diff --git a/src/main/java/xyz/zhouxy/plusone/commons/function/package-info.java b/src/main/java/xyz/zhouxy/plusone/commons/function/package-info.java
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+/*
+ * Copyright 2025 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.
+ */
+
+/**
+ * 函数式编程
+ *
+ * <h2>PredicateTools</h2>
+ * <p>
+ * {@link PredicateTools} 用于 {@link java.util.function.Predicate} 的相关操作。
+ * </p>
+ *
+ * <h2>Functional interfaces</h2>
+ * <p>
+ * 补充一些 JDK 没有，而项目中可能用得上的函数式接口：
+ * <pre>
+ * | Group         | FunctionalInterface  | method                           |
+ * | ------------- | -------------------- | -------------------------------- |
+ * | UnaryOperator | BoolUnaryOperator    | boolean applyAsBool (boolean)    |
+ * | UnaryOperator | CharUnaryOperator    | char applyAsChar(char)           |
+ * | Throwing      | Executable           | void execute() throws E          |
+ * | Throwing      | ThrowingConsumer     | void accept(T) throws E          |
+ * | Throwing      | ThrowingPredicate    | boolean test(T) throws E         |
+ * | Throwing      | ThrowingSupplier     | T get() throws E                 |
+ * | Optional      | OptionalSupplier     | Optional&lt;T&gt; get() throws E       |
+ * | Optional      | ToOptionalBiFunction | Optional&lt;R&gt; apply(T,U)           |
+ * | Optional      | ToOptionalFunction   | Optional&lt;R&gt; apply(T)             |
+ * </pre>
+ * </p>
+ */
+package xyz.zhouxy.plusone.commons.function;