observer pattern

src/main/java/observer/Child.java

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+package observer;
+
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+
+public class Child {
+    private boolean cry = false;
+    private static List<Observer> observers = new ArrayList<>();
+    static {
+        observers.add(new Dad());
+        observers.add(new Mom());
+        observers.add(new Dog());
+    }
+
+    public void weakUp(){
+        System.out.println("child weak up...");
+        WeakUpEvent event = new WeakUpEvent(new Date(), "bed", this);
+        for (Observer observer : observers){
+            observer.actionOnWeakUp(event);
+        }
+        cry = true;
+    }
+
+    public boolean isCry() {
+        return cry;
+    }
+
+    public void setCry(boolean cry) {
+        this.cry = cry;
+    }
+}

src/main/java/observer/Dad.java

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+package observer;
+
+public class Dad implements Observer{
+    public void feed(){
+        System.out.println("Dad feed child...");
+    }
+
+    @Override
+    public void actionOnWeakUp(WeakUpEvent event) {
+        feed();
+    }
+}

src/main/java/observer/Dog.java

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+package observer;
+
+public class Dog implements Observer{
+    public void bark(){
+        System.out.println("Dog barking...");
+    }
+
+    @Override
+    public void actionOnWeakUp(WeakUpEvent event) {
+        bark();
+    }
+}

src/main/java/observer/Main.java

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+package observer;
+
+public class Main {
+    public static void main(String[] args) {
+        Child child = new Child();
+        child.weakUp();
+    }
+}

src/main/java/observer/Mom.java

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+package observer;
+
+public class Mom implements Observer{
+    public void hug(){
+        System.out.println("Mom hug child...");
+    }
+
+    @Override
+    public void actionOnWeakUp(WeakUpEvent event) {
+        hug();
+    }
+}

src/main/java/observer/Observer.java

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+package observer;
+
+public interface Observer {
+    void actionOnWeakUp(WeakUpEvent event);
+}

src/main/java/observer/WeakUpEvent.java

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+package observer;
+
+import java.util.Date;
+
+public class WeakUpEvent {
+    private Date time;
+    private String location;
+    private Child source;
+
+    public WeakUpEvent(Date time, String location, Child source) {
+        this.time = time;
+        this.location = location;
+        this.source = source;
+    }
+
+    public Date getTime() {
+        return time;
+    }
+
+    public void setTime(Date time) {
+        this.time = time;
+    }
+
+    public String getLocation() {
+        return location;
+    }
+
+    public void setLocation(String location) {
+        this.location = location;
+    }
+
+    public Child getSource() {
+        return source;
+    }
+}