software development on java language -- 2

I need someone who is export on software development java language, these topics. below....(if you are not sure about the topics than please don't waste my time. I ONLY NEED SOMEBODY WHO KNOWS WELL ABOUT THE SUBJECT AND TOPICS, I only need help for 3 hours )

Streams

map

applies a transformation function on each item in the stream

order matters

filter

pass it a lambda returns true/false, if true, if false it does not continue

order matters

collect

Collect to different type like list, set

Custom Annotation

runtime retention

Reflection

How to get methods, fields, ect

Get an annotation

Lambdas

how to write one

How to pass one

@Functionalinterface

Design Patterns

Builder

.build()

Solves, multiple constructors, long constructors

MyConstructor(null,null,null,null,null,null,null,8,null,null,null,null)

Factory

helps instantiate child class objects

ObjectA factory -> return an object that implements/extends ObjectA

typically there is a switch statement

Singleton

Makes it so there is only one instance of something

Helpful for re-using an object in multiple places

private constructor

Lazy load

don’t instantiate unless necessary

Adapter

basically a wrapper

public method always looks the same

hides implementation details

addItem(T item)

implemented in mongodb

plain List

mysql, aws aurora

text document

DAO

managing data

hides storage code

encapsulates a single data type/related data types

DTO

pojo (Plain old java object)

might leave the current application

java -> js, js ->java, java -> python, java -> java

string, float, arrays, objects, dates

don’t add any logic here

Iterator

helper pointer to the next item in a collection

User doesn’t have to know how it gets the next item

All of the logic for the underlying data source is hidden

next(), getNext(), hasNext()

Observer/State

how do you know when a value has changed?

2 options, check repeatedly, or have a list of the items that want to know when something changed

setters in react, using a setter, it tells all the child components that a value changed

The page knows the second a value changes, does not have to wait

How react state variables work

Interpreter (from compiler)

Program that runs a bytecode on top of a cpu

Visitor (from compiler)

Object that visits nodes in a collection (tree in our case)

Threads

Start a basic thread

extend vs implement

how to join

how to sync a method

Collections

basic types

know how to pick one

Polymorphism

parametric

Make a generic class

subtyping

overriding

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