fix checkstyle violations by adding javadoc

Author: PascalSchumacher

src/main/java/org/apache/commons/io/input/MessageDigestCalculatingInputStream.java

@@ -31,9 +31,16 @@
  */
 public class MessageDigestCalculatingInputStream extends ObservableInputStream {
 
+    /**
+     * Maintains the message digest.
+     */
     public static class MessageDigestMaintainingObserver extends Observer {
         private final MessageDigest md;
 
+        /**
+         * Creates an MessageDigestMaintainingObserver for the given MessageDigest. 
+         * @param pMd the message digest to use
+         */
         public MessageDigestMaintainingObserver(MessageDigest pMd) {
             md = pMd;
         }
@@ -53,6 +60,8 @@ void data(byte[] pBuffer, int pOffset, int pLength) throws IOException {
 
     /** Creates a new instance, which calculates a signature on the given stream,
      * using the given {@link MessageDigest}.
+     * @param pStream the stream to calculate the message digest for
+     * @param pDigest the message digest to use
      */
     public MessageDigestCalculatingInputStream(InputStream pStream, MessageDigest pDigest) {
         super(pStream);
@@ -62,13 +71,18 @@ public MessageDigestCalculatingInputStream(InputStream pStream, MessageDigest pD
 
     /** Creates a new instance, which calculates a signature on the given stream,
      * using a {@link MessageDigest} with the given algorithm.
+     * @param pStream the stream to calculate the message digest for
+     * @param pAlgorithm the name of the algorithm to use
+     * @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
      */
     public MessageDigestCalculatingInputStream(InputStream pStream, String pAlgorithm) throws NoSuchAlgorithmException {
         this(pStream, MessageDigest.getInstance(pAlgorithm));
     }
 
     /** Creates a new instance, which calculates a signature on the given stream,
      * using a {@link MessageDigest} with the "MD5" algorithm.
+     * @param pStream the stream to calculate the message digest for
+     * @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
      */
     public MessageDigestCalculatingInputStream(InputStream pStream) throws NoSuchAlgorithmException {
         this(pStream, MessageDigest.getInstance("MD5"));
@@ -80,6 +94,7 @@ public MessageDigestCalculatingInputStream(InputStream pStream) throws NoSuchAlg
      * This is probably not, what you expect. Make sure, that the complete data has been
      * read, if that is what you want. The easiest way to do so is by invoking
      * {@link #consume()}.
+     * @return the message digest used
      */
     public MessageDigest getMessageDigest() {
         return messageDigest;

src/main/java/org/apache/commons/io/input/ObservableInputStream.java

@@ -18,7 +18,6 @@
 
 import java.io.IOException;
 import java.io.InputStream;
-import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -36,51 +35,77 @@
  * @see MessageDigestCalculatingInputStream
  */
 public class ObservableInputStream extends ProxyInputStream {
+
     public static abstract class Observer {
+
         /** Called to indicate, that {@link InputStream#read()} has been invoked
          * on the {@link ObservableInputStream}, and will return a value.
          * @param pByte The value, which is being returned. This will never be -1 (EOF),
          *    because, in that case, {@link #finished()} will be invoked instead.
+         * @throws IOException if an i/o-error occurs
          */
         void data(int pByte) throws IOException {}
+ 
         /** Called to indicate, that {@link InputStream#read(byte[])}, or
          * {@link InputStream#read(byte[], int, int)} have been called, and are about to
          * invoke data.
          * @param pBuffer The byte array, which has been passed to the read call, and where
          *   data has been stored.
          * @param pOffset The offset within the byte array, where data has been stored.
          * @param pLength The number of bytes, which have been stored in the byte array.
+         * @throws IOException if an i/o-error occurs
          */
         void data(byte[] pBuffer, int pOffset, int pLength) throws IOException {}
+
         /** Called to indicate, that EOF has been seen on the underlying stream.
          * This method may be called multiple times, if the reader keeps invoking
          * either of the read methods, and they will consequently keep returning
          * EOF.
+         * @throws IOException if an i/o-error occurs
          */
         void finished() throws IOException {}
+
         /** Called to indicate, that the {@link ObservableInputStream} has been closed.
+         * @throws IOException if an i/o-error occurs
          */
         void closed() throws IOException {}
+
         /**
          * Called to indicate, that an error occurred on the underlying stream.
+         * @throws IOException if an i/o-error occurs
          */
         void error(IOException pException) throws IOException { throw pException; }
     }
 
     private final List<Observer> observers = new ArrayList<>();
-    
+
+    /**
+     * Creates a new ObservableInputStream for the given InputStream.
+     * @param pProxy the input stream to proxy
+     */
     public ObservableInputStream(InputStream pProxy) {
         super(pProxy);
     }
 
+    /**
+     * Adds an Observer.
+     * @param pObserver the observer to add
+     */
     public void add(Observer pObserver) {
         observers.add(pObserver);
     }
 
+    /**
+     * Removes an Observer.
+     * @param pObserver the observer to remove
+     */
     public void remove(Observer pObserver) {
         observers.remove(pObserver);
     }
 
+    /**
+     * Removes all Observers.
+     */
     public void removeAllObservers() {
         observers.clear();
     }
@@ -201,6 +226,9 @@ protected void noteClosed() throws IOException {
         }
     }
 
+    /** Gets all currently registered observers.
+     * @return a list of the currently registered observers
+     */
     protected List<Observer> getObservers() {
         return observers;
     }

src/main/java/org/apache/commons/io/output/WriterOutputStream.java

@@ -310,6 +310,11 @@ private void flushOutput() throws IOException {
         }
     }
 
+    /**
+     * Check if the JDK in use properly supports the given charset.
+     * 
+     * @param charset the charset to check the support for
+     */
     private static void checkIbmJdkWithBrokenUTF16(Charset charset){
         if (!"UTF-16".equals(charset.name())) {
             return;