Add CharsetDecoders.

Author: garydgregory

src/changes/changes.xml

@@ -302,6 +302,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add CharsetEncoders.
       </action>
+     <action dev="ggregory" type="add" due-to="Gary Gregory">
+        Add CharsetDecoders.
+      </action>
       <!-- UPDATE -->
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Update FileEntry to use FileTime instead of long for file time stamps.

src/main/java/org/apache/commons/io/charset/CharsetDecoders.java

@@ -0,0 +1,40 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.io.charset;
+
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+
+/**
+ * Works with {@link CharsetDecoder}.
+ *
+ * @since 2.12.0
+ */
+public class CharsetDecoders {
+
+    /**
+     * Returns the given non-null CharsetDecoder or a new default CharsetDecoder.
+     *
+     * @param charsetDecoder The CharsetDecoder to test.
+     * @return the given non-null CharsetDecoder or a new default CharsetDecoder.
+     */
+    public static CharsetDecoder toCharsetDecoder(CharsetDecoder charsetDecoder) {
+        return charsetDecoder != null ? charsetDecoder : Charset.defaultCharset().newDecoder();
+    }
+
+}

src/main/java/org/apache/commons/io/charset/CharsetEncoders.java

@@ -20,14 +20,18 @@
 import java.nio.charset.Charset;
 import java.nio.charset.CharsetEncoder;
 
+/**
+ * Works with {@link CharsetEncoder}.
+ *
+ * @since 2.12.0
+ */
 public class CharsetEncoders {
 
     /**
      * Returns the given non-null CharsetEncoder or a new default CharsetEncoder.
      *
      * @param charsetEncoder The CharsetEncoder to test.
      * @return the given non-null CharsetEncoder or a new default CharsetEncoder.
-     * @since 2.12.0
      */
     public static CharsetEncoder toCharsetEncoder(CharsetEncoder charsetEncoder) {
         return charsetEncoder != null ? charsetEncoder : Charset.defaultCharset().newEncoder();

src/test/java/org/apache/commons/io/charset/CharsetDecdersTest.java

@@ -0,0 +1,54 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.io.charset;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.StandardCharsets;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests {@link CharsetDecoders}.
+ */
+public class CharsetDecdersTest {
+
+    @Test
+    public void testToCharsetDecoders_default() {
+        final CharsetDecoder charsetEncoder = CharsetDecoders.toCharsetDecoder(Charset.defaultCharset().newDecoder());
+        assertNotNull(charsetEncoder);
+        assertEquals(Charset.defaultCharset(), charsetEncoder.charset());
+    }
+
+    @Test
+    public void testToCharsetDecoders_ISO_8859_1() {
+        final CharsetDecoder charsetEncoder = CharsetDecoders.toCharsetDecoder(StandardCharsets.ISO_8859_1.newDecoder());
+        assertNotNull(charsetEncoder);
+        assertEquals(StandardCharsets.ISO_8859_1, charsetEncoder.charset());
+    }
+
+    @Test
+    public void testToCharsetDecoders_null() {
+        final CharsetDecoder charsetEncoder = CharsetDecoders.toCharsetDecoder(null);
+        assertNotNull(charsetEncoder);
+        assertEquals(Charset.defaultCharset(), charsetEncoder.charset());
+    }
+}