Add supplementary Javadoc

src/main/java/junit/framework/AssertionFailedError.java

@@ -6,10 +6,19 @@
 public class AssertionFailedError extends AssertionError {
 
     private static final long serialVersionUID = 1L;
-
+
+    /**
+     * Constructs a new AssertionFailedError without a detail message.
+     */
     public AssertionFailedError() {
     }
 
+    /**
+     * Constructs a new AssertionFailedError with the specified detail message.
+     * A null message is replaced by an empty String.
+     * @param message the detail message. The detail message is saved for later 
+     * retrieval by the {@code Throwable.getMessage()} method.
+     */
     public AssertionFailedError(String message) {
         super(defaultString(message));
     }

src/main/java/junit/framework/TestFailure.java

@@ -5,7 +5,7 @@
 
 
 /**
- * A <code>TestFailure</code> collects a failed test together with
+ * A {@code TestFailure} collects a failed test together with
  * the caught exception.
  *
  * @see TestResult
@@ -14,7 +14,6 @@ public class TestFailure {
     protected Test fFailedTest;
     protected Throwable fThrownException;
 
-
     /**
      * Constructs a TestFailure with the given test and exception.
      */
@@ -44,18 +43,30 @@ public Throwable thrownException() {
     public String toString() {
         return fFailedTest + ": " + fThrownException.getMessage();
     }
-
+
+    /**
+     * Returns a String containing the stack trace of the error
+     * thrown by TestFailure.
+     */
     public String trace() {
         StringWriter stringWriter = new StringWriter();
         PrintWriter writer = new PrintWriter(stringWriter);
         thrownException().printStackTrace(writer);
         return stringWriter.toString();
     }
 
+    /**
+     * Returns a String containing the message from the thrown exception.
+     */
     public String exceptionMessage() {
         return thrownException().getMessage();
     }
 
+    /**
+     * Returns {@code true} if the error is considered a failure
+     * (i.e. if it is an instance of {@code AssertionFailedError}),
+     * {@code false} otherwise.
+     */
     public boolean isFailure() {
         return thrownException() instanceof AssertionFailedError;
     }