package com.study.chap3;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

/**
 * 环绕执行场景：
 *      读取文件一行数据，演示一个传统的流程，如何改造成支持lambda的流程
 * @author liangzj5
 * @version 1.0
 * @date 2021/11/2 13:51
 */
public class ExecuteAround {
    private static String filePath = ExecuteAround.class.getClassLoader().getResource("data.txt").getPath();

    // 传统实现：固定写死逻辑
    public static String processFile() throws IOException {
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))){
            return br.readLine();
        }
    }
    //基于Lambda扩展
    //1、行为参数化：
    //1.1 引入函数式接口
    @FunctionalInterface
    interface ProcessFilePredicate{
        String process(BufferedReader br) throws IOException ;
    }
    //1.2 用函数式接口传统行为
    public static String processFile(ProcessFilePredicate p) throws IOException {
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))){
            return p.process(br);
        }
    }

    public static void main(String[] args) throws IOException {
        System.out.println(processFile());
        System.out.println("---");
        // 基于Lambda的灵活使用
        String oneLine = processFile((BufferedReader br) -> br.readLine());
        System.out.println(oneLine);
        System.out.println("---");
        int a=22;
        String twoLine = processFile((BufferedReader br) -> a+br.readLine()+br.readLine());
        System.out.println(a);
        System.out.println(twoLine);
    }
}