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

@@ -23,16 +23,30 @@ 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);
+        new Thread(unsafe).start();
+        new Thread(unsafe).start();
+        new Thread(unsafe).start();
+        new Thread(unsafe).start();
+        new Thread(unsafe).start();
+
+        SafeCopier safe = new SafeCopier(introduction);
+        new Thread(safe).start();
+        new Thread(safe).start();
+        new Thread(safe).start();
+        new Thread(safe).start();
+        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.
         try {
             Thread.sleep(1000);
-        } catch(InterruptedException e) {
+        } catch (InterruptedException e) {
             System.out.println("MAIN INTERRUPTED");
         }
-
-        // Print out the copied versions here.
+        System.out.println("Unsafe: " + unsafe.copied + "\n\n\n\n\n\n");
+        System.out.println("Safe: " + safe.copied);
     }
 }

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

@@ -1,8 +1,36 @@
 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 {
+
+        ReadWriteLock lock = new ReentrantReadWriteLock();
+
+        public SafeCopier(String toCopy) {
+            super(toCopy);
+        }
+
+        public void run() {
+            lock.writeLock().lock();
+            lock.readLock().lock();
+            try {
+                while (stringIterator.hasNext()) {
+                    copied += stringIterator.next() + " ";
+                }
+            } finally {
+                copied = copied.trim();
+                lock.writeLock().unlock();
+                lock.readLock().unlock();
+            }
+
+        }
+    }
+
+
+

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

@@ -1,5 +1,7 @@
 package io.zipcoder;
 
+import java.util.Iterator;
+
 /**
  * Modify the run function so that the monkeys each grab the next word and write it to the copy.
  */
@@ -10,5 +12,10 @@ public class UnsafeCopier extends Copier {
     }
 
     public void run() {
+        while (stringIterator.hasNext()) {
+                        copied += stringIterator.next() + " ";
+                    }
+                copied = copied.trim();
+
     }
 }