1. P247改变标准输入输出设备

System.setIn(new FileInputStream("PersonDemo.java"));
System.setOut(new PrintStream("zz.txt"));

 2. P248：异常的日志信息

import java.io.*;
import java.util.*;
import java.text.*;

class ExceptionInfo {
    public static void main(String[] args) {
        try {
            int[] arr = new int[2];
            System.out.println(arr[3]);
        } catch (Exception e) {
            // e.printStackTrace();
            // e.printStackTrace(System.out);
            try {
                Date d = new Date();
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
                String s = sdf.format(d);
                PrintStream ps = new PrintStream("exception.log");
                // ps.write(s.getBytes());
                ps.println(s);
                System.setOut(ps);
            } catch (IOException ex) {
                throw new RuntimeException("日志文件创建失败");
            }
            e.printStackTrace(System.out);
        }
    }
}
// log4j

 3. 做了problem484、problem9。代码较简单，这里不记录了。