Function.java

/*
 * Copyright 2015 Google Inc. All Rights Reserved.
 *
 * 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.google.android.agera;

import android.support.annotation.NonNull;

/**
 * Determines an output value based on an input value.
 *
 * <p>The {@link Functions} class provides common functions and related utilities.
 *
 * Agera 中抽象出来的 方法 接口
 * 用于将 一个输入值 转换成 另一个值
 * 可以是不同类型之间的转换: A->B
 * 也可以是相同类型之间的转换：A->A
 * 默认三个类型为：Object, Object
 * 和 断定（ Merger ）接口的区别在于：Function 是 一对一 的关系，Merger 是 二次一 的关系
 */
public interface Function<TFrom, TTo> {

    /**
     * Returns the result of applying this function to {@code input}.
     * 转换方法
     */
    @NonNull TTo apply(@NonNull TFrom input);
}