MessageDigest: Rework odd toString implementation.

It's cleaner and more idiomatic to use a StringBuilder instead
of a PrintWriter and ByteArrayOutputStream.toString.

Change-Id: I48291fe5b835754d0d52adba9a08da18f77bf821
diff --git a/ojluni/src/main/java/java/security/MessageDigest.java b/ojluni/src/main/java/java/security/MessageDigest.java
index d1fe343..a19fb85 100755
--- a/ojluni/src/main/java/java/security/MessageDigest.java
+++ b/ojluni/src/main/java/java/security/MessageDigest.java
@@ -403,19 +403,22 @@
      * Returns a string representation of this message digest object.
      */
     public String toString() {
-        ByteArrayOutputStream baos = new ByteArrayOutputStream();
-        PrintStream p = new PrintStream(baos);
-        p.print(algorithm+" Message Digest from "+provider.getName()+", ");
+        StringBuilder builder = new StringBuilder();
+        builder.append(algorithm);
+        builder.append(" Message Digest from ");
+        builder.append(provider.getName());
+        builder.append(", ");
+
         switch (state) {
         case INITIAL:
-            p.print("<initialized>");
+            builder.append("<initialized>");
             break;
         case IN_PROGRESS:
-            p.print("<in progress>");
+            builder.append("<in progress>");
             break;
         }
-        p.println();
-        return (baos.toString());
+
+        return builder.toString();
     }
 
     /**