Java IO

示例：字符流-将用户在控制台中输入的内容保存到文件中

public static void main(String[] args) throws IOException {//psvm
    Scanner scanner = new Scanner(System.in);
    String data = scanner.next();
    FileWriter writer = new FileWriter("f.txt");//ctrl+alt+v
    writer.write(data);
    writer.flush();
    writer.close();
}

示例：将随机生成的字符串保存到文件中

public static void main(String[] args) throws IOException {//psvm
        File file = new File("F:\\f.txt");
        FileWriter writer = new FileWriter(file);//ctrl+alt+v
        BufferedWriter bw = new BufferedWriter(writer);
        for(int i =0;i<1000000000;i++) {
            String s = UUID.randomUUID().toString();
//            System.out.println(s);
            bw.write(s);
        }
        bw.flush();
        bw.close();
    }

示例：读取文件

• 实现一

  public static void main(String[] args) throws IOException {//psvm
  File file = new File("F:\\安装GCC.txt");
  FileReader reader = new FileReader(file);
  
  int read = reader.read();   //read() 一次读取一个字符
  System.out.print((char)read);
  
  while(read != -1){
    read = reader.read();
      System.out.print((char)read);
  }
  reader.close();
  }

• 实现二

  public static void main(String[] args) throws IOException {//psvm
  File file = new File("F:\\安装GCC.txt");
  FileReader reader = new FileReader(file);
  
  char[] buf = new char[64];
  int len = reader.read(buf); //将数据读取到buf中，返回读取到的字符的个数
  while(len != -1){
      System.out.println(new String(buf,0,len));
      len = reader.read(buf);//
  }
  reader.close();
  }

• 实现三（重点）

  public static void main(String[] args) throws IOException {//psvm
  File file = new File("F:\\安装GCC.txt");
  FileReader reader = new FileReader(file);
  char[] buf = new char[64];
  int len = -1;
  while((len = reader.read(buf)) != -1){
      System.out.println(new String(buf,0,len));
  }
  reader.close();
  }

  • 实现四（重点掌握）

public static void main(String[] args) throws IOException {
    File file = new File("F:\\安装GCC.txt");
    FileReader reader = new FileReader(file);
    BufferedReader br = new BufferedReader(reader);
    String line = null;
    while((line = br.readLine()) != null){
        System.out.println(line);
    }
    br.close();
}

示例:文件复制

字符流-txt文件拷贝

实现一：

public static void main(String[] args) throws IOException {//psvm
    File file1 = new File("F:\\sources.txt");
    File file2 = new File("F:\\aim.txt");

    FileReader reader = new FileReader(file1);
    FileWriter writer = new FileWriter(file2);

    int len =-1;
    char[] buf = new char[128];

    while ((len = reader.read(buf)) != -1){
        writer.write(new String(buf,0,len));
    }

    writer.flush(); // 强制将缓存中的数据输出到目标文件中
    writer.close();
    reader.close();
}

实现二：

public static void main(String[] args) throws IOException {//psvm
    File file1 = new File("F:\\sources.txt");
    File file2 = new File("F:\\aim.txt");

    FileReader reader = new FileReader(file1);
    BufferedReader br = new BufferedReader(reader);
    FileWriter writer = new FileWriter(file2);
    BufferedWriter bw = new BufferedWriter(writer);

    int len =-1;
    char[] buf = new char[128];

    while ((len = br.read(buf)) != -1){
        bw.write(new String(buf,0,len));
    }

    bw.flush(); // 强制将缓存中的数据输出到目标文件中
    bw.close(); // 会自动删除bw所装饰的writer对象 
    br.close(); // 会自动删除所装饰的reader对象 
}

字符流-音频文件拷贝

实现一：复制音频文件

public static void main(String[] args) throws IOException {//psvm
    File sources = new File("F:\\微购 实体类 数据库工具类 编写.wmv");
    File aim = new File("F:\\微购 实体类 数据库工具类 编写2.wmv");

    FileInputStream fis = new FileInputStream(sources);
    FileOutputStream fos = new FileOutputStream(aim);
    byte[] buf = new byte[256];
    int len =-1;
    while ((len = fis.read(buf)) != -1){
        fos.write(buf,0,len);
    }
    fos.flush();
    fos.close();
    fis.close();
}

实现二：

public static void main(String[] args) throws IOException {//psvm
    File sources = new File("F:\\微购 实体类 数据库工具类 编写.wmv");
    File aim = new File("F:\\微购 实体类 数据库工具类 编写2.wmv");

    FileInputStream fis = new FileInputStream(sources);
    BufferedInputStream bis = new BufferedInputStream(fis);
    FileOutputStream fos = new FileOutputStream(aim);
    BufferedOutputStream bos = new BufferedOutputStream(fos);

    byte[] buf = new byte[256];
    int len =-1;
    while ((len = bis.read(buf)) != -1){
        bos.write(buf,0,len);
    }
    bos.flush();
    bos.close();
    bis.close();
}