io回顾

package test;

import java.io.*;

/**
 * 读取一个文件，并打印在控制台上。
 */
class FileReaderTest {
    public static void main(String[] args) throws IOException {
        FileReader fr = new FileReader("d:ss.txt");
        char[] buf = new char[1024];
        int num;
        while ((num = fr.read(buf)) != -1) {
            System.out.println(new String(buf));
            System.out.print(new String(buf, 0, num));
        }
        fr.close();
    }
}

class FileReaderDemo2 {
    public static void main(String[] args) throws IOException {
        //注意下面读的文件内部只写入"abcf"内容来测试边界问题。
        FileReader fr = new FileReader("d:ss.txt");
        //定义一个字符数组。用于存储读到字符。
        //该read(char[])返回的是读到字符个数。
        char[] buf = new char[1];
        int num1 = fr.read(buf);
        System.out.println("num1=" + num1 + "  " + new String(buf));

        int num2 = fr.read(buf);
        System.out.println("num2=" + num2 + "  " + new String(buf, 0, num2));

        int num3 = fr.read(buf);
        System.out.println("num3=" + num3 + "  " + new String(buf, 0, num3));

        fr.close();
    }
}

class FileReaderDemo3 {
    public static void main(String[] args) throws IOException {
        File f1 = new File("d:ss.txt");
        InputStreamReader read = new InputStreamReader(new FileInputStream(f1), "UTF-8");
        BufferedReader reader = new BufferedReader(read);
        String line;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
    }
}

class FileReaderDemo4 {
    public static void main(String[] args) throws IOException {
        File f1 = new File("d:ss.txt");
        InputStreamReader read = new InputStreamReader(new FileInputStream(f1), "UTF-8");
        int num;
        char[] chars = new char[1024];
        while ((num = read.read(chars)) != -1) {
            System.out.println(chars);
            System.out.println(new String(chars, 0, num));
        }
    }
}