文本与集合的读取写入方式总结

Posted 2020-09-26

//1.从文本中读取并添加到集合,按行读取

  1 public static void main(String[] args) throws IOException {
  2         BufferedReader br = new BufferedReader(new FileReader("g.txt"));
  3         ArrayList<String> arr = new ArrayList<>();
  4 
  5         String line;
  6          while ((line = br.readLine()) != null) { // 按行读取文本文件
  7             arr.add(line); // 添加至集合
  8         }
  9 
 10         for (int i = 0; i < arr.size(); i++) {
 11              System.out.println(arr.get(i));
 12          }
 13      }
 14 

//2.把集合中的数据写入到文本,每个数据一行

  1 public static void main(String[] args) throws IOException {
  2          ArrayList<String> arrStr = new ArrayList<>();
  3 
  4         arrStr.add("abc");
  5          arrStr.add("cde");
  6          arrStr.add("efg");
  7          arrStr.add("ghi");
  8 
  9         BufferedWriter bw = new BufferedWriter(new FileWriter("g.txt"));
 10 
 11         for (int i = 0; i < arrStr.size(); i++) {
 12              bw.write(arrStr.get(i));
 13              bw.newLine();    //每个数据一行
 14 
 15         }// for
 16          bw.close();
 17      }
 18 

//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

  1         BufferedReader br = new BufferedReader(new FileReader("c.txt"));
  2         BufferedWriter bw = new BufferedWriter(new FileWriter("d.txt"));
  3 
  4         int c;
  5          while ((c = br.read()) != -1) {
  6          bw.write(c);
  7          //bw.flush();
  8          }
  9 
 10          bw.close();
 11          br.close();

// 法二:复制文本文件,一次读一个数组

  1         BufferedReader br = new BufferedReader(new FileReader("d.txt"));
  2          BufferedWriter bw = new BufferedWriter(new FileWriter("e.txt"));
  3 
  4          char[] ch = new char[1024];
  5          int len = ch.length;
  6          while ((len = br.read(ch)) != -1) {
  7          bw.write(ch, 0, len);
  8          }
  9 
 10          bw.close();
 11          br.close();

// 法三:复制文本文件,按行读取,只能用Buffered

  1         BufferedReader br = new BufferedReader(new FileReader("e.txt"));
  2          BufferedWriter bw = new BufferedWriter(new FileWriter("f.txt"));
  3 
  4         String line;
  5          while ((line = br.readLine()) != null) {
  6              bw.write(line);
  7              bw.newLine();
  8          }
  9 
 10         bw.close();
 11          br.close();
 12 

//法四:复制文本文件,一次写一个字符数组

  1 public static void main(String[] args) throws IOException {
  2          // 创建输入字符流
  3         FileReader fr = new FileReader("b.txt");
  4          // 创建输出字符流
  5         FileWriter fw = new FileWriter("c.txt");
  6 
  7         // 字符数组的方式写入
  8         char[] ch = new char[1024];
  9          int len = ch.length;
 10          while ((len = fr.read(ch)) != -1) {
 11              fw.write(ch, 0, len);
 12              fw.flush();
 13          }
 14 
 15         fw.close();
 16          fr.close();
 17      }
 18 

//法五:复制文本文件,一次写一个字符

  1 public static void main(String[] args) throws IOException {
  2          // 创建字符流对象
  3         FileReader fr = new FileReader("a.txt");
  4 
  5         FileWriter fw = new FileWriter("b.txt");
  6 
  7         int c;
  8          while ((c = fr.read()) != -1) {
  9 
 10             fw.write(c);
 11          }
 12 
 13         fw.close();
 14          fr.close();
 15      }
 16