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02: Java 8 Streams, lambdas, intermediate vs terminal ops, and lazy loading with simple examples

A stream is an infinite sequence of consumable elements (i.e a data structure) for the consumption of an operation or iteration. Any Collection<T> can be exposed as a stream. It looks complex, but once you get it, it is very simple. The operations you perform on a stream can either...

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BeanIO Java tutorial

BeanIO is an open source Java framework for marshaling and marshaling Java beans from a flat file, stream, or simple String object. It is very powerful with support for XML, CSV, delimited and fixed length stream formats, Object binding, filed validation, integration with spring-batch, etc. Here is a basic tutorial to get started.

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Debugging like a pro with eclipse IDE tutorial for Java developers

Often you get to work on a fully functional Java application that is already in production to fix production issues or to enhance its existing functionality. As a new Java developer in the team, it is not easy to get started and contributing. The approach would be slightly different from working on a brand new project.

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Java and JAXB Tutorial – Marshaling

This blog posts extends Java and JAXB tutorial: Unmarshalling.

Q. Can you create your Java objects from XSDs?
A. Yes, you can by binding a schema. Binding a schema means generating a set of Java classes that represents the schema.

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Java and JAXB tutorial – unmarshalling

Q. What does JAXB stand for? What is an XML Binding?
A. JAXB means Java API for Xml Binding. XML binding maps an XML to in-memory Java objects. The principle advantage of using JAXB when marshaling and demarshaling XML is that is simplifies the programming model by allowing us to simply annotate a few POJOs and use the JAXB API’s and you can serialize to XML and deserialize from XML very easily.

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Java and JSON tutorial with Jackson library

Q. What is JSON and when to favor it over XML? A. JSON (JavaScript Object Notation) is a lightweight, text-based, language-netral like XML, but less verbose than XML data exchange format. JSOJ is used in Web services to exchange data between client and server. … Read more ›...

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Java and XML tutorial with DOM Parser

Q. What is a DOM parser, and when will you use it? A. The Java DOM API for XML parsing is intended for working with small to medium XML documents as an object graph in memory. The DOM parser traverses the XML file and creates the corresponding DOM objects linked together...

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Java and XML tutorial with SAX parser – reading only

Q. What is a SAX Parser and when will you use it? A. SAX (Simple API for XML) is a stream oriented API like StAX, but Unlike StAX, which can read and write, but SAX can only read. … Read more ›...

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Java and XML tutorial with StAX parser – reading

Q. What is a StAX Parser and when will you use it?
A. The StAX Java API for XML processing is designed for parsing XML streams, just like the SAX API’s, but

StAX is a “pull”

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Java and XML tutorial with Stax Parser – writing cursor based and iterator based

package com.xml;

import java.math.BigDecimal;

import org.springframework.core.style.ToStringStyler;

public class Employee {
 private String name;
 private String type;
 private int age;
 private BigDecimal salary;
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public String getType() {
  return type;
 }
 public void setType(String type) {
  this.type = type;
 }
 public int getAge() {
  return age;
 }
 public void setAge(int age) {
  this.age = age;
 }
 public BigDecimal getSalary() {
  return salary;
 }
 public void setSalary(BigDecimal salary) {
  this.salary = salary;
 }
 
 @Override
 public String toString() {
  StringBuilder sb = new StringBuilder();
  sb.append("name=" + name);
  sb.append("\n");
  if(type != null) {
   sb.append("type=" + type + "\n");
  }
  sb.append("age=" + age);
  return sb.toString();
 }
}

package com.xml;

import java.math.BigDecimal;

import org.springframework.core.style.ToStringStyler;

public class Employee {

private String name;

private String type;

private int age;

private BigDecimal salary;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getType() {

return type;

}

public void setType(String type) {

this.type = type;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public BigDecimal getSalary() {

return salary;

}

public void setSalary(BigDecimal salary) {

this.salary = salary;

}

@Override

public String toString() {

StringBuilder sb = new StringBuilder();

sb.append("name=" + name);

sb.append("\n");

if(type != null) {

sb.append("type=" + type + "\n");

}

sb.append("age=" + age);

return sb.toString();

}

Here is a simple example to write employee object to XML using simpler cursor based approach.

package com.xml;

import java.io.StringWriter;
import java.math.BigDecimal;

import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

public class StaxProcessing {

 public static void main(String[] args) {

  XMLOutputFactory factory = XMLOutputFactory.newInstance();

  // construct employee object
  Employee emp = new Employee();
  emp.setName("Peter");
  emp.setType("first");
  emp.setAge(25);
  emp.setSalary(BigDecimal.valueOf(35000.00));

  StringWriter sw = new StringWriter();

  try {
   XMLStreamWriter writer = factory.createXMLStreamWriter(sw);
   writer.writeStartDocument();
   writer.writeStartElement("Employee");
   writer.writeStartElement("name");
   writer.writeAttribute("type", "first");
   writer.writeCharacters(emp.getName());
   writer.writeEndElement();
   writer.writeStartElement("age");
   writer.writeCharacters(new Integer(emp.getAge()).toString());
   writer.writeEndElement();
   writer.writeStartElement("salary");
   writer.writeCharacters(emp.getSalary().toString());
   writer.writeEndElement();
   writer.writeEndElement();

   System.out.println(sw.getBuffer().toString());

  } catch (XMLStreamException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

 }
}

package com.xml;

import java.io.StringWriter;

import java.math.BigDecimal;

import javax.xml.stream.XMLOutputFactory;

import javax.xml.stream.XMLStreamException;

import javax.xml.stream.XMLStreamWriter;

public class StaxProcessing {

public static void main(String[] args) {

XMLOutputFactory factory = XMLOutputFactory.newInstance();

// construct employee object

Employee emp = new Employee();

emp.setName("Peter");

emp.setType("first");

emp.setAge(25);

emp.setSalary(BigDecimal.valueOf(35000.00));

StringWriter sw = new StringWriter();

try {

XMLStreamWriter writer = factory.createXMLStreamWriter(sw);

writer.writeStartDocument();

writer.writeStartElement("Employee");

writer.writeStartElement("name");

writer.writeAttribute("type", "first");

writer.writeCharacters(emp.getName());

writer.writeEndElement();

writer.writeStartElement("age");

writer.writeCharacters(new Integer(emp.getAge()).toString());

writer.writeEndElement();

writer.writeStartElement("salary");

writer.writeCharacters(emp.getSalary().toString());

writer.writeEndElement();

System.out.println(sw.getBuffer().toString());

} catch (XMLStreamException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

Output:

<?xml version="1.0" ?>
<Employee><name type="first">Peter</name><age>25</age><salary>35000.0</salary></Employee>

<?xml version="1.0" ?>

<Employee><name type="first">Peter</name><age>25</age><salary>35000.0</salary></Employee>

Here is a simple example to … Read more ›...

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Java OpenCSV tutorial to work with CSV files

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Java project with packages & jar file dependency without an IDE & build tool tutorial

Step 1: Create the following folders

1. c:\projects\learn-java is the “project folder“.

2. com\mycompany1\main & com\mycompany1\service are the “packages” under the project.

…

javap for debugging and better understanding some Java concepts with 3 practical examples

The javap is a class file dissembler. Here are 3 scenarios you can put javap to use with code examples.

#1 Finding the Java version of the class file within a jar

Extract a class file say “MyJobRunner.class” from a jar file and use javap to find out the version used

bash-3.2$ javap -v MyJobRunner

Compiled from "MyJobRunner.java"
public interface com.myapp.invoke.MyJobRunner
  SourceFile: "MyJobRunner.java"
  RuntimeVisibleAnnotations: length = 0x6
   00 01 00 08 00 00
  minor version: 0
  major version: 51
  Constant pool:
const #1 = class        #9;     //  com/myapp/invoke/MyJobRunner
const #2 = class        #10;    //  java/lang/Object
const #3 = Asciz        executeIlliquidDecsProcess;
const #4 = Asciz        ()V;
const #5 = Asciz        SourceFile;
const #6 = Asciz        MyJobRunner.java;
const #7 = Asciz        RuntimeVisibleAnnotations;
const #8 = Asciz        Lorg/springframework/stereotype/Service;;
const #9 = Asciz        com/myapp/invoke/MyJobRunner;
const #10 = Asciz       java/lang/Object;

{
public abstract void executeIlliquidDecsProcess();

}

bash-3.2$ javap -v MyJobRunner

Compiled from "MyJobRunner.java"

public interface com.myapp.invoke.MyJobRunner

SourceFile: "MyJobRunner.java"

RuntimeVisibleAnnotations: length = 0x6

00 01 00 08 00 00

minor version: 0

major version: 51

Constant pool:

const #1 = class #9; // com/myapp/invoke/MyJobRunner

const #2 = class #10; // java/lang/Object

const #3 = Asciz executeIlliquidDecsProcess;

const #4 = Asciz ()V;

const #5 = Asciz SourceFile;

const #6 = Asciz MyJobRunner.java;

const #7 = Asciz RuntimeVisibleAnnotations;

const #8 = Asciz Lorg/springframework/stereotype/Service;;

const #9 = Asciz com/myapp/invoke/MyJobRunner;

const #10 = Asciz java/lang/Object;

{

public abstract void executeIlliquidDecsProcess();

}

“major version: 51”

…

1 2 »

Blog Archives

02: Java 8 Streams, lambdas, intermediate vs terminal ops, and lazy loading with simple examples

BeanIO Java tutorial

Debugging like a pro with eclipse IDE tutorial for Java developers

Java and JAXB Tutorial – Marshaling

Java and JAXB tutorial – unmarshalling

Java and JSON tutorial with Jackson library

Java and XML tutorial with DOM Parser

Java and XML tutorial with SAX parser – reading only

Java and XML tutorial with StAX parser – reading

Java and XML tutorial with Stax Parser – writing cursor based and iterator based

Java OpenCSV tutorial to work with CSV files

Java project with packages & jar file dependency without an IDE & build tool tutorial

javap for debugging and better understanding some Java concepts with 3 practical examples

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