first attempt

src/main/java/io/zipcoder/MonkeyTypewriter.java

@@ -23,7 +23,15 @@ public class MonkeyTypewriter {
         // Do all of the Monkey / Thread building here
         // For each Copier(one safe and one unsafe), create and start 5 monkeys copying the introduction to
         // A Tale Of Two Cities.
+        UnsafeCopier unsafe = new UnsafeCopier(introduction);
+        for (int i=5; i>0; i--) {
+            new Thread(unsafe).start();
+        }
 
+        SafeCopier safe = new SafeCopier(introduction);
+        for (int i=5; i>0; i--) {
+            new Thread(safe).start();
+        }
 
         // This wait is here because main is still a thread and we want the main method to print the finished copies
         // after enough time has passed.
@@ -34,5 +42,7 @@ public class MonkeyTypewriter {
         }
 
         // Print out the copied versions here.
+        System.out.println("Unsafe version: \n" + unsafe.copied);
+        System.out.println("Safe version: \n" + safe.copied);
     }
 }

src/main/java/io/zipcoder/SafeCopier.java

@@ -1,8 +1,30 @@
 package io.zipcoder;
 
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
 /**
  * Make this extend the Copier like `UnsafeCopier`, except use locks to make sure that the actual intro gets printed
  * correctly every time.  Make the run method thread safe.
  */
-public class SafeCopier {
+public class SafeCopier extends Copier {
+
+    public SafeCopier(String toCopy) {
+        super(toCopy);
+    }
+
+    public void run() {
+        ReadWriteLock lock = new ReentrantReadWriteLock();
+        lock.writeLock().lock();
+        lock.readLock().lock();
+        try {
+            while (stringIterator.hasNext()){
+                copied += stringIterator.next() + " ";
+            }
+        } finally {
+            lock.writeLock().unlock();
+            lock.readLock().unlock();
+        }
+
+    }
 }

src/main/java/io/zipcoder/UnsafeCopier.java

@@ -10,5 +10,10 @@ public class UnsafeCopier extends Copier {
     }
 
     public void run() {
+        while (stringIterator.hasNext()){
+            copied += stringIterator.next() + " ";
+        }
     }
+
+
 }