content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * 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
   *
   *      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 com.alibaba.csp.sentinel.util.function;
  
  /**
   * Function functional interface from JDK 8.
   */
  public interface Function<T, R> {
  
      /**
       * Applies this function to the given argument.
       *
       * @param t the function argument
       * @return the function result
       */
      R apply(T t);
  
      /**
       * Returns a function that always returns its input argument.
       *
       * @param <T> the type of the input and output objects to the function
       * @return a function that always returns its input argument
       */
      static <T> Function<T, T> identity() {
          return t -> t;
      }
  }
  