1 files changed, 23 insertions, 6 deletions
diff --git a/src/main/java/org/apache/commons/io/input/MessageDigestCalculatingInputStream.java b/src/main/java/org/apache/commons/io/input/MessageDigestCalculatingInputStream.java
index 7aed4185..97d7ff59 100644
--- a/src/main/java/org/apache/commons/io/input/MessageDigestCalculatingInputStream.java
+++ b/src/main/java/org/apache/commons/io/input/MessageDigestCalculatingInputStream.java
@@ -21,12 +21,13 @@ import java.io.InputStream;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.security.Provider;
+import java.util.Objects;
 
 import org.apache.commons.io.build.AbstractStreamBuilder;
 
 /**
  * This class is an example for using an {@link ObservableInputStream}. It creates its own {@link org.apache.commons.io.input.ObservableInputStream.Observer},
- * which calculates a checksum using a MessageDigest, for example an MD5 sum.
+ * which calculates a checksum using a {@link MessageDigest}, for example, a SHA-512 sum.
  * <p>
  * To build an instance, see {@link Builder}.
  * </p>
@@ -35,12 +36,11 @@ import org.apache.commons.io.build.AbstractStreamBuilder;
  * Cryptography Architecture Standard Algorithm Name Documentation</a> for information about standard algorithm names.
  * </p>
  * <p>
- * <em>Note</em>: Neither {@link ObservableInputStream}, nor {@link MessageDigest}, are thread safe. So is {@link MessageDigestCalculatingInputStream}.
- * </p>
- * <p>
- * TODO Rename to MessageDigestInputStream in 3.0.
+ * <em>Note</em>: Neither {@link ObservableInputStream}, nor {@link MessageDigest}, are thread safe, so is {@link MessageDigestCalculatingInputStream}.
  * </p>
+ * @deprecated Use {@link MessageDigestInputStream}.
  */
+@Deprecated
 public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
     /**
@@ -61,6 +61,9 @@ public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
         private MessageDigest messageDigest;
 
+        /**
+         * Constructs a new Builder.
+         */
         public Builder() {
             try {
                 this.messageDigest = getDefaultMessageDigest();
@@ -92,6 +95,9 @@ public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
         /**
          * Sets the message digest.
+         * <p>
+         * The MD5 cryptographic algorithm is weak and should not be used.
+         * </p>
          *
          * @param messageDigest the message digest.
          */
@@ -101,6 +107,9 @@ public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
         /**
          * Sets the name of the name of the message digest algorithm.
+         * <p>
+         * The MD5 cryptographic algorithm is weak and should not be used.
+         * </p>
          *
          * @param algorithm the name of the algorithm. See the MessageDigest section in the
          *                  <a href= "https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#MessageDigest"> Java Cryptography
@@ -123,9 +132,10 @@ public class MessageDigestCalculatingInputStream extends ObservableInputStream {
          * Constructs an MessageDigestMaintainingObserver for the given MessageDigest.
          *
          * @param messageDigest the message digest to use
+         * @throws NullPointerException if messageDigest is null.
          */
         public MessageDigestMaintainingObserver(final MessageDigest messageDigest) {
-            this.messageDigest = messageDigest;
+            this.messageDigest = Objects.requireNonNull(messageDigest, "messageDigest");
         }
 
         @Override
@@ -187,9 +197,13 @@ public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
     /**
      * Constructs a new instance, which calculates a signature on the given stream, using the given {@link MessageDigest}.
+     * <p>
+     * The MD5 cryptographic algorithm is weak and should not be used.
+     * </p>
      *
      * @param inputStream   the stream to calculate the message digest for
      * @param messageDigest the message digest to use
+     * @throws NullPointerException if messageDigest is null.
      * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}.
      */
     @Deprecated
@@ -200,6 +214,9 @@ public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
     /**
      * Constructs a new instance, which calculates a signature on the given stream, using a {@link MessageDigest} with the given algorithm.
+     * <p>
+     * The MD5 cryptographic algorithm is weak and should not be used.
+     * </p>
      *
      * @param inputStream the stream to calculate the message digest for
      * @param algorithm   the name of the algorithm requested. See the MessageDigest section in the