Java

Singleton Design pattern in JAVA

Mallik4 Comments

Below class depicts the Singleton design pattern.

SingletonDesignPattern.java

package in.javatutorials;

/**
* @author JavaTutorials
* @version 1.0
*
*/
public final class SingletonDesignPattern {

/**
* make the class object as private as it is
* not used directly out side the class
*/
private static SingletonDesignPattern singletonObj = null;

/**
* make the constructor as private.
* Object cannot be created using the constructor outside of this class.
*/
private SingletonDesignPattern(){

}

/**
* Create the class object if it is null and
*
* @return singletonObj SingletonDesignPattern
*/
public static SingletonDesignPattern getInstance(){
if(singletonObj == null){
singletonObj = new SingletonDesignPattern();
}
return singletonObj;
}

/**
* Take the user name as parameter and return the welcome message
*
* @param userName String
* @return message String
*/
public String getWelcomeInfo(String userName){
String message = null;
//make method access to synchronized to make thread safe
synchronized (SingletonDesignPattern.class) {
System.out.println(“User Name is : ” + userName);
message = “Hello ” + userName + “!!!”;
}
return message;
}
}

 

TestSingleton.java

The main() method of below class will get the single ton object and access the other methods using the same.

package in.javatutorials;

public class TestSingleton {

public static void main(String[] args) {
//Get the singleton object
SingletonDesignPattern singletonObj = SingletonDesignPattern.getInstance();

System.out.println(singletonObj.getWelcomeInfo(“Mallik”));
}

}

Convert Array to Vector in Java

Mallik4 Comments

package com.test;

import java.util.Arrays;
import java.util.Vector;

public class ArrayTest {

public static void main(String[] args) {
ArrayTest arrayTest = new ArrayTest();
arrayTest.arrayToVector();
}
public void arrayToVector() {

String[] arrayToConvert = { “jhony”, “peter”, “don” };

Vector<String> convertedVector = new Vector<String> Arrays.asList(arrayToConvert));

System.out.println(“11111 ” + convertedVector.get(0));

System.out.println(“3” + convertedVector.size());
}
}

What are the benefits of XML?

MallikLeave a comment

There are many benefits of using XML on the Web:

  • Simplicity– Information coded in XML is easy to read and understand, plus it can be processed easily by computers.
  • Openness– XML is a W3C standard, endorsed by software industry market leaders.
  • Extensibility – There is no fixed set of tags. New tags can be created as they are needed.
  • Self-description– In traditional databases, data records require schemas set up by the database administrator. XML documents can be stored without such definitions, because they contain meta data in the form of tags and attributes.
  • Contains machine-readable context information- Tags, attributes and element structure provide context information that can be used to interpret the meaning of content, opening up new possibilities for highly efficient search engines, intelligent data mining, agents, etc.
  • Separates content from presentation– XML tags describe meaning not presentation. The motto of HTML is: “I know how it looks”, whereas the motto of XML is: “I know what it means, and you tell me how it should look.” The look and feel of an XML document can be controlled by XSL style sheets, allowing the look of a document to be changed without touching the content of the document. Multiple views or presentations of the same content are easily rendered.
  • Supports multilingual documents and Unicode-This is important for the internationalization of applications.
  • Facilitates the comparison and aggregation of data – The tree structure of XML documents allows documents to be compared and aggregated efficiently element by element.
  • Can embed multiple data types – XML documents can contain any possible data type – from multimedia data (image, sound and video) to active components (Java applets, ActiveX).
  • Can embed existing data – Mapping existing data structures like file systems or relational databases to XML is simple. XML supports multiple data formats and can cover all existing data structures.
  • Provides a ‘one-server view’ for distributed data – XML documents can consist of nested elements that are distributed over multiple remote servers. XML is currently the most sophisticated format for distributed data – the World Wide Web can be seen as one huge XML database.

Java EE 5 vs Java EE 6

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This post visualizes changes between Java EE Standards 5 and 6. The comparison of standards is listed in four sections Web-Services, Web-Container, Enterprise Application technologies and Maintenance. Hope this helps someone.

Web Service related changes

JAVA EE 5 (JSR-244) JAVA EE 6 (JSR-316)
JAX-RPC 1.1 JSR 101 JAX-RPC 1.1
Enterprise Web Services 1.2 JSR 109 Enterprise Web Services 1.3 (new version)
Web Service Metadata 1.0 JSR 181 Web Service Metadata 1.0
Streaming API for XML 1.0 JSR 173 Streaming API for XML 1.0
JAX-WS 2.0  JSR 224 JAX-WS 2.2 (new version)
JAXB 2.0 JSR 222 JAXB 2.2 (new version)
SOAP with Attachments API for Java (SAAJ)JSR 67 Java APIs for XML Messaging 1.3 (new version)spec
new! JAX-RS 1.1 JSR 311
new! Java API for XML Registries (JAXR 1.0)JSR 93

The new redesigned Java API for XML Web Services (JAX-WS) is the base or a middle part of a newly Java EE 6 Web service stack.  The new stack  includes JAX-WS 2.0, JAXB 2.0, and SAAJ 1.3. and is also called “integrated stack”.  JAX-WS was designed to take place of JAX-RPC. Due this also JSR-109 was updated because it describes run time architecture of JEE Web Services Stack. JAXB which provides an easy way to bind an XML schema to java and vice verse, was updated to.

The SOAP with Attachments API for Java (SAAJ) (also known as Java APIs for XML Messaging (JAXM)) provides a standard way to send XML documents over the Internet from the Java platform and was updated slightly containing now other consolidated standard.

New are JAX-RS, which provides support for RESTful Web services and JAXR which enables pull-parsing API for reading and writing XML documents. Also available in Java SE.

Web Applications related changes

JAVA EE 5 JAVA EE 6
JSTL JSR 52 JSTL
JavaServer Faces 1.2 JSR 252 JavaServer Faces 2.0 (new version)
JavaServer Pages 2.1 JSR 245 JavaServer Pages 2.2 /EL 2.2 (new version)
Java Servlet 2.5 JSR 154 Java Servlet 3.0 JSR 315 (new version)
new! Debugging Support for Other Languages 1.0 JSR 45

In Java EE 6 we have updates of all technologies of the Web Container except JSTL. So e.g. Servlet 3.0 improves Servlet concept in pluggability and some ease of development. It’s also introduces Async Servlet, and long waited File Uploading!. Also now configuration can be done by annotations.

New a specification of Debugging Support for Other Languages 1.0
This describes standardized tools for correlating Java virtual machine byte code to source code of languages other than the Java programming language, so it would guarantee debugging possibility of everything what runs is JSR-45 certified container.

Enterprise Technologies changes

JAVA EE 5 JAVA EE 6
Common Annotations JSR 250 Common Annotations
JCA 1.5 JSR 112 JCA 1.6 JSR 322 (new version)
JavaMail 1.4 JavaMail 1.4
JMS 1.1 JSR 914 JMS 1.1
JTA 1.1 JSR 907 JTA 1.1
Enterprise JavaBeans 3.0 JSR 220 Enterprise JavaBeans 3.1 JSR 318
(new version)
JPA 1.0 JSR 220 (together with EJB 3.0) JPA 2.0 JSR 317 (new version)
new! Contexts and Dependency Injection for Java (Web Beans 1.0) JSR 299
new! Dependency Injection for Java 1.0 JSR 330
new! Bean Validation 1.0 JSR 303
new! Managed Beans 1.0 JSR-316

In Enterprise Application section we see some important changes and new specifications. Most famous and important is  JSR-299 Context and Dependency Injection (CDI) which is there to unify the JavaServer Faces-managed bean component model with the Enterprise JavaBeans component model to simplify the programming model and architecture of web-based applications. Look an Weld Framework as reference implementation to this.

The similar sounding Standard Dependency Injection for Java JSR-330 just define a standard and common known DI like in spring and other frameworks. Look at popular Guice DI-Framework from Google which implements JSR-330.

Bean Validation  introduces a very cool annotation based and architecture layer independent Java Bean validation.

There are also some interesting improvements in EJBs. Singleton is a new type and can be only one per container, it is also possible to use @Local Beans (Same VM) without interface. Also JPA 2.0 has advanced query possibilities and validation.

Management Technologies

JAVA EE 5 JAVA EE 6
J2EE Application Deployment 1.2 JSR 88 J2EE Application Deployment 1.2
JavaBeans Activation Framework (JAF) 1.1 JSR 925 JavaBeans Activation Framework (JAF) 1.1
J2EE Management 1.0  JSR 77 J2EE Management 1.1 (new version)
Java Authorization Contract for Containers 1.1 JSR 115 Java Authorization Contract for Containers 1.3(new version)
new! Java Authentication Service Provider Interface for Containers JSR 196
new! [JavaSE] JAXP 1.3 JSR 206
new! [JavaSE] JDBC 4.0 JSR 221
new! [JavaSE] JMX 2.0 JSR 255

Nothing special to mention here.

How to Copy an Array into Another Array?

Mallik1 Comment

Contents of one array can be copied into another array by using the arraycopy() method of the System class in Java.

  • arraycopy() method accepts source array, source length, destination array and destination length.
  • Following program shows the use of arraycopy() method to copy the contents of one array to another.
package com.Test;

public class ArrayCopyTest{
 public static void main(String[] args){
    int[] src = new int[] {1, 2, 3, 4, 5};
    int[] dest = new int[src.length];
    System.arraycopy(src, 0, dest, 0, src.length);
    for (int i = 0; i < dest.length; i++){
       System.out.println(dest[i]);
    }
  }
}

How to check duplicated value in array

MallikLeave a comment 

package com.test;

import java.util.Set;
import java.util.HashSet;

public class CheckDuplicate
{
	public static void main(String args[])
	{
		String [] sValue = new String[]{"a","b","c","d","","","e","a"};

		if(checkDuplicated_withNormal(sValue))
			System.out.println("Check Normal : Value duplicated! \n");
		if(checkDuplicated_withSet(sValue))
			System.out.println("Check Set : Value duplicated! \n");

	}

	//check duplicated value
	private static boolean checkDuplicated_withNormal(String[] sValueTemp)
	{
		for (int i = 0; i < sValueTemp.length; i++) {
			String sValueToCheck = sValueTemp[i];
			if(sValueToCheck==null || sValueToCheck.equals(""))continue; //empty ignore
			for (int j = 0; j < sValueTemp.length; j++) {
					if(i==j)continue; //same line ignore
					String sValueToCompare = sValueTemp[j];
					if (sValueToCheck.equals(sValueToCompare)){
							return true;
					}
			}

		}
		return false;

	}

	//check duplicated value
	private static boolean checkDuplicated_withSet(String[] sValueTemp)
	{
		Set<String> sValueSet = new HashSet<String>();
		for(String tempValueSet : sValueTemp)
		{
			if (sValueSet.contains(tempValueSet))
				return true;
			else
				if(!tempValueSet.equals(""))
					sValueSet.add(tempValueSet);
		}
		return fals

How to create XML file in Java

Mallik1 Comment

package com.test;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class CreateXMLInJava {

public static void main(String argv[]) {
CreateXMLInJava createXml = new CreateXMLInJava();
createXml.createXML();
}

public void createXML() {
try {
DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();

// root elements
Document doc = docBuilder.newDocument();
Element rootElement = doc.createElement(“Company”);
doc.appendChild(rootElement);

// staff elements
Element staff = doc.createElement(“Dept”);
rootElement.appendChild(staff);

// set attribute to staff element
Attr attr = doc.createAttribute(“id”);
attr.setValue(“1”);
staff.setAttributeNode(attr);

// can be written as
// staff.setAttribute(“id”, “1”);

// firstname elements
Element firstname = doc.createElement(“Firstname”);
firstname.appendChild(doc.createTextNode(“mallik”));
staff.appendChild(firstname);

// lastname elements
Element lastname = doc.createElement(“Lastname”);
lastname.appendChild(doc.createTextNode(“Gunda”));
staff.appendChild(lastname);

// salary elements
Element salary = doc.createElement(“Salary”);
salary.appendChild(doc.createTextNode(“100000”));
staff.appendChild(salary);

// write the content into xml file
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
StreamResult result = new StreamResult(new File(“D:\\test.xml”));

// Output to console for testing
// StreamResult result = new StreamResult(System.out);

transformer.transform(source, result);

System.out.println(“File saved!”);

} catch (ParserConfigurationException pce) {
pce.printStackTrace();
} catch (TransformerException tfe) {
tfe.printStackTrace();
}
}
}

Read Excel file in Java using POI API

Mallik2 Comments

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Iterator;
public class ReadExcelFileUsingPOI{
    public static void main(String[] args) throws Exception {
        String filename = "D:\\test.xls";
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(filename);
            HSSFWorkbook workbook = new HSSFWorkbook(fis);
            HSSFSheet sheet = workbook.getSheetAt(0);
            Iterator rows = sheet.rowIterator();
            while (rows.hasNext()) {
                HSSFRow row = (HSSFRow) rows.next();
                Iterator cells = row.cellIterator();
                while (cells.hasNext()) {
                    HSSFCell cell = (HSSFCell) cells.next();
                    int type = cell.getCellType();
                    if (type == HSSFCell.CELL_TYPE_STRING) {
                        System.out.println("[" + cell.getRowIndex() + ", "
                                + cell.getColumnIndex() + "] = STRING; Value = "
                                + cell.getRichStringCellValue().toString());
                    } else if (type == HSSFCell.CELL_TYPE_NUMERIC) {
                        System.out.println("[" + cell.getRowIndex() + ", "
                                + cell.getColumnIndex() + "] = NUMERIC; Value = "
                                + cell.getNumericCellValue());
                    } else if (type == HSSFCell.CELL_TYPE_BOOLEAN) {
                        System.out.println("[" + cell.getRowIndex() + ", "
                                + cell.getColumnIndex() + "] = BOOLEAN; Value = "
                                + cell.getBooleanCellValue());
                    } else if (type == HSSFCell.CELL_TYPE_BLANK) {
                        System.out.println("[" + cell.getRowIndex() + ", "
                                + cell.getColumnIndex() + "] = BLANK CELL");
                    }
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                fis.close();
            }
        }
    }
}

Percentage Calculation in Java

MallikLeave a comment

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public final class Percent {

public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println(“enter the total no.of sub”);
int n = Integer.parseInt(br.readLine());
int marks[] = new int[n];
int i, tot = 0;
for (i = 0; i < n; i++) {
System.out.println(“enter ur marks”);
marks[i] = Integer.parseInt(br.readLine());
tot = tot + marks[i];
}
System.out.println(“total marks: ” + tot);
System.out.println(“percentage of marks: ” + (float) tot / n);
}
}

How to Create Excel file in Java using POI API

Mallik1 Comment


import java.io.FileOutputStream;


import org.apache.poi.hssf.usermodel.HSSFRow;

import org.apache.poi.hssf.usermodel.HSSFSheet;

import org.apache.poi.hssf.usermodel.HSSFWorkbook;


public class CreateExcelFile {

public static final String FILE_NAME = “D:\\test.xls”;


 public void createExcelFile(String filename) {

try {

HSSFWorkbook hwb = new HSSFWorkbook();

HSSFSheet sheet = hwb.createSheet(“Sheet1”);

 

HSSFRow rowhead = sheet.createRow((short) 0);

rowhead.createCell((short) 0).setCellValue(“S.No.”);

rowhead.createCell((short) 1).setCellValue(“Emp ID”);

rowhead.createCell((short) 2).setCellValue(“EMP Name”);

rowhead.createCell((short) 3).setCellValue(“Dept”);

 

rowhead = sheet.createRow((short) 1);

rowhead.createCell((short) 0).setCellValue(“1”);

rowhead.createCell((short) 1).setCellValue(“EMP1”);

rowhead.createCell((short) 2).setCellValue(“Mallik”);

rowhead.createCell((short) 3).setCellValue(“Java”);


FileOutputStream fileOut = new FileOutputStream(filename);

hwb.write(fileOut);

fileOut.close();

System.out.println(“Your excel file has been generated!”);


 } catch (Exception ex) {

System.out.println(ex);

ex.printStackTrace();

}

}

public static void main(String[] args) {

CreateExcelFile excelFile = new CreateExcelFile();

excelFile.createExcelFile(FILE_NAME);

}

}