Chain of Responsibility Pattern

design-pattern/src/ChainOfResponsibility/Calculator.java

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+package ChainOfResponsibility;
+
+abstract public class Calculator {
+
+    private Calculator nextCalculator;
+
+    public void setNextCalculator(Calculator nextCalculator) {
+        this.nextCalculator = nextCalculator;
+    }
+
+    public boolean process(Request request) {
+        if(operator(request)) {
+            return true;
+        } else {
+            if(nextCalculator != null)
+            return nextCalculator.process(request);
+        }
+        return false;
+    }
+
+    abstract protected boolean operator(Request request);
+}

design-pattern/src/ChainOfResponsibility/Chain of Responsibility

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+Chain of Responsibility
+ - 다양한 처리 방식을 유연하게 연결
+
+ - 사칙연산 프로그램

design-pattern/src/ChainOfResponsibility/Main.java

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+package ChainOfResponsibility;
+
+public class Main {
+    public static void main(String[] args) {
+        Calculator plus = new PlusCalculator();
+        Calculator sub = new SubCalculator();
+
+        plus.setNextCalculator(sub);
+        Request request1 = new Request(1, 2, "+");
+        Request request2 = new Request(10, 2, "-");
+
+        plus.process(request1);
+        plus.process(request2);
+    }
+}

design-pattern/src/ChainOfResponsibility/PlusCalculator.java

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+package ChainOfResponsibility;
+
+public class PlusCalculator extends Calculator {
+
+    @Override
+    protected boolean operator(Request request) {
+        if(request.getOperator().equals("+")) {
+            int a = request.getA();
+            int b = request.getB();
+            int result = a + b;
+            System.out.println(a + " + " + b + " = " + result);
+        }
+        return false;
+    }
+}

design-pattern/src/ChainOfResponsibility/Request.java

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+package ChainOfResponsibility;
+
+public class Request {
+
+    private int a, b;
+    private String operator;
+
+    public Request(int a, int b, String operator) {
+        this.a = a;
+        this.b = b;
+        this.operator = operator;
+    }
+
+    public int getA() {
+        return a;
+    }
+
+    public void setA(int a) {
+        this.a = a;
+    }
+
+    public int getB() {
+        return b;
+    }
+
+    public void setB(int b) {
+        this.b = b;
+    }
+
+    public String getOperator() {
+        return operator;
+    }
+
+    public void setOperator(String operator) {
+        this.operator = operator;
+    }
+}

design-pattern/src/ChainOfResponsibility/SubCalculator.java

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+package ChainOfResponsibility;
+
+public class SubCalculator extends Calculator {
+
+    @Override
+    protected boolean operator(Request request) {
+        if(request.getOperator().equals("-")) {
+            int a = request.getA();
+            int b = request.getB();
+            int result = a - b;
+            System.out.println(a + " - " + b + " = " + result);
+        }
+        return false;
+    }
+}