From 9361cb23a1ab1744e13d480274ecb586b9610139 Mon Sep 17 00:00:00 2001
From: Stefan Suhren <suhren.stefan@fh-swf.de>
Date: Wed, 17 Dec 2014 15:11:07 +0100
Subject: Assignment No.12 implements interface and abstract classes

---
 .../in/inf/java1/aufgabe12/BinaryOperator.java     | 51 ++++++++++++++++++++++
 src/de/fhswf/in/inf/java1/aufgabe12/Operator.java  | 24 ++++++++++
 .../in/inf/java1/aufgabe12/UnaryOperator.java      | 46 +++++++++++++++++++
 3 files changed, 121 insertions(+)
 create mode 100644 src/de/fhswf/in/inf/java1/aufgabe12/BinaryOperator.java
 create mode 100644 src/de/fhswf/in/inf/java1/aufgabe12/Operator.java
 create mode 100644 src/de/fhswf/in/inf/java1/aufgabe12/UnaryOperator.java

diff --git a/src/de/fhswf/in/inf/java1/aufgabe12/BinaryOperator.java b/src/de/fhswf/in/inf/java1/aufgabe12/BinaryOperator.java
new file mode 100644
index 0000000..ef007bd
--- /dev/null
+++ b/src/de/fhswf/in/inf/java1/aufgabe12/BinaryOperator.java
@@ -0,0 +1,51 @@
+/**
+ * 
+ */
+package de.fhswf.in.inf.java1.aufgabe12;
+
+import java.util.Stack;
+
+/**
+ * An abstract class for calculations with unary operators.
+ *
+ * @author $Author: $
+ * @version $Revision: $, $Date: $ UTC
+ */
+public abstract class BinaryOperator implements Operator
+{
+   /*
+    * (non-Javadoc)
+    * 
+    * @see de.fhswf.in.inf.java1.aufgabe12.Operator#eval(java.util.Stack)
+    */
+   @Override
+   public final void eval(Stack<Double> stack)
+   {
+      if (stack == null)
+      {
+         throw new IllegalArgumentException("Stack must not be null.");
+      }
+
+      if (stack.size() < 2)
+      {
+         throw new IllegalArgumentException(
+               "Unary operation requires one operand.");
+      }
+
+      double d2 = stack.pop();
+      double d1 = stack.pop();
+
+      stack.push(eval(d1, d2));
+   }
+
+   /**
+    * This class implements the calculation.
+    *
+    * @param d1
+    *           The first operator.
+    * @param d2
+    *           The second operator.
+    * @return The result of the calculation.
+    */
+   abstract double eval(double d1, double d2);
+}
diff --git a/src/de/fhswf/in/inf/java1/aufgabe12/Operator.java b/src/de/fhswf/in/inf/java1/aufgabe12/Operator.java
new file mode 100644
index 0000000..3edb805
--- /dev/null
+++ b/src/de/fhswf/in/inf/java1/aufgabe12/Operator.java
@@ -0,0 +1,24 @@
+/**
+ * 
+ */
+package de.fhswf.in.inf.java1.aufgabe12;
+
+import java.util.Stack;
+
+/**
+ * An interface for on UPN operator.
+ *
+ * @author $Author: $
+ * @version $Revision: $, $Date: $ UTC
+ */
+public interface Operator
+{
+   /**
+    * Gets a stack of doubles and calculates a new value to be put on the
+    * stack.
+    *
+    * @param stack
+    *           The UPN stack of the calculator.
+    */
+   void eval(Stack<Double> stack);
+}
diff --git a/src/de/fhswf/in/inf/java1/aufgabe12/UnaryOperator.java b/src/de/fhswf/in/inf/java1/aufgabe12/UnaryOperator.java
new file mode 100644
index 0000000..481c027
--- /dev/null
+++ b/src/de/fhswf/in/inf/java1/aufgabe12/UnaryOperator.java
@@ -0,0 +1,46 @@
+/**
+ * 
+ */
+package de.fhswf.in.inf.java1.aufgabe12;
+
+import java.util.Stack;
+
+/**
+ * An abstract class for calculations with unary operators.
+ *
+ * @author $Author: $
+ * @version $Revision: $, $Date: $ UTC
+ */
+public abstract class UnaryOperator implements Operator
+{
+   /*
+    * (non-Javadoc)
+    * 
+    * @see de.fhswf.in.inf.java1.aufgabe12.Operator#eval(java.util.Stack)
+    */
+   @Override
+   public final void eval(Stack<Double> stack)
+   {
+      if (stack == null)
+      {
+         throw new IllegalArgumentException("Stack must not be null.");
+      }
+
+      if (stack.size() < 1)
+      {
+         throw new IllegalArgumentException(
+               "Unary operation requires one operand.");
+      }
+      
+      stack.push(eval(stack.pop()));
+   }
+
+   /**
+    * This class implements the calculation.
+    *
+    * @param d
+    *           The unary operator.
+    * @return The result of the calculation.
+    */
+   abstract double eval(double d);
+}
-- 
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