[Java IO]整理

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1. 基本

1.1 概述

1. Java的IO操作中有面向字节(Byte)和面向字符(Character)两种方式。
   

   • 面向字节的操作为以8位为单位对二进制的数据进行操作，对数据不进行转换，这些类都是InputStream和OutputStream的子类。面向字符的操作为以字符为单位对数据进行操作，在读的时候将二进制数据转为字符，在写的时候将字符转为二进制数据，这些类都是Reader和Writer的子类。

2. IO常用类的继承关系图如下：
   

使用系统路径标识来组建路径

@Test// 使用系统路径标识来组建路径public void testFileAttr() throws IOException {    System.out.println(File.separator);    System.out.println(File.pathSeparator);    // 这样组成的路径能实现在windows和linux中的通用性    String fileName = "D:" + File.separator + "hello_testFileAttr.txt";    File f = new File(fileName);    f.createNewFile();}

取得本地的默认编码

@Test// 取得本地的默认编码public void testGetLocalEncoding() {    System.out.println("系统默认编码为：" + System.getProperty("file.encoding"));}

创建文件夹

@Test// File.mkdir() 创建文件夹public void testCreateMkdir() {    String fileName = "D:" + File.separator + "hello";    File f = new File(fileName);    f.mkdir();}

创建文件

@Test// 创建文件public void testCreateFile() {    File f = new File("D:\\hello_testCreateFile.txt");// 参数为待创建[文件路径+文件名]组成的字符串    try {        f.createNewFile();    } catch (Exception e) {        e.printStackTrace();    }}

判断文件是否存在、删除文件

@Test// File.exists()、File.delete() 判断文件是否存在、删除文件public void testDelFile() {    String fileName = "D:" + File.separator + "hello_testFileAttr.txt";    File f = new File(fileName);    if (f.exists()) {        f.delete();        System.out.println("文件已经删除");    } else {        System.out.println("文件不存在");    }}

列出全部文件

@Test// File.list() 列出指定目录的全部文件（包括隐藏文件）// File.listFiles() 列出指定目录下全部带完整路径的文件（包括隐藏文件）public void testListAllFile() {    String fileName = "D:" + File.separator;    File f = new File(fileName);    String[] str = f.list();// 返回的是Sring数组    for (int i = 0; i < str.length; i++) {        System.out.println(str[i]);    }    System.out.println("--------------");    File[] files = f.listFiles();// 返回的是File[]    for (int i = 0; i < files.length; i++) {        System.out.println(files[i]);    }}

判断一个指定的路径是否为目录

@Test// 使用isDirectory判断一个指定的路径是否为目录，如果目录不存在也是返回NOpublic void testIsDirectory() {    String fileName = "D:" + File.separator + "hello";    File f = new File(fileName);    if (f.isDirectory()) {        System.out.println("YES");    } else {        System.out.println("NO");    }}

打印出所有文件的路径

// 打印出所有文件的路径public void print(File f) {    if (f != null) {        if (f.isDirectory()) {// 如果f是目录            File[] fileArray = f.listFiles();// 得到目录下的所有文件            if (fileArray != null) {                for (int i = 0; i < fileArray.length; i++) {                    print(fileArray[i]);// 递归调用                }            }        } else {// 如果f是文件，直接输出文件路径            System.out.println(f);        }    }}

列出指定目录的全部内容

@Testpublic void testListAll() {    String fileName = "D:" + File.separator;    File f = new File(fileName);    print(f);}

2. 读取写入流、转换流

字节流，向文件中写入字符串，会覆盖原来的内容！

@Test// 字节流，向文件中写入字符串，会覆盖原来的内容！【FileOutputStream->write()】public void testWriteString() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    OutputStream out = new FileOutputStream(f);// ★参数文件    String str = "你好";    byte[] b = str.getBytes();    out.write(b);    out.close();}

一个字节一个字节的写入字符串，会覆盖原来的内容！

@Test// 第二种方式：一个字节一个字节的写入字符串，会覆盖原来的内容！public void testWriteStringOneByOne() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    OutputStream out = new FileOutputStream(f);    String str = "妹子，我喜欢你！";    byte[] b = str.getBytes();    for (int i = 0; i < b.length; i++) {        out.write(b[i]);    }    out.close();}

字节流:向文件中追加新内容：

@Test// 字节流:向文件中追加新内容：public void testAppendString() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    OutputStream out = new FileOutputStream(f, true);    String str = "亲爱的，嫁给我吧！";// 可以用\r\n换行，如：String str="\r\n你好";    byte[] b = str.getBytes();    for (int i = 0; i < b.length; i++) {        out.write(b[i]);    }    out.close();}

使用RandomAccessFile写入文

@Test// 使用RandomAccessFile写入文件，打开文件后会发现那是乱码。public void testRandomAccessFile() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    RandomAccessFile demo = new RandomAccessFile(f, "rw");// 设置文件读写权限    demo.writeBytes("Hewei I love you!");    demo.writeInt(12);    demo.writeBoolean(true);    demo.writeChar('A');    demo.writeFloat(1.21f);    demo.writeDouble(12.123);    demo.close();}

字节流：读文件内容

@Test// ★字节流：读文件内容【FileInputStream->read()】public void testReadFileString() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    InputStream in = new FileInputStream(f);    byte[] b = new byte[1024];    in.read(b);    in.close();    System.out.println(new String(b));}

字节流：读文件内容

@Test// ★字节流：读文件内容，一个个的读以节省空间public void testReadFileStringOneByOne() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    InputStream in = new FileInputStream(f);    byte[] b = new byte[(int) f.length()];    for (int i = 0; i < b.length; i++) {        b[i] = (byte) in.read();    }    in.close();    System.out.println(new String(b));}

不知道文件有多大读取文件内容

@Test// 在知道文件的内容多大，然后才展开的，有时候我们不知道文件有多大，这种情况下用下面这种方法public void testReadFileStringBySureEnd() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    InputStream in = new FileInputStream(f);    byte[] b = new byte[1024];    int count = 0, temp = 0;    while ((temp = in.read()) != (-1)) {// ★当独到文件末尾的时候会返回-1，用此判断是否独到文件的末尾。        b[count++] = (byte) temp;    }    in.close();    System.out.println(new String(b));}

字符流：向文件中写入数据

@Test//★★字符流：向文件中写入数据【FileWriter->write】public void testWriteFileStringByCharStream() throws Exception {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    Writer out = new FileWriter(f);    String str = "妹子，我又来了";// 把以前的内容覆盖了    out.write(str);    out.close();}

字符流:从文件中读出内容

@Test// ★★字符流:从文件中读出内容public void testReadFileStringByCharStream() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    Reader read = new FileReader(f);    read.close();}

循环读取文件内容

@Test// ★采用循环读取的方式，因为我们有时候不知道文件到底有多大public void testReadFileStringBySureEndInCharStream() throws IOException {    String fileName = "D:" + File.separator + "hello.txt";    File f = new File(fileName);    char[] ch = new char[100];    Reader read = new FileReader(f);    int temp = 0;    int count = 0;    while ((temp = read.read()) != (-1)) {        ch[count++] = (char) temp;    }    read.close();    System.out.println(new String(ch, 0, count));}

文件内容拷贝

@Test// ★★★将hello.txt中的内容拷贝被到world.txt中（覆盖原来有的内容），如果world.txt中不存在，则创建该文件，public void testCopyFile() throws IOException {    String file1 = "D:" + File.separator + "hello.txt";    String file2 = "D:" + File.separator + "world.txt";    InputStream input = new FileInputStream(file1);    OutputStream output = new FileOutputStream(file2);    if ((input != null) && (output != null)) {        int temp = 0;        while ((temp = input.read()) != (-1)) {            output.write(temp);        }    }    input.close();    output.close();}

流转换：字节输出流转化为字符输出流

@Test// ★★将字节输出流转化为字符输出流public void testByteOutStream2CharOutStream() throws Exception {    String fileName = "d:" + File.separator + "hello.txt";    File file = new File(fileName);    Writer out = new OutputStreamWriter(new FileOutputStream(file));    out.write("hello");    out.close();}

流转换：字节输入流变为字符输入流

@Test// ★★将字节输入流变为字符输入流public void testByteInStream2CharInStream() throws Exception {    String fileName = "d:" + File.separator + "hello.txt";    File file = new File(fileName);    Reader read = new InputStreamReader(new FileInputStream(file));    char[] b = new char[100];    int len = read.read(b);    System.out.println(new String(b, 0, len));    read.close();}

[内存操作流内]ByteArrayInputStream

@Test// ★★[内存操作流内]ByteArrayInputStream：内存操作流内一般使用来生成一些临时信息，这样可以避免删除的麻烦public void testByteArrayInputStream() throws IOException {    String str = "ILOVEYOU";    ByteArrayInputStream input = new ByteArrayInputStream(str.getBytes());    ByteArrayOutputStream output = new ByteArrayOutputStream();    int temp = 0;    while ((temp = input.read()) != -1) {        char ch = (char) temp;        output.write(Character.toLowerCase(ch));    }    String outStr = output.toString();    input.close();    output.close();    System.out.println(outStr);}

PipedOutputStream 管道输出流

@Test// PipedOutputStream 管道输出流；PipedInputStream 管道输入流public void testPipeStreamSend() {    Send_PipedStreamTest send = new Send_PipedStreamTest();    Recive_PipedStreamTest recive = new Recive_PipedStreamTest();    try {// 管道连接        send.getOut().connect(recive.getInput());    } catch (Exception e) {        e.printStackTrace();    }    new Thread(send).start();    new Thread(recive).start();}

打印流PrintStream进行输出

@Test// 使用PrintStream进行输出public void testPrintStreamOut() throws Exception {    PrintStream print = new PrintStream(new FileOutputStream(new File("d:"            + File.separator + "hello.txt")));    print.println(true);// 输入到hello.txt文件中    print.println("Rollen");    print.close();}

PrintStream进行格式化输出

@Test// 使用PrintStream进行输出，并进行格式化public void testFormatPrintOut() throws Exception {    PrintStream print = new PrintStream(new FileOutputStream(new File("d:"            + File.separator + "hello.txt")));    String name = "Rollen";    int age = 20;    print.printf("姓名：%s. 年龄：%d.", name, age);    print.close();}

字符流的缓冲区：BufferedReader

@Test// BufferedReader:只能接受字符流的缓冲区，为每一个中文需要占据两个字节，所以需要将System.in这个字节输入流变为字符输入流// 采用：BufferedReader buf = new BufferedReader(new// InputStreamReader(System.in));// 使用缓冲区从键盘上读入内容public void testBufferedReader() {    BufferedReader buf = new BufferedReader(            new InputStreamReader(System.in));    String str = null;    System.out.println("请输入内容:");    try {        str = buf.readLine();    } catch (IOException e) {        e.printStackTrace();    }    System.out.println("你输入的内容是：" + str);}

Scanner类：可以接受任何的输入流

@Test// ★★Scanner类：从键盘读数据，可以接受任何的输入流。使用Scanner类从文件中读出内容public void testScanner() {    File file = new File("d:" + File.separator + "hello.txt");    Scanner sca = null;    try {        sca = new Scanner(file);    } catch (FileNotFoundException e) {        e.printStackTrace();    }    String str = sca.next();    System.out.println("从文件中读取的内容是：" + str);}

数据操作流DataOutputStream、DataInputStream类

@Testpublic void testData() throws Exception {    File file = new File("d:" + File.separator + "hello.txt");    char[] ch = { 'A', 'B', 'C' };    DataOutputStream out = null;    out = new DataOutputStream(new FileOutputStream(file));    for (char temp : ch) {        out.writeChar(temp);    }    out.close();}

3. 流合并、文件压缩与解压

合并流 SequenceInputStream

@Test// 合并流 SequenceInputStream:将2个流合并在一起，比如将两个txt中的内容合并为另外一个txt// 下面结果会在hello.txt文件中包含hello1.txt和hello2.txt文件中的内容。public void testSequenceInputStream() throws Exception {    File file1 = new File("d:" + File.separator + "hello1.txt");    File file2 = new File("d:" + File.separator + "hello2.txt");    File file3 = new File("d:" + File.separator + "hello.txt");    InputStream input1 = new FileInputStream(file1);// 如果文件不存在，报系统找不到指定的文件    InputStream input2 = new FileInputStream(file2);    OutputStream output = new FileOutputStream(file3);    // 合并流    SequenceInputStream sis = new SequenceInputStream(input1, input2);    int temp = 0;    while ((temp = sis.read()) != -1) {        output.write(temp);    }    input1.close();    input2.close();    output.close();    sis.close();}

文件压缩 ZipOutputStream

@Testpublic void testZipStream() throws Exception {    File file = new File("d:" + File.separator + "hello.txt");    File zipFile = new File("d:" + File.separator + "hello.zip");    InputStream input = new FileInputStream(file);    ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(            zipFile));    zipOut.putNextEntry(new ZipEntry(file.getName()));    // 设置注释    zipOut.setComment("hello");    int temp = 0;    while ((temp = input.read()) != -1) {        zipOut.write(temp);    }    input.close();    zipOut.close();}

压缩多个文件

@Testpublic void testZipMutilFile() throws Exception {    // 要被压缩的文件夹    File file = new File("d:" + File.separator + "temp");    File zipFile = new File("d:" + File.separator + "zipFile.zip");// 压缩后的文件名    InputStream input = null;    ZipOutputStream zipOut = new ZipOutputStream(new FileOutputStream(            zipFile));    zipOut.setComment("hello");    if (file.isDirectory()) {// 压缩temp问文件夹下的所有文件        File[] files = file.listFiles();        for (int i = 0; i < files.length; ++i) {            input = new FileInputStream(files[i]);            zipOut.putNextEntry(new ZipEntry(file.getName()                    + File.separator + files[i].getName()));            int temp = 0;            while ((temp = input.read()) != -1) {                zipOut.write(temp);            }            input.close();        }    }    zipOut.close();}

ZipFile类getName()

@Testpublic void testUnderStandZipFile() throws Exception {    File file = new File("d:" + File.separator + "zipFile.zip");    ZipFile zipFile = new ZipFile(file);    System.out.println("压缩文件的名称为：" + zipFile.getName());}

解压缩文件：ZipEntry（压缩文件中只有一个文件的情况）

@Testpublic void testZipFile() throws Exception {    File file = new File("d:" + File.separator + "hello.zip");    File outFile = new File("d:" + File.separator + "unZipFile.txt");    ZipFile zipFile = new ZipFile(file);    ZipEntry entry = zipFile.getEntry("hello.txt");    InputStream input = zipFile.getInputStream(entry);    OutputStream output = new FileOutputStream(outFile);    int temp = 0;    while ((temp = input.read()) != -1) {        output.write(temp);    }    input.close();    output.close();}

解压缩多个文件

@Test// 解压缩多个文件的时候，ZipEntry就无法使用了，如果想操作更加复杂的压缩文件，我们就必须使用ZipInputStream类public void testUnZipMutilFile() throws Exception {    File file = new File("d:" + File.separator + "zipFile.zip");    File outFile = null;    ZipFile zipFile = new ZipFile(file);    ZipInputStream zipInput = new ZipInputStream(new FileInputStream(file));    ZipEntry entry = null;    InputStream input = null;    OutputStream output = null;    while ((entry = zipInput.getNextEntry()) != null) {        System.out.println("解压缩" + entry.getName() + "文件");        outFile = new File("d:" + File.separator + entry.getName());        if (!outFile.getParentFile().exists()) {            outFile.getParentFile().mkdir();        }        if (!outFile.exists()) {            outFile.createNewFile();        }        input = zipFile.getInputStream(entry);        output = new FileOutputStream(outFile);        int temp = 0;        while ((temp = input.read()) != -1) {            output.write(temp);        }        input.close();        output.close();    }}

4. 其它

PushBackInputStream回退流

@Testpublic void testPushBackInputStream() throws IOException {    String str = "hello,rollenholt";    PushbackInputStream push = null;    ByteArrayInputStream bat = null;    bat = new ByteArrayInputStream(str.getBytes());    push = new PushbackInputStream(bat);    int temp = 0;    while ((temp = push.read()) != -1) {        if (temp == ',') {            push.unread(temp);            temp = push.read();            System.out.print("(回退" + (char) temp + ") ");        } else {            System.out.print((char) temp);        }    }}

ObjectInputStream

@Test// 示范：查看hello.txt二进制文件里面的内容public void testObjectInputStream() throws Exception {    File file = new File("d:" + File.separator + "hello.txt");    ObjectInputStream input = new ObjectInputStream(new FileInputStream(file));    Object obj = input.readObject();    input.close();    System.out.println(obj);}

序列化

@Test//被Serializable接口声明的类的对象的属性都将被序列化，但是如果想自定义序列化的内容的时候，就需要实现Externalizable接口public void test() throws Exception {    File file = new File("d:" + File.separator + "hello.txt");    ObjectInputStream input = new ObjectInputStream(new FileInputStream(file));    Object obj = input.readObject();    input.close();    System.out.println(obj);}