diff --git a/src/main/java/org/apache/commons/codec/binary/BinaryCodec.java b/src/main/java/org/apache/commons/codec/binary/BinaryCodec.java
index 590dd3e..c7f383e 100644
--- a/src/main/java/org/apache/commons/codec/binary/BinaryCodec.java
+++ b/src/main/java/org/apache/commons/codec/binary/BinaryCodec.java
@@ -80,13 +80,14 @@
         if (isEmpty(ascii)) {
             return EMPTY_BYTE_ARRAY;
         }
+        final int asciiLength = ascii.length;
         // get length/8 times bytes with 3 bit shifts to the right of the length
-        final byte[] l_raw = new byte[ascii.length >> 3];
+        final byte[] l_raw = new byte[asciiLength >> 3];
         /*
          * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
          * loop.
          */
-        for (int ii = 0, jj = ascii.length - 1; ii < l_raw.length; ii++, jj -= 8) {
+        for (int ii = 0, jj = asciiLength - 1; ii < l_raw.length; ii++, jj -= 8) {
             for (int bits = 0; bits < BITS.length; ++bits) {
                 if (ascii[jj - bits] == '1') {
                     l_raw[ii] |= BITS[bits];
@@ -112,13 +113,14 @@
         if (ascii == null || ascii.length == 0) {
             return EMPTY_BYTE_ARRAY;
         }
+        final int asciiLength = ascii.length;
         // get length/8 times bytes with 3 bit shifts to the right of the length
-        final byte[] l_raw = new byte[ascii.length >> 3];
+        final byte[] l_raw = new byte[asciiLength >> 3];
         /*
          * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
          * loop.
          */
-        for (int ii = 0, jj = ascii.length - 1; ii < l_raw.length; ii++, jj -= 8) {
+        for (int ii = 0, jj = asciiLength - 1; ii < l_raw.length; ii++, jj -= 8) {
             for (int bits = 0; bits < BITS.length; ++bits) {
                 if (ascii[jj - bits] == '1') {
                     l_raw[ii] |= BITS[bits];
@@ -152,13 +154,14 @@
         if (isEmpty(raw)) {
             return EMPTY_BYTE_ARRAY;
         }
+        final int rawLength = raw.length;
         // get 8 times the bytes with 3 bit shifts to the left of the length
-        final byte[] l_ascii = new byte[raw.length << 3];
+        final byte[] l_ascii = new byte[rawLength << 3];
         /*
          * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
          * loop.
          */
-        for (int ii = 0, jj = l_ascii.length - 1; ii < raw.length; ii++, jj -= 8) {
+        for (int ii = 0, jj = l_ascii.length - 1; ii < rawLength; ii++, jj -= 8) {
             for (int bits = 0; bits < BITS.length; ++bits) {
                 if ((raw[ii] & BITS[bits]) == 0) {
                     l_ascii[jj - bits] = '0';
@@ -182,13 +185,14 @@
         if (isEmpty(raw)) {
             return EMPTY_CHAR_ARRAY;
         }
+        final int rawLength = raw.length;
         // get 8 times the bytes with 3 bit shifts to the left of the length
-        final char[] l_ascii = new char[raw.length << 3];
+        final char[] l_ascii = new char[rawLength << 3];
         /*
          * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
          * loop.
          */
-        for (int ii = 0, jj = l_ascii.length - 1; ii < raw.length; ii++, jj -= 8) {
+        for (int ii = 0, jj = l_ascii.length - 1; ii < rawLength; ii++, jj -= 8) {
             for (int bits = 0; bits < BITS.length; ++bits) {
                 if ((raw[ii] & BITS[bits]) == 0) {
                     l_ascii[jj - bits] = '0';
diff --git a/src/main/java/org/apache/commons/codec/binary/Hex.java b/src/main/java/org/apache/commons/codec/binary/Hex.java
index 2294956..7075ab9 100644
--- a/src/main/java/org/apache/commons/codec/binary/Hex.java
+++ b/src/main/java/org/apache/commons/codec/binary/Hex.java
@@ -166,9 +166,9 @@
      * @since 1.4
      */
     protected static char[] encodeHex(final byte[] data, final char[] toDigits) {
-        final int l = data.length;
-        final char[] out = new char[l << 1];
-        encodeHex(data, 0, data.length, toDigits, out, 0);
+        final int dataLength = data.length;
+        final char[] out = new char[dataLength << 1];
+        encodeHex(data, 0, dataLength, toDigits, out, 0);
         return out;
     }
 
@@ -519,7 +519,7 @@
      */
     @Override
     public Object encode(final Object object) throws EncoderException {
-        byte[] byteArray;
+        final byte[] byteArray;
         if (object instanceof String) {
             byteArray = ((String) object).getBytes(this.getCharset());
         } else if (object instanceof ByteBuffer) {
diff --git a/src/main/java/org/apache/commons/codec/cli/Digest.java b/src/main/java/org/apache/commons/codec/cli/Digest.java
index 4e553cf..9815034 100644
--- a/src/main/java/org/apache/commons/codec/cli/Digest.java
+++ b/src/main/java/org/apache/commons/codec/cli/Digest.java
@@ -61,16 +61,17 @@
         if (args == null) {
             throw new IllegalArgumentException("args");
         }
-        if (args.length == 0) {
+        final int argsLength = args.length;
+        if (argsLength == 0) {
             throw new IllegalArgumentException(
                     String.format("Usage: java %s [algorithm] [FILE|DIRECTORY|string] ...", Digest.class.getName()));
         }
         this.args = args;
         algorithm = args[0];
-        if (args.length <= 1) {
+        if (argsLength <= 1) {
             inputs = null;
         } else {
-            inputs = new String[args.length -1];
+            inputs = new String[argsLength - 1];
             System.arraycopy(args, 1, inputs, 0, inputs.length);
         }
     }
diff --git a/src/main/java/org/apache/commons/codec/digest/Md5Crypt.java b/src/main/java/org/apache/commons/codec/digest/Md5Crypt.java
index f607b88..82011a2 100644
--- a/src/main/java/org/apache/commons/codec/digest/Md5Crypt.java
+++ b/src/main/java/org/apache/commons/codec/digest/Md5Crypt.java
@@ -283,7 +283,7 @@
         final int keyLen = keyBytes.length;
 
         // Extract the real salt from the given string which can be a complete hash string.
-        String saltString;
+        final String saltString;
         if (salt == null) {
             saltString = B64.getRandomSalt(8, random);
         } else {
diff --git a/src/main/java/org/apache/commons/codec/digest/MurmurHash3.java b/src/main/java/org/apache/commons/codec/digest/MurmurHash3.java
index 6b471df..0c28cff 100644
--- a/src/main/java/org/apache/commons/codec/digest/MurmurHash3.java
+++ b/src/main/java/org/apache/commons/codec/digest/MurmurHash3.java
@@ -1078,8 +1078,8 @@
             }
 
             // Combine unprocessed bytes with new bytes.
-            int newOffset;
-            int newLength;
+            final int newOffset;
+            final int newLength;
             if (unprocessedLength > 0) {
                 int k = -1;
                 switch (unprocessedLength) {
diff --git a/src/main/java/org/apache/commons/codec/digest/UnixCrypt.java b/src/main/java/org/apache/commons/codec/digest/UnixCrypt.java
index 7be4958..b77e4f3 100644
--- a/src/main/java/org/apache/commons/codec/digest/UnixCrypt.java
+++ b/src/main/java/org/apache/commons/codec/digest/UnixCrypt.java
@@ -220,7 +220,8 @@
         final byte key[] = new byte[8];
         Arrays.fill(key, (byte) 0);
 
-        for (int i = 0; i < key.length && i < original.length; i++) {
+        final int originalLength = original.length;
+        for (int i = 0; i < key.length && i < originalLength; i++) {
             final int iChar = original[i];
             key[i] = (byte) (iChar << 1);
         }
diff --git a/src/main/java/org/apache/commons/codec/language/Metaphone.java b/src/main/java/org/apache/commons/codec/language/Metaphone.java
index 84a8575..5ee6466 100644
--- a/src/main/java/org/apache/commons/codec/language/Metaphone.java
+++ b/src/main/java/org/apache/commons/codec/language/Metaphone.java
@@ -89,7 +89,7 @@
      */
     public String metaphone(final String txt) {
         boolean hard = false;
-        int txtLength;
+        final int txtLength;
         if (txt == null || (txtLength = txt.length()) == 0) {
             return "";
         }
diff --git a/src/main/java/org/apache/commons/codec/language/bm/Rule.java b/src/main/java/org/apache/commons/codec/language/bm/Rule.java
index 644614a..d55ce8c 100644
--- a/src/main/java/org/apache/commons/codec/language/bm/Rule.java
+++ b/src/main/java/org/apache/commons/codec/language/bm/Rule.java
@@ -84,8 +84,10 @@
         public static final Comparator<Phoneme> COMPARATOR = new Comparator<Phoneme>() {
             @Override
             public int compare(final Phoneme o1, final Phoneme o2) {
-                for (int i = 0; i < o1.phonemeText.length(); i++) {
-                    if (i >= o2.phonemeText.length()) {
+                final int o1Length = o1.phonemeText.length();
+                final int o2Length = o2.phonemeText.length();
+                for (int i = 0; i < o1Length; i++) {
+                    if (i >= o2Length) {
                         return +1;
                     }
                     final int c = o1.phonemeText.charAt(i) - o2.phonemeText.charAt(i);
@@ -94,7 +96,7 @@
                     }
                 }
 
-                if (o1.phonemeText.length() < o2.phonemeText.length()) {
+                if (o1Length < o2Length) {
                     return -1;
                 }
 
@@ -205,6 +207,9 @@
 
     private static final String HASH_INCLUDE = "#include";
 
+    private static final int HASH_INCLUDE_LENGTH = HASH_INCLUDE.length();
+
+
     private static final Map<NameType, Map<RuleType, Map<String, Map<String, List<Rule>>>>> RULES =
             new EnumMap<>(NameType.class);
 
@@ -262,10 +267,13 @@
     }
 
     private static boolean endsWith(final CharSequence input, final CharSequence suffix) {
-        if (suffix.length() > input.length()) {
+        final int suffixLength = suffix.length();
+        final int inputLength = input.length();
+
+        if (suffixLength > inputLength) {
             return false;
         }
-        for (int i = input.length() - 1, j = suffix.length() - 1; j >= 0; i--, j--) {
+        for (int i = inputLength - 1, j = suffixLength - 1; j >= 0; i--, j--) {
             if (input.charAt(i) != suffix.charAt(j)) {
                 return false;
             }
@@ -419,7 +427,7 @@
 
                     if (line.startsWith(HASH_INCLUDE)) {
                         // include statement
-                        final String incl = line.substring(HASH_INCLUDE.length()).trim();
+                        final String incl = line.substring(HASH_INCLUDE_LENGTH).trim();
                         if (incl.contains(" ")) {
                             throw new IllegalArgumentException("Malformed import statement '" + rawLine + "' in " +
                                                                location);
@@ -492,7 +500,7 @@
         if (!boxes) {
             if (startsWith && endsWith) {
                 // exact match
-                if (content.length() == 0) {
+                if (content.isEmpty()) {
                     // empty
                     return new RPattern() {
                         @Override
@@ -507,7 +515,7 @@
                         return input.equals(content);
                     }
                 };
-            } else if ((startsWith || endsWith) && content.length() == 0) {
+            } else if ((startsWith || endsWith) && content.isEmpty()) {
                 // matches every string
                 return ALL_STRINGS_RMATCHER;
             } else if (startsWith) {
diff --git a/src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java b/src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java
index e18b298..5641dc8 100644
--- a/src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java
+++ b/src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java
@@ -282,12 +282,13 @@
             printable = PRINTABLE_CHARS;
         }
         final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        final int bytesLength = bytes.length;
 
         if (strict) {
             int pos = 1;
             // encode up to buffer.length - 3, the last three octets will be treated
             // separately for simplification of note #3
-            for (int i = 0; i < bytes.length - 3; i++) {
+            for (int i = 0; i < bytesLength - 3; i++) {
                 final int b = getUnsignedOctet(i, bytes);
                 if (pos < SAFE_LENGTH) {
                     // up to this length it is safe to add any byte, encoded or not
@@ -306,7 +307,7 @@
 
             // rule #3: whitespace at the end of a line *must* be encoded
             // if we would do a soft break line after this octet, encode whitespace
-            int b = getUnsignedOctet(bytes.length - 3, bytes);
+            int b = getUnsignedOctet(bytesLength - 3, bytes);
             boolean encode = !printable.get(b) || (isWhitespace(b) && pos > SAFE_LENGTH - 5);
             pos += encodeByte(b, encode, buffer);
 
@@ -318,10 +319,10 @@
                 buffer.write(CR);
                 buffer.write(LF);
             }
-            for (int i = bytes.length - 2; i < bytes.length; i++) {
+            for (int i = bytesLength - 2; i < bytesLength; i++) {
                 b = getUnsignedOctet(i, bytes);
                 // rule #3: trailing whitespace shall be encoded
-                encode = !printable.get(b) || (i > bytes.length - 2 && isWhitespace(b));
+                encode = !printable.get(b) || (i > bytesLength - 2 && isWhitespace(b));
                 encodeByte(b, encode, buffer);
             }
         } else {
diff --git a/src/main/java/org/apache/commons/codec/net/RFC1522Codec.java b/src/main/java/org/apache/commons/codec/net/RFC1522Codec.java
index 90564fe..16bbcf4 100644
--- a/src/main/java/org/apache/commons/codec/net/RFC1522Codec.java
+++ b/src/main/java/org/apache/commons/codec/net/RFC1522Codec.java
@@ -55,7 +55,7 @@
      * Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.
      * <p>
      * This method constructs the "encoded-word" header common to all the RFC 1522 codecs and then invokes
-     * {@link #doEncoding(byte [])} method of a concrete class to perform the specific encoding.
+     * {@link #doEncoding(byte[])}  method of a concrete class to perform the specific encoding.
      *
      * @param text
      *            a string to encode
@@ -85,7 +85,7 @@
      * Applies an RFC 1522 compliant encoding scheme to the given string of text with the given charset.
      * <p>
      * This method constructs the "encoded-word" header common to all the RFC 1522 codecs and then invokes
-     * {@link #doEncoding(byte [])} method of a concrete class to perform the specific encoding.
+     * {@link #doEncoding(byte[])}  method of a concrete class to perform the specific encoding.
      *
      * @param text
      *            a string to encode
@@ -111,7 +111,7 @@
      * Applies an RFC 1522 compliant decoding scheme to the given string of text.
      * <p>
      * This method processes the "encoded-word" header common to all the RFC 1522 codecs and then invokes
-     * {@link #doEncoding(byte [])} method of a concrete class to perform the specific decoding.
+     * {@link #doDecoding(byte[])}  method of a concrete class to perform the specific decoding.
      *
      * @param text
      *            a string to decode
diff --git a/src/test/java/org/apache/commons/codec/binary/Base16Test.java b/src/test/java/org/apache/commons/codec/binary/Base16Test.java
index f60709d..baae38f 100644
--- a/src/test/java/org/apache/commons/codec/binary/Base16Test.java
+++ b/src/test/java/org/apache/commons/codec/binary/Base16Test.java
@@ -85,7 +85,7 @@
 
     private void testBase16InBuffer(final int startPasSize, final int endPadSize) {
         final String content = "Hello World";
-        String encodedContent;
+        final String encodedContent;
         final byte[] bytesUtf8 = StringUtils.getBytesUtf8(content);
         byte[] buffer = ArrayUtils.addAll(bytesUtf8, new byte[endPadSize]);
         buffer = ArrayUtils.addAll(new byte[startPasSize], buffer);
diff --git a/src/test/java/org/apache/commons/codec/binary/Base32Test.java b/src/test/java/org/apache/commons/codec/binary/Base32Test.java
index 068f5f8..475bb2f 100644
--- a/src/test/java/org/apache/commons/codec/binary/Base32Test.java
+++ b/src/test/java/org/apache/commons/codec/binary/Base32Test.java
@@ -27,7 +27,6 @@
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
-import junit.framework.Assert;
 import org.apache.commons.codec.CodecPolicy;
 import org.apache.commons.codec.DecoderException;
 import org.apache.commons.lang3.ArrayUtils;
@@ -206,7 +205,7 @@
     public void testBase32BinarySamples() throws Exception {
         final Base32 codec = new Base32();
         for (final Object[] element : BASE32_BINARY_TEST_CASES) {
-            String expected;
+            final String expected;
             if(element.length > 2) {
                 expected = (String)element[2];
             } else {
diff --git a/src/test/java/org/apache/commons/codec/binary/Base64Test.java b/src/test/java/org/apache/commons/codec/binary/Base64Test.java
index a6e834b..e4be6d0 100644
--- a/src/test/java/org/apache/commons/codec/binary/Base64Test.java
+++ b/src/test/java/org/apache/commons/codec/binary/Base64Test.java
@@ -151,7 +151,7 @@
 
     private void testBase64InBuffer(final int startPasSize, final int endPadSize) {
         final String content = "Hello World";
-        String encodedContent;
+        final String encodedContent;
         final byte[] bytesUtf8 = StringUtils.getBytesUtf8(content);
         byte[] buffer = ArrayUtils.addAll(bytesUtf8, new byte[endPadSize]);
         buffer = ArrayUtils.addAll(new byte[startPasSize], buffer);
diff --git a/src/test/java/org/apache/commons/codec/binary/HexTest.java b/src/test/java/org/apache/commons/codec/binary/HexTest.java
index 7f0fc1c..bab8754 100644
--- a/src/test/java/org/apache/commons/codec/binary/HexTest.java
+++ b/src/test/java/org/apache/commons/codec/binary/HexTest.java
@@ -29,7 +29,6 @@
 import java.nio.charset.StandardCharsets;
 import java.nio.charset.UnsupportedCharsetException;
 import java.util.Arrays;
-import java.util.Random;
 import java.util.concurrent.ThreadLocalRandom;
 import org.apache.commons.codec.DecoderException;
 import org.apache.commons.codec.EncoderException;
diff --git a/src/test/java/org/apache/commons/codec/cli/DigestTest.java b/src/test/java/org/apache/commons/codec/cli/DigestTest.java
new file mode 100644
index 0000000..e5d279b
--- /dev/null
+++ b/src/test/java/org/apache/commons/codec/cli/DigestTest.java
@@ -0,0 +1,50 @@
+/*
+ * 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.codec.cli;
+
+import org.junit.Test;
+
+import java.io.IOException;
+
+
+/**
+ * Tests {@link Digest}.
+ *
+ * @since 1.17
+ */
+public class DigestTest {
+
+    /**
+     * Tests if empty arguments are handled correctly.
+     *
+     * @throws IllegalArgumentException for some failure scenarios.
+     */
+    @Test(expected = IllegalArgumentException.class)
+    public void testEmptyArguments() throws IOException {
+        Digest.main(new String[0]);
+    }
+    /**
+     * Tests if null arguments are handled correctly.
+     *
+     * @throws IllegalArgumentException for some failure scenarios.
+     */
+    @Test(expected = IllegalArgumentException.class)
+    public void testNullArguments() throws IOException {
+        Digest.main(null);
+    }
+}
diff --git a/src/test/java/org/apache/commons/codec/language/bm/PhoneticEngineRegressionTest.java b/src/test/java/org/apache/commons/codec/language/bm/PhoneticEngineRegressionTest.java
index f04fe4d..cb1a7ed 100644
--- a/src/test/java/org/apache/commons/codec/language/bm/PhoneticEngineRegressionTest.java
+++ b/src/test/java/org/apache/commons/codec/language/bm/PhoneticEngineRegressionTest.java
@@ -205,8 +205,8 @@
      * regressions in Commons-Codec.
      */
     private static String encode(final Map<String, String> args, final boolean concat, final String input) {
-        Languages.LanguageSet languageSet;
-        PhoneticEngine engine;
+        final Languages.LanguageSet languageSet;
+        final PhoneticEngine engine;
 
         // PhoneticEngine = NameType + RuleType + concat
         // we use common-codec's defaults: GENERIC + APPROX + true