Java IO流练习

1、利用缓冲流，采用不同方式 ，实现图片视频的复制功能，并记录时间 比较效率。

import java.io.*;

public class BufferedCopy {

    public static void main(String[] args) throws IOException {
        String src = "d:/fine.mp4"; //复制的源文件名
        String dst = "d:/fineCopy.mp4"; //复制的目的文件名
        copyImg(src, dst);
        copyImg2(src,dst);
    }

    //单个字符复制
    public static void copyImg(String src, String dst) throws IOException {
        BufferedInputStream in = new BufferedInputStream(new FileInputStream(new File(src)));
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(new File(dst)));
        int readData;
        long start = System.currentTimeMillis();
        while ((readData = in.read()) != -1) {
            out.write(readData);
            out.flush();
        }
        long end = System.currentTimeMillis();
        System.out.println("单个字符复制视频需要" + (end - start) + "ms");
        in.close();
        out.close();
    }

    //多个字符复制
    public static void copyImg2(String src, String dst) throws IOException {
        BufferedInputStream in = new BufferedInputStream(new FileInputStream(new File(src)));
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(new File(dst)));
        int readCount;
        byte[] bytes = new byte[4096];
        long start = System.currentTimeMillis();
        while ((readCount = in.read(bytes)) != -1) {
            out.write(bytes,0,readCount);
        }
        long end = System.currentTimeMillis();
        System.out.println("按数组复制视频需要" + (end - start) + "ms");
        in.close();
        out.close();
    }

}

2、有这样的一个words数组，数组中每个字符串的格式为“词性:单词”。

String[] words = {"verb:eat","verb:drink","verb:sleep","verb:play","noun:rice","noun:meat","noun:hand","noun:hair"};

根据单词性质动词verb全部存入verb.txt文件中;

根据单词性质名词noun全部存入noun.txt文件中。

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class WordsCopy {

    public static void main(String[] args) throws IOException {
        String[] words = {"verb:eat", "verb:drink", "verb:sleep", "verb:play",
                "noun:rice", "noun:meat", "noun:hand", "noun:hair"};
        saveWords(words);
    }

    private static void saveWords(String[] words) throws IOException {
        FileOutputStream verbOut = new FileOutputStream(new File("verb.txt"), true);
        FileOutputStream nounOut = new FileOutputStream(new File("noun.txt"), true);

        for (int i = 0; i < words.length; i++) {
            char[] chs = new char[6];
            words[i].getChars(5, words[i].length(), chs, 0);
            String str = String.valueOf(chs)+"\n";
            if (words[i].contains("verb")) {
                verbOut.write(str.getBytes());
            } else if (words[i].contains("noun")) {
                nounOut.write(str.getBytes());
            }
        }
        verbOut.close();
        nounOut.close();
    }

}

3、递归查找指定目录中(包括子目录中)，所有的.java文件，并且，把所有这些找到的java文件，复制(是复制不是移动)到一个指定的目录下。
目录结构为如下：

• firstLevel目录中，包含一个secondLevel目录和a1.txt和b1.java文件；
• secondLevel目录中包含dir1和dir2两个目录，和a2.txt和b2.java文件；
• dir1目录中包含a3.txt和b3.java文件；
• dir2目录是一个空目录；

import java.io.*;
import java.util.ArrayList;
import java.util.List;


public class QueryFile {

    public static void main(String[] args) throws IOException {
        String src = "D:\\firstLevel";
        String dst = "D:\\copy\\";
        copyFile(src, dst);
    }

    /**
     * 1, 获取当前层下的所有文件及文件夹
     * 2， 判断每个元素是文件还是文件夹
     * 3， 文件则判断是否是.java文件，是就加入 List
     * 4， 文件夹则递归调用 queryFile(文件夹目录)
     *
     * @param path
     * @param javaFiles
     */
    public static void queryFile(String path, List<File> javaFiles) {
        File dir = new File(path);
        File[] files = dir.listFiles();
        if (files == null || files.length == 0) return;
        for (File file : files) {
            if (file.isFile()) {
                if (file.getName().endsWith("java")) {
                    System.out.println(file.getName());
                    javaFiles.add(file);
                }
            } else if (file.isDirectory()) {
                queryFile(file.getAbsolutePath(), javaFiles);
            }
        }
    }

    public static void copyFile(String src, String dst) throws IOException {
        List<File> javaFiles = new ArrayList<>();
        queryFile(src, javaFiles);
        System.out.println(javaFiles.size());
        byte[] bytes = new byte[2048];
        int readCount;
        for (File file : javaFiles) {
            FileOutputStream out = new FileOutputStream(dst + file.getName());
            FileInputStream in = new FileInputStream(file);
            while ((readCount = in.read(bytes)) != -1) {
                out.write(bytes, 0, readCount);
                System.out.println(readCount);
            }
            in.close();
            out.close();
        }
    }
}

4、从磁盘上读取一个文本文件（如某个java源代码），分别统计出文件中英文字母、空格、数字字符的个数。(文本文件中的数字指的是数字字符)

import java.io.*;
import java.util.Arrays;


public class CountCharacter {

    public static void main(String[] args) throws IOException {

        File file = new File("a.txt");
        int[] count = count(file);
        System.out.println("字母有 "+count[0]+" 个。");
        System.out.println("空格有 "+count[1]+" 个。");
        System.out.println("数字有 "+count[2]+" 个。");
    }

    public static int[] count(File file) throws IOException {
        int[] cnt = new int[3];
        Arrays.fill(cnt, 0);
        InputStreamReader in = new InputStreamReader(new FileInputStream(file));
        char[] chars = new char[1024];
        while (in.read(chars) != -1) {
            for (int i = 0; i < chars.length; i++) {
                if (chars[i] >= 'a' && chars[i] <= 'z' || chars[i] >= 'A' && chars[i] <= 'Z') {
                    cnt[0]++;
                } else if (chars[i] == ' ') {
                    cnt[1]++;
                } else if (chars[i] >= '0' && chars[i] <= '9') {
                    cnt[2]++;
                }
            }
        }
        in.close();
        return cnt;
    }

}

5、在一个磁盘的文件里保存26个英文小写字母（乱序），将他们读入内存中，进行排序，把排好顺序的数再重新追加写到磁盘的该文件中。

import java.io.*;
import java.util.Arrays;

public class RWAndSort {
    public static void main(String[] args) throws IOException{
        File file = new File("b.txt");
        reloadCharacter(file);
    }

    public static void reloadCharacter(File file) throws IOException {
        FileReader fileReader = new FileReader(file);
        char[] chars = new char[27];
        fileReader.read(chars);
        sortCharacter(chars);
        FileWriter fileWriter = new FileWriter(file);
        fileWriter.write(chars);
        fileWriter.close();
        fileReader.close();
    }

    public static char[] sortCharacter(char[] chars) {
         Arrays.sort(chars);
         return chars;
    }
}