（1）分别使用FileWriter 和 BufferedWriter 往文件exp5_1.txt和文件exp5_2.txt中写入1万个随机整数（数与数之间用空格隔开），并在控制台上显示程序运行的时间。（exp5_1.java）（2）请使用字节流的方式读出文件exp5_1.txt中内容，然后将文件中的所有奇数写入文件ex5_3.txt中，使用字符流的方式读出文件exp5_2.txt中内容，然后将文件中的所有偶数写入文件exp5_4.txt中。（exp4_2.java） （3）请使用File类的相关方法，遍历（1）、（2）两题所读写的文件所在的目录下的所有文件。（exp5_3.java）

（1）exp5_1.java

import java.io.*;
import java.util.Random;

public class exp5_1 {
    public static void main(String[] args) {
        long start = System.currentTimeMillis();
        try {
            FileWriter fw = new FileWriter("exp5_1.txt");
            BufferedWriter bw = new BufferedWriter(fw);
            Random random = new Random();
            for (int i = 0; i < 10000; i++) {
                int num = random.nextInt();
                bw.write(num + " ");
            }
            bw.close();
            fw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        long end = System.currentTimeMillis();
        System.out.println("程序运行时间：" + (end - start) + "ms");

        start = System.currentTimeMillis();
        try {
            FileOutputStream fos = new FileOutputStream("exp5_2.txt");
            OutputStreamWriter osw = new OutputStreamWriter(fos);
            BufferedWriter bw = new BufferedWriter(osw);
            Random random = new Random();
            for (int i = 0; i < 10000; i++) {
                int num = random.nextInt();
                bw.write(num + " ");
            }
            bw.close();
            osw.close();
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        end = System.currentTimeMillis();
        System.out.println("程序运行时间：" + (end - start) + "ms");
    }
}

（2）exp5_2.java

import java.io.*;

public class exp5_2 {
    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("exp5_1.txt");
            FileOutputStream fos = new FileOutputStream("exp5_3.txt");
            int num;
            while ((num = fis.read()) != -1) {
                if (num % 2 != 0) {
                    fos.write(num);
                    fos.write(' ');
                }
            }
            fis.close();
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            FileReader fr = new FileReader("exp5_2.txt");
            BufferedReader br = new BufferedReader(fr);
            FileWriter fw = new FileWriter("exp5_4.txt");
            BufferedWriter bw = new BufferedWriter(fw);
            String line;
            while ((line = br.readLine()) != null) {
                String[] nums = line.split(" ");
                for (String num : nums) {
                    int n = Integer.parseInt(num);
                    if (n % 2 == 0) {
                        bw.write(num + " ");
                    }
                }
            }
            br.close();
            fr.close();
            bw.close();
            fw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

（3）exp5_3.java

import java.io.File;

public class exp5_3 {
    public static void main(String[] args) {
        File file = new File(".");
        File[] files = file.listFiles();
        for (File f : files) {
            System.out.println(f.getName());
        }
    }
}