first commit

Semester 1/Programming 1/Java/examples/projects/chapter03/mail-system/MailServer.java

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+import java.util.ArrayList;
+import java.util.List;
+import java.util.Iterator;
+
+/**
+ * A simple model of a mail server. The server is able to receive
+ * mail items for storage, and deliver them to clients on demand.
+ * 
+ * @author David J. Barnes and Michael Kölling
+ * @version 2016.02.29
+ */
+public class MailServer
+{
+    // Storage for the arbitrary number of mail items to be stored
+    // on the server.
+    private List<MailItem> items;
+
+    /**
+     * Construct a mail server.
+     */
+    public MailServer()
+    {
+        items = new ArrayList<>();
+    }
+
+    /**
+     * Return how many mail items are waiting for a user.
+     * @param who The user to check for.
+     * @return How many items are waiting.
+     */
+    public int howManyMailItems(String who)
+    {
+        int count = 0;
+        for(MailItem item : items) {
+            if(item.getTo().equals(who)) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    /**
+     * Return the next mail item for a user or null if there
+     * are none.
+     * @param who The user requesting their next item.
+     * @return The user's next item.
+     */
+    public MailItem getNextMailItem(String who)
+    {
+        Iterator<MailItem> it = items.iterator();
+        while(it.hasNext()) {
+            MailItem item = it.next();
+            if(item.getTo().equals(who)) {
+                it.remove();
+                return item;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Add the given mail item to the message list.
+     * @param item The mail item to be stored on the server.
+     */
+    public void post(MailItem item)
+    {
+        items.add(item);
+    }
+}