文本与集合的读取写入方式总结

//1.从文本中读取并添加到集合,按行读取

public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new FileReader("g.txt"));
        ArrayList<String> arr = new ArrayList<>();

        String line;
         while ((line = br.readLine()) != null) { // 按行读取文本文件
            arr.add(line); // 添加至集合
        }

        for (int i = 0; i < arr.size(); i++) {
             System.out.println(arr.get(i));
         }
     }

//2.把集合中的数据写入到文本,每个数据一行

public static void main(String[] args) throws IOException {
         ArrayList<String> arrStr = new ArrayList<>();

        arrStr.add("abc");
         arrStr.add("cde");
         arrStr.add("efg");
         arrStr.add("ghi");

        BufferedWriter bw = new BufferedWriter(new FileWriter("g.txt"));

        for (int i = 0; i < arrStr.size(); i++) {
             bw.write(arrStr.get(i));
             bw.newLine();    //每个数据一行

        }// for
         bw.close();
     }

//3.复制文本文件
// 法一:复制文本文件,使用缓冲字符流,一次读一个字符

        BufferedReader br = new BufferedReader(new FileReader("c.txt"));
        BufferedWriter bw = new BufferedWriter(new FileWriter("d.txt"));

        int c;
         while ((c = br.read()) != -1) {
         bw.write(c);
         //bw.flush();
         }

         bw.close();
         br.close();

// 法二:复制文本文件,一次读一个数组

        BufferedReader br = new BufferedReader(new FileReader("d.txt"));
         BufferedWriter bw = new BufferedWriter(new FileWriter("e.txt"));

         char[] ch = new char[1024];
         int len = ch.length;
         while ((len = br.read(ch)) != -1) {
         bw.write(ch, 0, len);
         }

         bw.close();
         br.close();

// 法三:复制文本文件,按行读取,只能用Buffered

        BufferedReader br = new BufferedReader(new FileReader("e.txt"));
         BufferedWriter bw = new BufferedWriter(new FileWriter("f.txt"));

        String line;
         while ((line = br.readLine()) != null) {
             bw.write(line);
             bw.newLine();
         }

        bw.close();
         br.close();

//法四:复制文本文件,一次写一个字符数组

public static void main(String[] args) throws IOException {
         // 创建输入字符流
        FileReader fr = new FileReader("b.txt");
         // 创建输出字符流
        FileWriter fw = new FileWriter("c.txt");

        // 字符数组的方式写入
        char[] ch = new char[1024];
         int len = ch.length;
         while ((len = fr.read(ch)) != -1) {
             fw.write(ch, 0, len);
             fw.flush();
         }

        fw.close();
         fr.close();
     }

//法五:复制文本文件,一次写一个字符

public static void main(String[] args) throws IOException {
         // 创建字符流对象
        FileReader fr = new FileReader("a.txt");

        FileWriter fw = new FileWriter("b.txt");

        int c;
         while ((c = fr.read()) != -1) {

            fw.write(c);
         }

        fw.close();
         fr.close();
     }