Assignment No.12 first complete implementation.

1 files changed, 132 insertions, 0 deletions

diff --git a/src/de/fhswf/in/inf/java1/aufgabe12/UPN.java b/src/de/fhswf/in/inf/java1/aufgabe12/UPN.java
new file mode 100644
index 0000000..815e937
--- /dev/null
+++ b/src/de/fhswf/in/inf/java1/aufgabe12/UPN.java
@@ -0,0 +1,132 @@
+/**
+ * 
+ */
+package de.fhswf.in.inf.java1.aufgabe12;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Stack;
+
+/**
+ * A class that calculates in UPN.
+ *
+ * @author $Author: $
+ * @version $Revision: $, $Date: $ UTC
+ */
+public class UPN
+{
+
+   private Stack<Double> upnStack = new Stack<>();
+
+   private static Map<String, Operator> operators = new HashMap<>();
+
+   static
+   {
+      operators.put("+", new Addition());
+      operators.put("-", new Subtraction());
+      operators.put("*", new Multiplication());
+      operators.put("/", new Division());
+      operators.put("%", new Modulo());
+   }
+
+   /**
+    * Empty constructor.
+    *
+    */
+   public UPN()
+   {
+   }
+
+   /**
+    * Reads a string and puts it on the UPN upnStack.
+    *
+    * @param upnString
+    *           A space delimited string in UPN notation.
+    */
+   public final void calculate(String upnString)
+   {
+      if (upnString == null)
+      {
+         throw new IllegalArgumentException("UpnString can't be null.");
+      }
+      if (upnString.isEmpty())
+      {
+         throw new IllegalArgumentException("UpnString can't be empty.");
+      }
+
+      for (String string : upnString.split("\\s+"))
+      {
+         if (!string.isEmpty())
+         {
+            Operator operator = operators.get(string);
+
+            if (operator == null)
+            {
+               try
+               {
+                  operator = new UnaryTemplate(string);
+               }
+               catch (IllegalArgumentException e)
+               {
+                  if (!(e.getCause() instanceof NoSuchMethodException))
+                  {
+                     throw e;
+                  }
+               }
+               if (operator == null)
+               {
+                  try
+                  {
+                     operator = new BinaryTemplate(string);
+                  }
+                  catch (IllegalArgumentException e)
+                  {
+                     if (!(e.getCause() instanceof NoSuchMethodException))
+                     {
+                        throw e;
+                     }
+                  }
+
+               }
+               if (operator != null)
+               {
+                  operators.put(string, operator);
+                  operator.eval(upnStack);
+               }
+               else
+               {
+                  try
+                  {
+                     upnStack.add(Double.valueOf(string));
+                  }
+                  catch (NumberFormatException e)
+                  {
+                     throw new IllegalArgumentException("String: \"" + string
+                           + "\" is not a valid"
+                           + " operator nor a valid operand.");
+                  }
+               }
+            }
+            else
+            {
+               operator.eval(upnStack);
+            }
+         }
+      }
+   }
+
+   /**
+    * Get the result of a calculation done before.
+    *
+    * @return The top most value on the UPN stack.
+    */
+   public final double getResult()
+   {
+      if (upnStack.empty())
+      {
+         throw new IllegalArgumentException("UPN stack is empty.");
+      }
+      return upnStack.peek();
+   }
+
+}