简简单单实现观察者模式

1.概念

观察者模式类似于订阅一样，只要订阅了就能收到目标的变化通知。

 2.go

package alian

import "fmt"

type Observer interface {
	update()
}

type Subject struct {
	observers []*Observer
	status int
}
func (this * Subject)registry  (observer *Observer){
	this.observers = append(this.observers , observer)
}
func (this * Subject)unRegistry  (observer *Observer){
	for i := range this.observers{
		if this.observers[i] == observer{
			this.observers =  append(this.observers[:i] , this.observers[i+1 :]...)
			return
		}
	}
}
func (this *Subject) notifyALL(){
	for i := range this.observers{
		(*this.observers[i]).update()
	}
}

type BinaryObserver struct {
	subject *Subject
}
func (this * BinaryObserver) update(){
	fmt.Println(fmt.Sprintf("%b" , this.subject.status))
}
type OctalObserver struct {
	subject *Subject
}
func (this * OctalObserver) update(){
	fmt.Println(fmt.Sprintf("%o" , this.subject.status))
}

package alian

import (
	"fmt"
	"testing"
)

func Test(t *testing.T) {
	s := &Subject{[]*Observer{} , 10}
	var binary , octal Observer
	binary = &BinaryObserver{s}
	octal = &OctalObserver{s}
	s.registry(&binary)
	s.registry(&octal)
	fmt.Println("test1")
	s.notifyALL()
	fmt.Println("test2")
	s.unRegistry(&binary)
	s.notifyALL()

}

3.Java

/**
 * @program: demo
 * @author: alian
 * @description:
 * @create: 2023-03-29 22:53
 **/

package alian.observer;

import java.util.ArrayList;
import java.util.List;

public class Subject {
    private List<Observer> observers = new ArrayList<>();
    private int state;

    public void attach(Observer observer){
        observers.add(observer);
    }

    public void unAttach(Observer observer){
        observers.remove(observer);
    }

    public void notifyAllObservers(){
        for (Observer observer : observers) {
            observer.update();
        }
    }

    public List<Observer> getObservers() {
        return observers;
    }

    public void setObservers(List<Observer> observers) {
        this.observers = observers;
    }

    public int getState() {
        return state;
    }

    public void setState(int state) {
        this.state = state;
    }
}

/**
 * @program: demo
 * @author: alian
 * @description:
 * @create: 2023-03-29 22:59
 **/

package alian.observer;

public class BinaryObserver extends Observer{

    public BinaryObserver(Subject subject) {
        this.subject = subject;
        subject.attach(this);
    }

    @Override
    public void update() {
        System.out.println( "Binary String: "
                + Integer.toBinaryString( subject.getState() ) );
    }

}

package alian.observer;

public abstract class Observer {
    protected Subject subject;
    public abstract void update();
}

/**
 * @program: demo
 * @author: alian
 * @description:
 * @create: 2023-03-29 23:24
 **/

package alian.observer;

public class OctalObserver extends Observer {
    public OctalObserver(Subject subject) {
        this.subject = subject;
        subject.attach(this);
    }

    @Override
    public void update() {
        System.out.println( "Octal String: "
                + Integer.toOctalString( subject.getState() ) );
    }
}

/**
 * @program: demo
 * @author: alian
 * @description:
 * @create: 2023-03-29 23:25
 **/

package alian.observer;

public class Main {
    public static void main(String[] args) {
        Subject s = new Subject();
        s.setState(10);
        new BinaryObserver(s);
        new OctalObserver(s);
        s.notifyAllObservers();
    }
}