随机选择文件，向后写入文件内容

一、 需求概述

指定文件目录，搜索某类型文本文件，随机选择几个做内容交换。

思路：

将原始数据看做内齿轮，复制的内容数据看做外齿轮，将外部齿轮顺时针挪一步后写入，便实现了数据的腾挪！

二、Java实现

1、添加依赖

pom.xml

<dependency>
	<groupId>org.slf4j</groupId>
	<artifactId>slf4j-simple</artifactId>
	<version>2.0.16</version>
</dependency>
<dependency>
	<groupId>org.apache.commons</groupId>
	<artifactId>commons-lang3</artifactId>
	<version>3.5</version>
</dependency>
<dependency>
	<groupId>commons-io</groupId>
	<artifactId>commons-io</artifactId>
	<version>2.15.0</version>
</dependency>
<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
	<version>1.18.12</version>
	<scope>provided</scope>
</dependency>
<dependency>
	<groupId>org.junit.jupiter</groupId>
	<artifactId>junit-jupiter-engine</artifactId>
	<version>5.5.2</version>
</dependency>

2、源码实现

import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Objects;
import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

import org.apache.commons.io.FileUtils;
import org.apache.commons.lang3.StringUtils;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

import lombok.extern.slf4j.Slf4j;

/**
 * 随机选择文件，向后写入文件内容
 */
@Slf4j
public class FileExchange
{
    static String path = System.getenv().get("USERPROFILE") + "\\Pictures\\";
    
    File directory = new File(path);
    
    /**
     * 创建测试文件
     */
    @BeforeAll
    public static void init()
    {
        IntStream.rangeClosed(0, 10).forEach(i -> {
            try
            {
                File file = new File(path + i + ".txt");
                FileUtils.writeStringToFile(file, Objects.toString(i), StandardCharsets.UTF_8);
            }
            catch (IOException e)
            {
                log.error(e.getMessage(), e);
            }
        });
    }
    
    @Test
    public void test()
    {
        List<File> files = FileUtils.listFiles(directory, new String[] {"txt"}, true).stream().collect(Collectors.toList());
        
        // 随机选择多个
        List<File> chooseFiles = new Random().ints(5, 0, files.size())
            .mapToObj(index -> files.get(index))
            .distinct()
            .peek(f -> log.info("{}", f.getAbsolutePath())) // 打印
            .collect(Collectors.toList());
        
        int length = chooseFiles.size();
        if (length > 1)
        {
            List<String> texts = chooseFiles.stream().map(file -> readText(file)).collect(Collectors.toList());
            if (texts.stream().allMatch(text -> StringUtils.isNotBlank(text)))
            {
                AtomicInteger index = new AtomicInteger();
                texts.forEach(text -> {
                    try
                    {
                        File dest = chooseFiles.get(index.incrementAndGet() % length);
                        FileUtils.writeStringToFile(dest, text, StandardCharsets.UTF_8);
                        log.info("{} ===> {}", text, dest.getAbsolutePath());
                    }
                    catch (IOException e)
                    {
                        log.error(e.getMessage(), e);
                    }
                });
            }
        }
    }
    
    /**
     * 读取文件文本内容
     * 
     * @param file
     * @return
     */
    private String readText(File file)
    {
        try
        {
            return FileUtils.readFileToString(file, StandardCharsets.UTF_8);
        }
        catch (IOException e)
        {
            log.error(e.getMessage(), e);
            return null;
        }
    }
}

三、运行结果

2025-03-04 18:44:56.204  INFO 27280 --- [main] c.f.f.FileExchange             : C:\Users\DELL\Pictures\6.txt
2025-03-04 18:44:56.206  INFO 27280 --- [main] c.f.f.FileExchange             : C:\Users\DELL\Pictures\3.txt
2025-03-04 18:44:56.206  INFO 27280 --- [main] c.f.f.FileExchange             : C:\Users\DELL\Pictures\8.txt
2025-03-04 18:44:56.206  INFO 27280 --- [main] c.f.f.FileExchange             : C:\Users\DELL\Pictures\9.txt
2025-03-04 18:44:56.206  INFO 27280 --- [main] c.f.f.FileExchange             : C:\Users\DELL\Pictures\5.txt
2025-03-04 18:44:56.213  INFO 27280 --- [main] c.f.f.FileExchange             : 6 ===> C:\Users\DELL\Pictures\3.txt
2025-03-04 18:44:56.214  INFO 27280 --- [main] c.f.f.FileExchange             : 3 ===> C:\Users\DELL\Pictures\8.txt
2025-03-04 18:44:56.214  INFO 27280 --- [main] c.f.f.FileExchange             : 8 ===> C:\Users\DELL\Pictures\9.txt
2025-03-04 18:44:56.215  INFO 27280 --- [main] c.f.f.FileExchange             : 9 ===> C:\Users\DELL\Pictures\5.txt
2025-03-04 18:44:56.215  INFO 27280 --- [main] c.f.f.FileExchange             : 5 ===> C:\Users\DELL\Pictures\6.txt