile));

String line = null;

while (( line = br.readLine()) != null){

data.append(line);

data.append(System.getProperty("line.separator"));

}

catch (IOException ex){

ex.printStackTrace();

}

finally {

br.close();

}

return data.toString();

}

Here is the CSV file contents: […]