java IO 基本操作实例

1，复制文件到另一个文件

File file = new File("d://tt.txt");
        if(!file.exists()){
            file.createNewFile();
        }
        BufferedReader read = null;
        BufferedWriter writer = null;
        File fileCopy = new File("d://00//tt00.txt");
        if(!fileCopy.exists()){
            fileCopy.getParentFile().mkdirs();
            fileCopy.createNewFile();
        }
        writer = new BufferedWriter(new FileWriter(fileCopy));
        read = new BufferedReader(new FileReader(file));
        String tempString = null;
        while ((tempString = read.readLine()) != null) {
            writer.append(tempString);
            writer.newLine();
            writer.flush();
        }
        read.close();
        writer.close();
        System.out.println("copy over");

2，字节读取

File file = new File(fileName);
        InputStream in = null;
        try {
            System.out.println("以字节为单位读取文件内容，一次读一个字节：");
            // 一次读一个字节
            in = new FileInputStream(file);
            int tempbyte;
            while ((tempbyte = in.read()) != -1) {
                System.out.print(tempbyte);
            }
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }

3，字符读取 有一下三种方法读取：

 3.1

File file = new File(fileName);
        Reader reader = null;
        try {
            System.out.println("以字节为单位读取文件内容，一次读一个字节：");
            // 一次读一个字节
            reader = new InputStreamReader(new FileInputStream(file));
            int tempbyte;
            while ((tempbyte = reader.read()) != -1) {
                System.out.print((char) tempbyte);
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
    }

3.2 字符 数组读取

FileReader fr = new FileReader("d:/test.txt"); 
char[] c = new  char[1024];
 int len = 0; 
while((len = fr.read(c)) != -1){
  System.out.println(new String(c,0,len)); 
}
 fr.close();

3.3 字符  整行读取 

 FileReader fr = new FileReader("d:/test.txt"); 
BufferedReader bfr = new BufferedReader(fr);
 File fwFile = new File("d://writer.txt");
 if(!fwFile.exists()){ fwFile.createNewFile(); } 
FileWriter fw = new FileWriter(fwFile);
 BufferedWriter bfw = new BufferedWriter(fw);
 String line = null; while((line = bfr.readLine()) != null){
  System.out.println(line); 
  bfw.write(line); 
  bfw.newLine();
  bfw.flush(); }
 fr.close(); 
 bfw.close();