add code

code/Design_Pattern/观察者模式/CurrentConditionsDisplay.java

@@ -0,0 +1,13 @@
+package Design_Pattern.观察者模式;
+
+public class CurrentConditionsDisplay implements Observer {
+
+    public CurrentConditionsDisplay(Subject weatherData) {
+        weatherData.registerObserver(this);
+    }
+
+    @Override
+    public void update(float temp, float humidity, float pressure) {
+        System.out.println("CurrentConditionsDisplay.update: " + temp + " " + humidity + " " + pressure);
+    }
+}

code/Design_Pattern/观察者模式/Observer.java

@@ -0,0 +1,6 @@
+package Design_Pattern.观察者模式;
+
+public interface Observer {
+    //温度、湿度、压强
+    void update(float temp,float humidity,float pressure);
+}

code/Design_Pattern/观察者模式/StatisticsDisplay.java

@@ -0,0 +1,13 @@
+package Design_Pattern.观察者模式;
+
+public class StatisticsDisplay implements Observer {
+
+    public StatisticsDisplay(Subject weatherData) {
+        weatherData.registerObserver(this);
+    }
+
+    @Override
+    public void update(float temp, float humidity, float pressure) {
+        System.out.println("StatisticsDisplay.update: " + temp + " " + humidity + " " + pressure);
+    }
+}

code/Design_Pattern/观察者模式/Subject.java

@@ -0,0 +1,7 @@
+package Design_Pattern.观察者模式;
+
+public interface Subject {
+    void registerObserver(Observer o);
+    void removeObserver(Observer o);
+    void notifyObserver();
+}

code/Design_Pattern/观察者模式/WeatherData.java

@@ -0,0 +1,42 @@
+package Design_Pattern.观察者模式;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class WeatherData implements Subject {
+    private List<Observer> observers;
+    private float temperature;
+    private float humidity;
+    private float pressure;
+
+    public WeatherData() {
+        observers = new ArrayList<>();
+    }
+
+    public void setMeasurements(float temperature, float humidity, float pressure) {
+        this.temperature = temperature;
+        this.humidity = humidity;
+        this.pressure = pressure;
+        notifyObserver();
+    }
+
+    @Override
+    public void registerObserver(Observer o) {
+        observers.add(o);
+    }
+
+    @Override
+    public void removeObserver(Observer o) {
+        int i = observers.indexOf(o);
+        if (i >= 0) {
+            observers.remove(i);
+        }
+    }
+
+    @Override
+    public void notifyObserver() {
+        for (Observer o : observers) {
+            o.update(temperature, humidity, pressure);
+        }
+    }
+}

code/Design_Pattern/观察者模式/WeatherStation.java

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+package Design_Pattern.观察者模式;
+
+public class WeatherStation {
+    public static void main(String[] args) {
+        WeatherData weatherData = new WeatherData();
+        CurrentConditionsDisplay currentConditionsDisplay = new CurrentConditionsDisplay(weatherData);
+        StatisticsDisplay statisticsDisplay = new StatisticsDisplay(weatherData);
+
+        weatherData.setMeasurements(0, 0, 0);
+        weatherData.setMeasurements(1, 1, 1);
+    }
+}