development-notes.md

OOPC

• Objects - Entity with state & Behavior
• Class - Bluepring of object
• Inheritance - inherits properties from parents
• Polymorphism - method overloading / overriding
• Abstraction - Abstract/interface to hide details
• Encapsulation - wrapping data into single unit

OOPs Terms

• Coupling - Knowledge of another class or dependency
• Cohesion - single well defined task
• Association - One to One, One to Many, Many to One and Many to Many
• Aggregation - has-a or is part of relation between classes
• Composition - class contains another class as its state

SOLID Principals

• S - Single Responsibility Principal
• O - Open-close Principal
• L - Liskov Substitution method (can be replaced with base class)
• I - Interface Segregation Principal (have as many interface)
• D - Dependency Inversion Principal(depend on inface not concrete class)

Collections

• Collection
  • List
    • ArrayList
    • LinkedList
    • Vector
    • Stack
  • Queue
    • Dequeue
      • ArrayDeque
    • PriorityQueue
  • Set
    • HashSet
    • LinkedHashSet
    • SortedSet
      • TreeSet
• Map
  • HashMap
  • Hastable
  • TreeMap

Data Structures

• Liner
  • Array
    • 1d
    • 2d
    • 3d
  • Stack - LIFO
  • Queue - FIFO
• Non-linear
  • Tree
  • Graphs
  • Sets

Algo

• Bubble sort

Java 8

Generics

• Generics means parameterized types

  class Test<T> {
      T obj;
      Test(T o) {
          this.obj = o;
      }
      public T get(){
          return this.obj;
      }

      //Uses
      Test<Integer> iObj = new Test<Integer>(15);
 }

Lambda

• short block of code which takes in parameters and returns a value

  parameter -> expression
  (parameter1, parameter2) -> expression
  (parameter1, parameter2) -> { code block }

Functional Interfaces

• contains only one abstract method
• @FunctionalInterface

  new Thread(new Runnable() {
      @Override
      public void run() {
          System.out.println("asas");
      }
  });

• Consumer - Takes value(1/2) returns nothing
  • Bi-consumer

      Consumer<Integer> consumer = (value) -> System.out.println(value);
      Consumer<Integer,String> consumer = (val1, val2) -> System.out.println(val2 + val1 );

• Predicate - Retuns boolean
  • Bi-predicate

      Predicate<Integer> isGreaterThanZero = (val) -> val > 0;
      Predicate<Integer, Integer> isGreaterThan = (val1, val2) -> val1 > val2;
  
      // Uses
      isGreaterThanZero.test(100);

• Function
  • Bi-function

  @FunctionalInterface
  public interface BiFunction<T, U, R> 
  {
      R apply(T t, U u);
  }

• Supplier

      @FunctionalInterface
      public interface Supplier<T>{
          T.get();
      }

Optional

```java
Optional<String> empty = Optional.empty();
Optional<String> opt = Optional.of(name);
opt.isPresent()
Optional<String> opt = Optional.ofNullable(name);
Optional<String> opt = Optional.of("ayu");
opt.ifPresent(name -> System.out.println(name.length()));
String nullName = null;
String name = Optional.ofNullable(nullName).orElse("john");
```

Streams

Stream<String> streamEmpty = Stream.empty();
Stream<String> stream = Stream.of(list);
Stream.iterate(40, n -> n + 2).limit(20);
Stream.generate(() -> "element").limit(10);
IntStream.range(1, 3);

Design patterns

• Creational Patterns
  • Factory design pattern
    • Creation logic is hidden
    • One class is responsible to create objects of different types
  • Builder design
    • static Builder class
  • Prototype design
  • Singleton design
• Structural Patterns
  • Adaptor design
    • lets incompatible objects collaborate
  • Facade design
  • Proxy design
    • represents functionality of another class
• Behavioural Patterns
  • Command pattern
  • Iterator pattern
  • Observer pattern
  • Strategy pattern

Multithreding

Executor Framework

Fork and Join

Messaging Queue

Database

Data Modeling

Database Isolation

Profiler - Java

Garbage Collection

JVM

Logical Views

Sequential Views

Application Layring

NFR- Non functional Requirement

• Performance
• Latency
• Avalability
• Depoyment time
• etc

Testing(Unit testing tools, TTD)

Quality Plugin

• Sonarcube

Jenkins

Docker

Kubernaties

Logging Tools

• E = Elasticsearch
  • Log everthing, json based search, indexing
• L = Logstash
  • Data aggregation and processing
• K = Kibana
  • Analysis & visualization

Cloud

Serverless

- AWS Lambda

Storage Services

- AWS s3
- Azureit

Events

Notifictions

Microservices

API Gateway

API Security

Authentication

REST Pricipals

OAS Consumers/Producers

Error Handling

Filteration

Patterns(Euraka, Netflix, Zuul, Circuit Breaking)

Memcaching

Elastic search