Update Javadoc and constructors in the channels package

src/main/java/org/apache/commons/io/channels/ByteArraySeekableByteChannel.java

@@ -104,12 +104,14 @@ public static Builder builder() {
     /**
      * Constructs a new channel backed directly by the given byte array.
      *
-     * <p>The channel initially contains the full contents of the array, with its
-     * size set to {@code bytes.length} and its position set to {@code 0}.</p>
+     * <p>
+     * The channel initially contains the full contents of the array, with its size set to {@code bytes.length} and its position set to {@code 0}.
+     * </p>
      *
-     * <p>Reads and writes operate on the shared array.
-     * If a write operation extends beyond the current capacity, the channel will
-     * automatically allocate a larger backing array and copy the existing contents.</p>
+     * <p>
+     * Reads and writes operate on the shared array. If a write operation extends beyond the current capacity, the channel will automatically allocate a larger
+     * backing array and copy the existing contents.
+     * </p>
      *
      * @param bytes The byte array to wrap, must not be {@code null}
      * @return A new channel that uses the given array as its initial backing store.

src/main/java/org/apache/commons/io/channels/CloseShieldChannel.java

@@ -36,11 +36,13 @@
 /**
  * Creates a close-shielding proxy for a {@link Channel}.
  *
- * <p>The returned proxy implements all {@link Channel} sub-interfaces that are both supported by this implementation and actually implemented by the given
- * delegate.</p>
- *
- * <p>The following interfaces are supported:</p>
- *
+ * <p>
+ * The returned proxy implements all {@link Channel} sub-interfaces that are both supported by this implementation and actually implemented by the given
+ * delegate.
+ * </p>
+ * <p>
+ * The following interfaces are supported:
+ * </p>
  * <ul>
  * <li>{@link AsynchronousChannel}</li>
  * <li>{@link ByteChannel}</li>

src/main/java/org/apache/commons/io/channels/CloseShieldChannelHandler.java

@@ -37,6 +37,9 @@
 import java.util.Objects;
 import java.util.Set;
 
+/**
+ * An {@link InvocationHandler} supporting the implementation of {@link CloseShieldChannel}.
+ */
 final class CloseShieldChannelHandler implements InvocationHandler {
 
     private static final Set<Class<? extends Channel>> SUPPORTED_INTERFACES;
@@ -154,7 +157,7 @@ private Object invokeObjectMethod(final Object proxy, final Method method, final
             return false;
         }
         default:
-            // Not possible, all non-final Object methods are handled above
+            // Not possible, all non-final Object methods are handled above.
             return null;
         }
     }

src/main/java/org/apache/commons/io/channels/FilterByteChannel.java

@@ -31,6 +31,16 @@
 
 /**
  * A {@link ByteChannel} filter which delegates to the wrapped {@link ByteChannel}.
+ * <p>
+ * A {@code FilterByteChannel} wraps some other channel, which it uses as its basic source of data, possibly transforming the data along the way or providing
+ * additional functionality. The class {@code FilterByteChannel} itself simply overrides methods of {@code ByteChannel} with versions that pass all requests to
+ * the wrapped channel. Subclasses of {@code FilterByteChannel} may of course override any methods declared or inherited by {@code FilterByteChannel}, and may
+ * also provide additional fields and methods.
+ * </p>
+ * <p>
+ * You construct s simple instance with the {@link FilterByteChannel#FilterByteChannel(ByteChannel) channel constructor} and more advanced instances through the
+ * {@link Builder}.
+ * </p>
  *
  * @param <C> the {@link ByteChannel} type.
  * @see FilterInputStream
@@ -94,6 +104,15 @@ public static Builder forByteChannel() {
         super(builder);
     }
 
+    /**
+     * Constructs a new instance.
+     *
+     * @param byteChannel The channel to wrap.
+     */
+    public FilterByteChannel(final C byteChannel) {
+        super(byteChannel);
+    }
+
     @Override
     public int read(final ByteBuffer dst) throws IOException {
         return channel.read(dst);

src/main/java/org/apache/commons/io/channels/FilterChannel.java

@@ -31,6 +31,16 @@
 
 /**
  * A {@link Channel} filter which delegates to the wrapped {@link Channel}.
+ * <p>
+ * A {@code FilterChannel} wraps some other channel, which it uses as its basic source of data, possibly transforming the data along the way or providing
+ * additional functionality. The class {@code FilterChannel} itself simply overrides methods of {@code Channel} with versions that pass all requests to the
+ * wrapped channel. Subclasses of {@code FilterChannel} may of course override any methods declared or inherited by {@code FilterChannel}, and may also provide
+ * additional fields and methods.
+ * </p>
+ * <p>
+ * You construct s simple instance with the {@link FilterChannel#FilterChannel(Channel) channel constructor} and more advanced instances through the
+ * {@link Builder}.
+ * </p>
  *
  * @param <C> the {@link Channel} type.
  * @see FilterInputStream
@@ -103,6 +113,15 @@ public static Builder forChannel() {
         channel = (C) builder.getChannel(Channel.class);
     }
 
+    /**
+     * Constructs a new instance.
+     *
+     * @param channel The channel to wrap.
+     */
+    public FilterChannel(final C channel) {
+        this.channel = channel;
+    }
+
     @Override
     public void close() throws IOException {
         channel.close();

src/main/java/org/apache/commons/io/channels/FilterFileChannel.java

@@ -20,22 +20,89 @@
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.MappedByteBuffer;
+import java.nio.channels.Channel;
 import java.nio.channels.FileChannel;
 import java.nio.channels.FileLock;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
 import java.util.Objects;
 
+import org.apache.commons.io.build.AbstractStreamBuilder;
+
 /**
  * Filters a {@link FileChannel}.
+ * <p>
+ * A {@code FilterFileChannel} wraps some other channel, which it uses as its basic source of data, possibly transforming the data along the way or providing
+ * additional functionality. The class {@code FilterFileChannel} itself simply overrides methods of {@code FileChannel} with versions that pass all requests to
+ * the wrapped channel. Subclasses of {@code FilterFileChannel} may of course override any methods declared or inherited by {@code FilterFileChannel}, and may
+ * also provide additional fields and methods.
+ * </p>
+ * <p>
+ * You construct s simple instance with the {@link FilterFileChannel#FilterFileChannel(FileChannel) channel constructor} and more advanced instances through the
+ * {@link Builder}.
+ * </p>
  *
  * @since 2.22.0
  */
 public class FilterFileChannel extends FileChannel {
 
+    /**
+     * Builds instances of {@link FilterFileChannel} for subclasses.
+     *
+     * @param <F> The {@link FilterFileChannel} type.
+     * @param <C> The {@link Channel} type wrapped by the FilterChannel.
+     * @param <B> The builder type.
+     */
+    public abstract static class AbstractBuilder<F extends FilterFileChannel, C extends FileChannel, B extends AbstractBuilder<F, C, B>>
+            extends AbstractStreamBuilder<F, AbstractBuilder<F, C, B>> {
+
+        /**
+         * Constructs instance for subclasses.
+         */
+        protected AbstractBuilder() {
+            // empty
+        }
+    }
+
+    /**
+     * Builds instances of {@link FilterFileChannel}.
+     */
+    public static class Builder extends AbstractBuilder<FilterFileChannel, FileChannel, Builder> {
+
+        /**
+         * Builds instances of {@link FilterChannel}.
+         */
+        protected Builder() {
+            // empty
+        }
+
+        @Override
+        public FilterFileChannel get() throws IOException {
+            return new FilterFileChannel(this);
+        }
+    }
+
+    /**
+     * Creates a new {@link Builder}.
+     *
+     * @return a new {@link Builder}.
+     */
+    public static Builder forFilterFileChannel() {
+        return new Builder();
+    }
+
     final FileChannel fileChannel;
 
-    FilterFileChannel(final FileChannel fileChannel) {
+    private FilterFileChannel(final Builder builder) throws IOException {
+        this.fileChannel = builder.getChannel(FileChannel.class);
+    }
+
+    /**
+     * Constructs a new instance.
+     *
+     * @param fileChannel the file channel to wrap.
+     */
+    public FilterFileChannel(final FileChannel fileChannel) {
         this.fileChannel = Objects.requireNonNull(fileChannel, "fileChannel");
     }
 

src/main/java/org/apache/commons/io/channels/FilterReadableByteChannel.java

@@ -31,6 +31,16 @@
 
 /**
  * A {@link ReadableByteChannel} filter which delegates to the wrapped {@link ReadableByteChannel}.
+ * <p>
+ * A {@code FilterReadableByteChannel} wraps some other channel, which it uses as its basic source of data, possibly transforming the data along the way or
+ * providing additional functionality. The class {@code FilterReadableByteChannel} itself simply overrides methods of {@code ReadableByteChannel} with versions
+ * that pass all requests to the wrapped channel. Subclasses of {@code FilterReadableByteChannel} may of course override any methods declared or inherited by
+ * {@code FilterReadableByteChannel}, and may also provide additional fields and methods.
+ * </p>
+ * <p>
+ * You construct s simple instance with the {@link FilterReadableByteChannel#FilterReadableByteChannel(ReadableByteChannel) channel constructor} and more
+ * advanced instances through the {@link Builder}.
+ * </p>
  *
  * @param <C> the {@link ReadableByteChannel} type.
  * @see FilterInputStream
@@ -94,6 +104,15 @@ public static Builder forReadableByteChannel() {
         super(builder);
     }
 
+    /**
+     * Constructs a new instance.
+     *
+     * @param channel The channel to wrap.
+     */
+    public FilterReadableByteChannel(final C channel) {
+        super(channel);
+    }
+
     @Override
     public int read(final ByteBuffer dst) throws IOException {
         return channel.read(dst);

src/main/java/org/apache/commons/io/channels/FilterSeekableByteChannel.java

@@ -30,6 +30,16 @@
 
 /**
  * A {@link SeekableByteChannel} filter which delegates to the wrapped {@link SeekableByteChannel}.
+ * <p>
+ * A {@code FilterSeekableByteChannel} wraps some other channel, which it uses as its basic source of data, possibly transforming the data along the way or
+ * providing additional functionality. The class {@code FilterSeekableByteChannel} itself simply overrides methods of {@code SeekableByteChannel} with versions
+ * that pass all requests to the wrapped channel. Subclasses of {@code FilterSeekableByteChannel} may of course override any methods declared or inherited by
+ * {@code FilterSeekableByteChannel}, and may also provide additional fields and methods.
+ * </p>
+ * <p>
+ * You construct s simple instance with the {@link FilterSeekableByteChannel#FilterSeekableByteChannel(SeekableByteChannel) Channel constructor} and more
+ * advanced instances through the {@link Builder}.
+ * </p>
  *
  * @param <C> the {@link SeekableByteChannel} type.
  * @see FilterInputStream
@@ -93,6 +103,15 @@ public static Builder forSeekableByteChannel() {
         super(builder);
     }
 
+    /**
+     * Constructs a new instance.
+     *
+     * @param channel The channel to wrap.
+     */
+    public FilterSeekableByteChannel(final C channel) {
+        super(channel);
+    }
+
     @Override
     public long position() throws IOException {
         return channel.position();

src/main/java/org/apache/commons/io/channels/FilterWritableByteChannel.java

@@ -31,6 +31,16 @@
 
 /**
  * A {@link WritableByteChannel} filter which delegates to the wrapped {@link WritableByteChannel}.
+ * <p>
+ * A {@code FilterWritableByteChannel} wraps some other channel, which it uses as its basic source of data, possibly transforming the data along the way or
+ * providing additional functionality. The class {@code FilterWritableByteChannel} itself simply overrides methods of {@code WritableByteChannel} with versions
+ * that pass all requests to the wrapped channel. Subclasses of {@code FilterWritableByteChannel} may of course override any methods declared or inherited by
+ * {@code WritableByteChannel}, and may also provide additional fields and methods.
+ * </p>
+ * <p>
+ * You construct s simple instance with the {@link FilterWritableByteChannel#FilterWritableByteChannel(WritableByteChannel) Channel constructor} and more
+ * advanced instances through the {@link Builder}.
+ * </p>
  *
  * @param <C> the {@link WritableByteChannel} type.
  * @see FilterInputStream
@@ -94,6 +104,15 @@ public static Builder forWritableByteChannel() {
         super(builder);
     }
 
+    /**
+     * Constructs a new instance.
+     *
+     * @param channel The channel to wrap.
+     */
+    public FilterWritableByteChannel(final C channel) {
+        super(channel);
+    }
+
     @Override
     public int write(final ByteBuffer src) throws IOException {
         return channel.write(src);

src/test/java/org/apache/commons/io/channels/CloseShieldChannelFilterByteChannelTest.java

@@ -55,7 +55,7 @@ class CloseShieldChannelFilterByteChannelTest {
     @BeforeEach
     void setUp() throws IOException {
         mockChannel = mock(ByteChannel.class);
-        filterChannel = FilterByteChannel.forByteChannel().setChannel(mockChannel).get();
+        filterChannel = new FilterByteChannel<>(mockChannel);
         shield = CloseShieldChannel.wrap(filterChannel);
     }
 

src/test/java/org/apache/commons/io/channels/FilterFileChannelTest.java

@@ -53,9 +53,14 @@ private FileChannel mockFileChannel() {
         return mock(FileChannel.class);
     }
 
+    @Test
+    void testBuilderForNothing() throws IOException {
+        assertThrows(IllegalStateException.class, () -> FilterFileChannel.forFilterFileChannel().get());
+    }
+
     @Test
     void testConstructorRequiresNonNullChannel() {
-        assertThrows(NullPointerException.class, () -> new FilterFileChannel(null));
+        assertThrows(NullPointerException.class, () -> new FilterFileChannel((FileChannel) null));
     }
 
     @Test

src/test/java/org/apache/commons/io/channels/FilterReadableByteChannelTest.java

@@ -40,7 +40,7 @@
 class FilterReadableByteChannelTest {
 
     private FilterReadableByteChannel<ReadableByteChannel> build(final ReadableByteChannel channel) throws IOException {
-        return FilterReadableByteChannel.forReadableByteChannel().setChannel(channel).get();
+        return new FilterReadableByteChannel(channel);
     }
 
     @Test

src/test/java/org/apache/commons/io/channels/FilterSeekableByteChannelTest.java

@@ -40,7 +40,7 @@
 class FilterSeekableByteChannelTest {
 
     private FilterSeekableByteChannel<SeekableByteChannel> build(final SeekableByteChannel channel) throws IOException {
-        return FilterSeekableByteChannel.forSeekableByteChannel().setChannel(channel).get();
+        return new FilterSeekableByteChannel(channel);
     }
 
     @Test

src/test/java/org/apache/commons/io/channels/FilterWritableByteChannelTest.java

@@ -40,7 +40,7 @@
 class FilterWritableByteChannelTest {
 
     private FilterWritableByteChannel<WritableByteChannel> build(final WritableByteChannel channel) throws IOException {
-        return FilterWritableByteChannel.forWritableByteChannel().setChannel(channel).get();
+        return new FilterWritableByteChannel(channel);
     }
 
     @Test