diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/Assert.java b/src/main/java/xyz/zhouxy/plusone/commons/util/Assert.java
index ee35e8c..3bc0191 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/Assert.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/Assert.java
@@ -166,7 +166,7 @@ public class Assert {
         Assert.isFalse((arr == null || arr.length() == 0), errorMessageTemplate, args);
     }
 
-    // private consrtuctor
+    // private constructor
     private Assert() {
         throw new IllegalStateException("Utility class");
     }
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java b/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java
index bca9392..8c255a2 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java
@@ -74,12 +74,12 @@ public abstract class Enumeration<T extends Enumeration<T>> implements Comparabl
 
         @SafeVarargs
         public ValueSet(T... values) {
-            Map<Integer, T> valueMap = new HashMap<>(values.length);
+            Map<Integer, T> temp = new HashMap<>(values.length);
             for (T value : values) {
                 Assert.notNull(value, "Value must not be null.");
-                valueMap.put(value.getId(), value);
+                temp.put(value.getId(), value);
             }
-            this.valueMap = Collections.unmodifiableMap(valueMap);
+            this.valueMap = Collections.unmodifiableMap(temp);
         }
 
         public T get(int id) {
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/RegexUtil.java b/src/main/java/xyz/zhouxy/plusone/commons/util/RegexUtil.java
index 66446fd..5af00c3 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/RegexUtil.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/RegexUtil.java
@@ -16,7 +16,6 @@
 
 package xyz.zhouxy.plusone.commons.util;
 
-import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 import java.util.Map;
@@ -26,7 +25,7 @@ import java.util.regex.Pattern;
 
 public class RegexUtil {
 
-    private static final Map<String, @Nonnull Pattern> PATTERN_CACHE = new ConcurrentHashMap<>();
+    private static final Map<String, Pattern> PATTERN_CACHE = new ConcurrentHashMap<>();
 
     public static Pattern getPattern(final String regex) {
         Objects.requireNonNull(regex);
@@ -34,9 +33,6 @@ public class RegexUtil {
             return PATTERN_CACHE.get(regex);
         }
         Pattern pattern = Pattern.compile(regex);
-        if (pattern == null) {
-            throw new IllegalArgumentException("Regex must not be null.");
-        }
         PATTERN_CACHE.put(regex, pattern);
         return pattern;
     }
@@ -47,14 +43,12 @@ public class RegexUtil {
 
     public static boolean matches(@Nullable CharSequence input, Pattern pattern) {
         Assert.notNull(pattern, "Pattern must not be null.");
-        return pattern.matcher(input).matches();
+        return input != null && pattern.matcher(input).matches();
     }
 
     public static boolean matchesOr(@Nullable CharSequence input, String... regexes) {
-        boolean isMatched;
         for (String regex : regexes) {
-            isMatched = matches(input, regex);
-            if (isMatched) {
+            if (matches(input, regex)) {
                 return true;
             }
         }
@@ -62,10 +56,8 @@ public class RegexUtil {
     }
 
     public static boolean matchesOr(@Nullable CharSequence input, Pattern... patterns) {
-        boolean isMatched;
         for (Pattern pattern : patterns) {
-            isMatched = matches(input, pattern);
-            if (isMatched) {
+            if (matches(input, pattern)) {
                 return true;
             }
         }
@@ -73,10 +65,8 @@ public class RegexUtil {
     }
 
     public static boolean matchesAnd(@Nullable CharSequence input, String... regexes) {
-        boolean isMatched;
         for (String regex : regexes) {
-            isMatched = matches(input, regex);
-            if (!isMatched) {
+            if (!matches(input, regex)) {
                 return false;
             }
         }
@@ -84,10 +74,8 @@ public class RegexUtil {
     }
 
     public static boolean matchesAnd(@Nullable CharSequence input, Pattern... patterns) {
-        boolean isMatched;
         for (Pattern pattern : patterns) {
-            isMatched = matches(input, pattern);
-            if (!isMatched) {
+            if (!matches(input, pattern)) {
                 return false;
             }
         }