Java中的IO流

Java中的IO流

IO流体系图

通过捕捉获取来修改异常

public class MyTest {
    public static void main(String[] args) {
        FileOutputStream out=null;
        try {
          out = new FileOutputStream("a.txt");
            out.write(100);

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (out!=null){
                    out.close();
                }

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

用字节流复制单层文件

public class MyTest2 {
    public static void main(String[] args) throws IOException {
        FileInputStream in = new FileInputStream("MyTest.txt");
        FileOutputStream out = new FileOutputStream("B.txt");
        int len=0;
        byte[] bytes = new byte[1024];
        while ((len=in.read(bytes))!=-1){
            out.write(bytes,0,len);
        }
        in.close();
        out.close();
    }
}

高效字节流复制文件，通过写入字节缓冲区，在将缓冲区的数据一次性写入文件，可以提高读写效率

public class MyTest2 {
    public static void main(String[] args) throws IOException {
        BufferedInputStream in = new BufferedInputStream(new FileInputStream("E:\\领悟.mp3"));
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("领悟.mp3"));
        int len=0;
        byte[] bytes = new byte[1024 * 8];
        while ((len=in.read(bytes))!=-1){
            out.write(bytes,0,len);
            out.flush();
        }
        in.close();
        out.close();
    }
}

用字符流高效流复制文本文件

public class MyTest2 {
    public static void main(String[] args)  {
        BufferedReader in=null;
        BufferedWriter writer=null;
        try {
            in= new BufferedReader(new FileReader("MyTest.txt"));
            writer= new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\Desktop\\MyTest.java"));
            int len=0;
            char[] chars = new char[1024];
            while ((len=in.read(chars))!=-1){
                writer.write(chars,0,len);
                writer.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
                try {
                    if (in != null) {
                        in.close();
                    }
                    if (writer!=null){
                        writer.close();
                    }
                    } catch(IOException e){
                        e.printStackTrace();
                    }
                }
        }
    }

把Arrlist集合中的文件存入到文本文件中

public class MyTest2 {
    public static void main(String[] args) throws IOException {
        ArrayList<String> list = new ArrayList<>();
        BufferedWriter writer = new BufferedWriter(new FileWriter("C.txt"));
        list.add("乔布斯");
        list.add("库克");
        list.add("比尔科茨");
        list.add("乔丹");
        for (String s : list) {
                writer.write(s);
                writer.newLine();
                writer.flush();
            }
        writer.close();
    }
    }

遍历集合，取出数据，写入文本文件，writer.newline（）重新写入一行

利用集合和字符流编一个点名系统

public class MyTest2 {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("C.txt"));
        ArrayList<String> list = new ArrayList<>();
        String str=null;
        while ((str=reader.readLine())!=null){
            list.add(str);
        }
        Random random = new Random();
        int i = random.nextInt(list.size());
        System.out.println(list.get(i));
    }
    }

复制多级文件夹

public class MyTest2 {
    public static void main(String[] args) throws IOException {
        File file = new File("E:\\MyTest");
        File file1 = new File("E:\\MyTest2");
        if (!file1.exists()) {
            file1.mkdirs();
        }
        copyFolder(file, file1);
    }

    private static void copyFolder(File file, File file1) throws IOException {
        File[] files = file.listFiles();
        for (File file2 : files) {
            if (file2.isFile()) {
                copyFiles(file2, file1);
            } else {
                File file3 = new File(file1, file2.getName());
                if (!file3.exists()) {
                    file3.mkdirs();
                }
                copyFolder(file2, file3);
            }
        }
    }
    private static void copyFiles(File file2, File file1) throws IOException {
        FileInputStream in = new FileInputStream(file2);
        FileOutputStream out = new FileOutputStream(new File(file1,file2.getName()));
        int len = 0;
        byte[] bytes = new byte[1024 * 8];
        while ((len = in.read(bytes)) != -1) {
            out.write(bytes, 0, len);
            out.flush();
        }
        in.close();
        out.close();
    }
}

将多首歌合并成一首歌，

public class MyTest3 {
    public static void main(String[] args) throws IOException {
        FileInputStream in = new FileInputStream("E:\\领悟.mp3");
        FileInputStream in1 = new FileInputStream("E:\\许巍-曾经的你.mp3");
        FileOutputStream out = new FileOutputStream("E:\\大合唱.mp3");
        ArrayList<FileInputStream> list = new ArrayList<>();//创建集合，把两首歌放到一个集合中
        list.add(in);
        list.add(in1);
        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        int len=0;
        byte[] bytes1 = new byte[1024 * 8];
        for (FileInputStream fileInputStream : list) {//遍历集合，把数据放到内存操作流中
            while ((len=fileInputStream.read(bytes1))!=-1){
                bytes.write(bytes1,0,len);
            }
        }
        in.close();
        in1.close();
        byte[] bytes2 = bytes.toByteArray();//取出数据，转换成字节数组
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes2);
        int len2=0;
        byte[] bytes3 = new byte[1024 * 8];
        while ((len2=byteArrayInputStream.read(bytes3))!=-1){
            out.write(bytes3,0,len2);
        }
        out.close();
    }
}

利用Scanner和字节打印流复制文本文件

public class MyTest4 {
    public static void main(String[] args) throws FileNotFoundException {
        Scanner scanner = new Scanner(new FileInputStream("MyTest.txt"));
        PrintWriter printWriter = new PrintWriter("MyTest2.txt");
        while (scanner.hasNextLine()){
            String string = scanner.nextLine();
            printWriter.println(string);
        }
scanner.close();
        printWriter.close();
    }
}

键盘的第二种录入方式

public class MyTest4 {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        //InputStream in = System.in;
        while (true){
            System.out.println("请输入数据");
            String string = reader.readLine();
            System.out.println(string);
            if ("bye".equals(string)){
                break;
            }
        }
    }
}