Gregg Roeten


Over 1000 Java Questions with Answers, Java code examples, Java diagrams
This site focuses on Languages, Troubleshooting and Debugging, Algorithms, Java, Continuous Integration, tools, Frameworks, IDE's, Platforms, Servers.

Java questions and answers.  Do you want to be a better Java Programmer?  How to code in Java?  How to program in Java?  Beginner Java.  Advanced Java.

Java Interview Question and Answer section
Java Interview Questions I faced in 2017 and 2018
Java8 Interfaces Example
Find Duplicate Number Algorithm Example
Find Top Two Numbers In Array Example
Java General Questions and Answers - Over 150 total
Java Core Interview Questions and Answers, over 135 total
Java Interview Questions and Answers, over 500 total
Java Interview Puzzles, Algorithms, Data Structures, Plus Over 300 Questions and Answers
What is JDBC Plus Questions and Answers

Java Classes Methods section
What are Java Abstract Methods?  What are Java Classes?  What is DRY pdf
What is the difference between Java Abstract and Interface?  Comparison chart for Abstract and Interface
What is a Java Anonymous Inner Class?
What are Java Constructors, Default, Parameterized, Overloading, Copy Plus over 33 Questions and Answers
What are Java Enums
What is the Java Mock Stub differences
What are Java Exceptions, Checked, Unchecked, Errors, Throw, Throws, 50 Questions and Answers
What is a Java Interface, Implement, Extend, Default Method, Multiple Inheritance with Questions and Answers
How to read and write Java Byte Streams
What is the Java ClassLoader
How does Java read data into a Class Object
What is the Java Serializable Interface

Java OOPs
What are OOPs in brief Polymorphism Inheritance Encapsulation Abstraction
What are OOPs Concepts

Java Strings section
What are Java Strings, StringBuffer, StringBuilder
What is the Java String Pool Memory

Java Memory section
What is Java Memory Management, 37 pgs.
What is the Java Stack, Heap, Garbage Collection
What is Java Reference Instance Variable Stack Heap Memory

Java Collection section
What is the Java Collection Framework Set Queue List Map, Plus over 75 Questions and Answers
What are the differences between HashSet, HashMap, HashTable, ConcurrentHashMap, TreeSet, Comparison chart , Plus over 112 Q and A
How does Java Instantiate a List

Java Syntax CheatSheets
Java Cheat-Sheet, 18 pgs.
Java Collections Cheat Sheet, Comparison Chart, Interfaces, Descriptions
What is Java's Basic Syntax, 22 pgs.

What is a brief description of the differences between JSON and XML
How to use Java to encode decode JSON, code example
What are the differences between JSON and XML

Java API's
What are Enterprise Java Beans Plus Questions and Answers
How does JDBC Process SQL Statements
What is the JMS Java Message Service
What is JSP Java Server Pages, 25 pgs
What is Java Persistence API
What is Java Transaction Management

Java Misc section
What is Java Assert, or Assertions?
What are the Java Best Practices, Multithreading, Automate, Coding, Review, Design, I/O, Factoring, Architecture, 7 pgs.
What are the java APIs Servlets JSP EJB JSF Tiers Containers, 43 pgs.
Following is a list of Java Application Development Tips and Tricks
What is the Java Commandline classpath problem
What are the Design Patterns Singleton and Factory
What are the Top 4 Design Patterns
What are Java Short Circuit Operators Bitwise Operators
Java 8 Tutorial
What is Java Multithread, Concurrency, Serializable, Synchronized, Mutex, Semaphore, fail-fast Iterator, over 160 Questions and Answers
What are the Java8 features
What is a Java Portlet
What is the Java Distribution MultiTier Application Container

Other areas:
Drop Down Menus: Each PDF file has a table of contents at the beginning.
Following are examples of Work Experience Projects

Created ython Django Architecture Diagram from a work related project

Created Microsoft Active Directory Diagram during MCSE certification

Created HTTP Web Container J2EE JSP ServletSQL diagram

Created JSF Web Application Server with AJAX messages diagram

Created Typical firewall and gateway network diagram

Following pdf files are examples from Recent Personal Projects, Tutorials

Created Project Simple Spring MVC BeanMapping Netbeans8 ApacheTomcat

Created Project Spring MVC RESTful PersistenceDB Netbeans8 ApacheTomcat

Created Project RESTful Web Services JAXRS DB TestResourceBeans Javascript NetBeans8

Created Project RESTful Web-Service Test RESTful Web Services

Created Project Simple WebService Application NetBeans8

Created Project MeanStack MongoDB Express.js Angular4 Node.js Project

Created Project Web Application using Hibernate Framework ORM Java7 JSF2 Glassfish server in Netbeans8

This site was created with HTML5 and CSS2.1