Appearance pattern of design pattern

Come on, Xiao Huang 2021-01-23 12:48:22
appearance pattern design pattern


0x01: Introduction to appearance patterns

Appearance mode ( It's also called facade mode ), Through the appearance of the packaging , Make the application see only appearance objects , You don't see the details of the object , This will undoubtedly reduce the complexity of the application , And improve the maintainability of the program .UML The class diagram is as follows :

image.png

among Facade It's the appearance character , It's also called a facade character , The client can call the methods of this role , This role knows all the functions and responsibilities of the subsystem , Proxy client requests to appropriate subsystem objects ;

Subsystem It's a subsystem role , Can have one or more subsystems at the same time , Each subsystem is not a separate class , It's a collection of classes , The subsystem does not know the presence of facade .

0x02: The realization of appearance pattern

Define subsystems Subsystem

public class SubSystemA {
public void dosomethingA() {
System.out.println("SubSystemA dosomethingA");
}
}
public class SubSystemB {
public void dosomethingB() {
System.out.println("SubSystemB dosomethingB");
}
}

Appearance role Facade

public class Facade {
// The entrusted object
private SubSystemA a;
private SubSystemB b;
public Facade() {
a = new SubSystemA();
b = new SubSystemB();
}
// Methods for external access
public void methodA() {
this.a.dosomethingA();
}
public void methodB() {
this.b.dosomethingB();
}
}

Test code

public class Client {
public static void main(String[] args) {
Facade facade = new Facade();
facade.methodA();
facade.methodB();
}
}

0x03: application

Because programmers are generally paid relatively high , So there's usually a little money . How to manage wealth ? Buy your own stocks ? I can't grasp the business point very well , People often cut leeks . Is there any way to manage wealth ? Buying a fund is a good channel .

Stocks 、 national debt 、 Futures

public class Stock{
// Buy stocks
public void buy() {
System.out.println(" Stocks 1 purchase ");
}
// Selling shares
public void sell() {
System.out.println(" Stocks 1 sell ");
}
}
public class NationalDebt{
// Buy national debt
public void buy() {
System.out.println(" national debt 1 purchase ");
}
// Selling Treasury bonds
public void sell() {
System.out.println(" national debt 1 sell ");
}
}
public class Futures{
// Buy futures
public void buy() {
System.out.println(" futures 1 purchase ");
}
// Sell futures
public void sell() {
System.out.println(" futures 1 sell ");
}
}

Funds

The fund manager acts as an intermediary through this class , We can accept investors' funds , Unify on stocks 、 national debt 、 Futures are purchased and redeemed .

public class Fund {
private Stock stock;
private NationalDebt nationalDebt;
private Futures futures;
public Fund() {
stock = new Stock(); // To configure 30%
nationalDebt = new NationalDebt(); // To configure 60%
futures = new Futures(); // To configure 20%
}
// Purchase fund
public void buyFund() {
stock.buy();
nationalDebt.buy();
futures.buy();
}
// Redemption fund
public void sellFund() {
stock.sell();
nationalDebt.sell();
futures.sell();
}
}

Above this is a fund , It's equipped with 30% Shares +60% The national debt +20% futures .

Programmers buy and redeem fund operations

public class Client {
public static void main(String[] args) {
Fund fund = new Fund();
// Fund purchases
fund.buyFund();
System.out.println("》》》》》》》》》》》》");
// Fund redemption
fund.sellFund();
}
}

In this case , I'm not afraid of cutting leeks in stock market any more .

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