JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Design Pattern Introduction

A design pattern is a general reusable solution to a commonly occurring problem within a given context in software design. A design pattern is not a finished design that can be transformed directly into source or machine code. It is a description or template for how to solve a problem that can be used in many different situations. Patterns are formalized best practices that the programmer must implement in the application. Object-oriented design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Patterns that imply object-orientation or more generally mutable state, are not as applicable in functional programming languages.

The types of design patterns are Creational, Structural, and Behavioral design patterns.

Creational Design Pattern

Creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. The basic form of object creation could result in design problems or added complexity to the design. Creational design patterns solve this problem by somehow controlling this object creation. Types of creational design patterns are:

  1. Singleton Pattern
  2. Factory Pattern
  3. Abstract Factory Pattern
  4. Builder Pattern
  5. Prototype Pattern

Structural Design Pattern

Structural design patterns are design patterns that ease the design by identifying a simple way to realize relationships between entities.

  1. Adapter Pattern
  2. Composite Pattern
  3. Proxy Pattern
  4. Flyweight Pattern
  5. Facade Pattern
  6. Bridge Pattern
  7. Decorator Pattern

Behavioral Design Pattern

Behavioral design patterns are design patterns that identify common communication patterns between objects and realize these patterns. By doing so, these patterns increase flexibility in carrying out this communication.

  1. Template Method Pattern
  2. Mediator Pattern
  3. Chain of Responsibility Pattern
  4. Observer Pattern
  5. Strategy Pattern
  6. Command Pattern
  7. State Pattern
  8. Visitor Pattern
  9. Iterator Pattern
  10. Memento Pattern

Knowledge Centre
Can we call servlet destory() from service()?
As you know, destory() is part of servlet life cycle methods, it is used to kill the servlet instance. Servlet Engine is used to call destory(). In case, if you call destory method from service(), it just execute the code written in the destory(), but it wont kill the servlet instance. destroy() will be called before killing the servlet instance by servlet engine.
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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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