Visitor Pattern

design-pattern/src/Visitor/Application.java

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+package Visitor;
+
+import java.util.ArrayList;
+
+public class Application {
+    public static void main(String[] args) {
+
+        ArrayList<Visitable> visitables = new ArrayList<Visitable>();
+        visitables.add(new VisitableA(1));
+        visitables.add(new VisitableA(2));
+        visitables.add(new VisitableA(3));
+        visitables.add(new VisitableA(4));
+        visitables.add(new VisitableA(5));
+
+        Visitor visitor = new VisitorA();
+
+        for (Visitable visitable: visitables) {
+            visitable.accept(visitor);
+        }
+
+        System.out.println(((VisitorA)visitor).getAgeSum());
+    }
+}

design-pattern/src/Visitor/Visitable.java

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+package Visitor;
+
+public interface Visitable {
+    void accept(Visitor visitor);
+}

design-pattern/src/Visitor/VisitableA.java

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+package Visitor;
+
+public class VisitableA implements Visitable{
+
+    private int age;
+
+    public VisitableA(int age) {
+        this.age = age;
+    }
+
+    @Override
+    public void accept(Visitor visitor) {
+        visitor.visit(this);
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+}

design-pattern/src/Visitor/Visitor

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+Visitor Pattern
+ - 객체에서 처리 분리하기

design-pattern/src/Visitor/Visitor.java

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+package Visitor;
+
+public interface Visitor {
+    void visit(Visitable visitable);
+}

design-pattern/src/Visitor/VisitorA.java

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+package Visitor;
+
+public class VisitorA implements Visitor{
+
+    private int ageSum;
+
+    public VisitorA() {
+        ageSum = 0;
+    }
+
+    @Override
+    public void visit(Visitable visitable) {
+        if(visitable instanceof VisitableA) {
+
+            ageSum += ((VisitableA) visitable).getAge();
+
+        } else {
+
+        }
+    }
+
+    public int getAgeSum() {
+        return ageSum;
+    }
+}