更改不可变 Map 的构建方式；改用静态工厂方法创建 ValueSet 对象。

src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java

@@ -17,11 +17,13 @@
 package xyz.zhouxy.plusone.commons.util;
 
 import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
 import java.util.Objects;
 
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableMap.Builder;
+
+import xyz.zhouxy.plusone.commons.annotation.StaticFactoryMethod;
+
 /**
  * 枚举类
  */
@@ -30,8 +32,9 @@ public abstract class Enumeration<T extends Enumeration<T>> implements Comparabl
     protected final String name;
 
     protected Enumeration(final int id, final String name) {
+        Assert.hasText(name, "Name of enumeration must has text.");
         this.id = id;
-        this.name = Objects.requireNonNull(name);
+        this.name = name;
     }
 
     public final int getId() {
@@ -70,16 +73,20 @@ public abstract class Enumeration<T extends Enumeration<T>> implements Comparabl
     }
 
     protected static final class ValueSet<T extends Enumeration<T>> {
-        private final Map<Integer, T> valueMap;
+        private final ImmutableMap<Integer, T> valueMap;
+
+        private ValueSet(ImmutableMap<Integer, T> valueMap) {
+            this.valueMap = valueMap;
+        }
 
         @SafeVarargs
-        public ValueSet(T... values) {
-            Map<Integer, T> temp = new HashMap<>(values.length);
+        @StaticFactoryMethod(ValueSet.class)
+        public static <T extends Enumeration<T>> ValueSet<T> of(T... values) {
+            Builder<Integer, T> builder = ImmutableMap.builder();
             for (T value : values) {
-                Assert.notNull(value, "Value must not be null.");
-                temp.put(value.getId(), value);
+                builder.put(value.getId(), value);
             }
-            this.valueMap = Collections.unmodifiableMap(temp);
+            return new ValueSet<>(builder.build());
         }
 
         public T get(int id) {