Java文件的读取与写入(追加写入)

 文件读取与写入的demo，将其封装成一个函数，直接传入需要读取的文件路径，写入只要执行文件和写入内容即可。

import java.io.*;

public class FileTest {
    public static void main(String[] args) {
        //获得当前项目的路径
        String path = System.getProperty("user.dir");

        String result = readFile(path + "/1.txt");
        System.out.println(result);
        writeFile(path + "/2.txt", "写入1\n2\n3\n");
    }

    /**
     * 读取文件
     */
    public static String readFile(String pathname) {
        StringBuffer str = new StringBuffer();
        //防止文件建立或读取失败，用catch捕捉错误并打印
        try (FileReader reader = new FileReader(pathname);
             BufferedReader br = new BufferedReader(reader)
        ) {
            String line;//逐行读取
            while ((line = br.readLine()) != null) {
                str.append(line);
                str.append("\r\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return str.toString();
    }

    /**
     * 写入文件，如果文件存在，追加写入
     */
    public static void writeFile(String pathname, String content) {
        try {
            File writeName = new File(pathname);
            try (FileWriter writer = new FileWriter(writeName, true);
                 BufferedWriter out = new BufferedWriter(writer)
            ) {
                out.write(content);
                out.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}