Correct javadoc of the hash function signature.

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/HashFunction.java

@@ -30,4 +30,20 @@ public interface HashFunction extends HashFunctionIdentity {
      * @return the long value of the hash.
      */
     long apply(byte[] buffer, int seed);
+
+    /**
+     * Gets the signature of this function.
+     *
+     * <p>The signature of this function is calculated as:
+     * <pre><code>
+     * int seed = 0;
+     * apply(String.format("%s-%s-%s",
+     *                     getName().toUpperCase(Locale.ROOT), getSignedness(), getProcess())
+     *             .getBytes("UTF-8"), seed);
+     * </code></pre>
+     *
+     * @see HashFunctionIdentity#prepareSignatureBuffer(HashFunctionIdentity)
+     */
+    @Override
+    long getSignature();
 }

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/HashFunctionIdentity.java

@@ -98,16 +98,18 @@ public interface HashFunctionIdentity {
     }
 
     /**
-     * Gets the signature buffer for a HashFunctionIdentity.
+     * Gets a {@code byte[]} buffer for a HashFunctionIdentity to create a signature. The
-     * <p>
+     * {@code byte[]} is composed using properties of the hash function as:
-     * The signature of this function is calculated as:
+     *
-     * {@code
+     * <pre><code>
-     * apply( String.format( "%s-%s-%s", getName().toUpperCase( Locale.ROOT ), getSignedness(), getProcess() )
+     * String.format("%s-%s-%s",
-     *     .getBytes( "UTF-8" ), 0 );
+     *               getName().toUpperCase(Locale.ROOT), getSignedness(), getProcess())
-     * }
+     *       .getBytes("UTF-8");
-     * </p>
+     * </code></pre>
+     *
      * @param identity The HashFunctionIdentity to create the buffer for.
      * @return the signature buffer for the identity
+     * @see #getSignature()
      */
     static byte[] prepareSignatureBuffer(final HashFunctionIdentity identity) {
         return String.format("%s-%s-%s",
@@ -144,13 +146,13 @@ public interface HashFunctionIdentity {
     String getProvider();
 
     /**
-     * Gets the signature of this function. <p> The signature of this function is
+     * Gets the signature of this function. The signature is the output of the hash function
-     * calculated as: {@code
+     * when applied to a set of bytes composed using properties of the hash function.
-     * apply( String.format( "%s-%s-%s", getName(), getSignedness(), getProcess() )
+     *
-     *     .getBytes( "UTF-8" ), 0 );
+     * <p>Implementations should define the method used to generate the signature.
-     * } </p>
      *
      * @return the signature of this function.
+     * @see #prepareSignatureBuffer(HashFunctionIdentity)
      */
     long getSignature();