java IO增强

File类

public class FileDemo {    public static void main(String[] args) throws Exception {        //创建以test开头temp结尾的临时文件        File temp = File.createTempFile("test", "temp", new File("F:/DB/test/"));        Thread.sleep(1000);        //退出时即删除临时文件        temp.deleteOnExit();    }}

/** * list()方法和listFiles()方法的区别 * @author L J */public class FileDemo2 {    public static void main(String[] args) {        File src = new File("F:/DB/test");        //取出所有子目录和子文件的名称        String[] subNames = src.list();        for(String temp : subNames) {            System.out.println(temp);        }        //取出所有子目录和子文件的File对象        File[] subFiles = src.listFiles();        for(File temp : subFiles) {            System.out.println(temp.getAbsolutePath());        }        //命令设计模式        subFiles = src.listFiles(new FilenameFilter() {            //dir表示src，name表示文件名            @Override            public boolean accept(File dir, String name) {                return new File(dir, name).isFile() && name.endsWith(".txt");            }        });        for(File temp : subFiles) {            System.out.println(temp.getAbsolutePath());        }        //列出所有的根路径        File[] roots = File.listRoots();        System.out.println(Arrays.toString(roots));//[C:\, E:\, F:\, G:\, H:\]    }}

FileInputStream & FileOutputStream

//读取文件public class FileInputStreamTest {    public static void main(String[] args) {        File src = new File("F:/DB/abc.txt");        InputStream is = null;        try {            is = new FileInputStream(src);            //字节数组            byte[] buf = new byte[1024];            int len = 0;            //读取            while(-1 != (len = is.read(buf))) {                String info = new String(buf, 0, len);                System.out.println(info);            }        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally{            //关闭流            if(is != null) {                try {                    is.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}

//写文件public class FileOutputStreamTest {    public static void main(String[] args) {        File dest = new File("F:/DB/abc.txt");        OutputStream os = null;        try {            //true表示追加,false表示覆盖            os = new FileOutputStream(dest, true);            String str = "bjsxt is very good\r\n";            //获取字节数组            byte[] data = str.getBytes();            os.write(data, 0, data.length);            os.flush(); //强制刷新出去        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally{            //关闭流            if(os != null) {                try {                    os.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}

文件拷贝和目录拷贝

/** * 文件工具类 * 1、拷贝文件 * 2、拷贝文件夹 * @author L J */public class FileUtils {    /**     * 拷贝文件     *      * @param src     *            文件源路径     * @param dest     *            文件目标路径     * @throws IOException     */    public static void copyFile(String src, String dest) throws IOException {        copyFile(new File(src), new File(dest));    }    /**     * 拷贝文件     *      * @param src     *            文件源路径的File对象     * @param dest     *            文件目标路径的File对象     * @throws IOException     */    public static void copyFile(File src, File dest) throws IOException {        if(! src.isFile()) {//是目录或为null            throw new IOException("只能拷贝文件");        }        //dest为已经存在的目录，不能建立与目录名字相同的文件        if(dest.isDirectory()) {            throw new IOException(dest.getAbsolutePath() + "不能建立与文件夹名字相同的文件");        }        FileInputStream fis = null;        FileOutputStream fos = null;        // 输入输出流        fis = new FileInputStream(src);        fos = new FileOutputStream(dest);        byte[] buf = new byte[1024];        int len = 0;        // 拷贝文件        while (-1 != (len = fis.read(buf))) {            fos.write(buf, 0, len);        }        fos.flush(); //强制刷出        //关闭流        fos.close();        fis.close();    }    /**     * 拷贝文件夹     * @param srcPath 源路径     * @param destPath 目标路径     */    public static void copyDir(String srcPath, String destPath) {        File src = new File(srcPath);        File dest = new File(destPath);        copyDir(src, dest);    }    /**     * 拷贝文件夹     * @param src 源目录File对象     * @param dest 目标目录File对象     */    public static void copyDir(File src, File dest) {        if(src.isDirectory()) {//文件夹            dest = new File(dest, src.getName());        }        copyDirDetai(src, dest);    }    /**     * 拷贝文件夹细节     * @param src 源目录File对象     * @param dest 目标目录File对象     */    public static void copyDirDetai(File src, File dest) {        if(src.isFile()) {  //文件            try {                FileUtils.copyFile(src, dest);            } catch (IOException e) {                e.printStackTrace();            }        }else if(src.isDirectory()) {//文件夹            //确保目标文件夹存在,有就不创建，没有就创建            dest.mkdirs();            //获取下一级目录|文件            for(File sub : src.listFiles()) {                //递归                copyDirDetai(sub, new File(dest, sub.getName()));            }        }    }    public static void main(String[] args) throws IOException {        // 源文件        String src = "F:/DB/abc.txt";        // 拷贝后的文件        String dest = "F:/DB/test/abc.txt";        copyFile(src, dest);    }}

/** * 文件夹的拷贝 * 1、如果是文件，拷贝 * 2、如果是文件夹，创建 * @author L J */public class CopyDir {    public static void main(String[] args) {        //源目录        String srcPath = "F:/DB/test";        //目标目录        String destPath = "F:/DB/dest";        //File src = new File(srcPath);        //File dest = new File(destPath);        FileUtils.copyDir(srcPath, destPath);    }}

InputStreamReader & OutputStreamWriter

将字节流转换为字符流，主要用来解决乱码问题

• 编码： 字符–编码字符集–>二进制
• 解码：二进制–解码字符集–>字符

造成乱码的一般原因：

• 编码与解码的字符集不统一
• 字节缺少，长度丢失

/** * 乱码成因分析 * @author L J */public class ConverDemo {    public static void main(String[] args) throws UnsupportedEncodingException {        //test1();        test2();    }    /**     * 字节数不完整，乱码     */    public static void test2() {        String str = "程序员";        byte[] data = str.getBytes();        //字节数不完整        System.out.println(new String(data, 0, 3));    }    /**     * 编码与解码字符集必须统一，否则乱码     * @throws UnsupportedEncodingException     */    public static void test1() throws UnsupportedEncodingException {        //解码byte-->char        String str = "程序员"; //GBK        //编码char-->byte        byte[] data = str.getBytes();        //编码与解码字符集统一        System.out.println(new String(data));  //程序员        //设定编码字符集        data = str.getBytes("UTF-8");        //编码与解码字符集不统一，乱码        System.out.println(new String(data));  //绋嬪簭鍛?        //编码        byte[] data2 = "程序员".getBytes("UTF-8");        //解码        str = new String(data2, "UTF-8");        System.out.println(str);    }}

字节数组流和文件流的对接

/** * 文件复制 * 1、文件--程序-->字节数组  * 2、字节数组--程序-->文件 * @author L J */public class ByteArrayDemo {    public static void main(String[] args) throws IOException {        byte[] data = getBytesFromFile("F:/DB/abc.txt");        toFileFromByteArray(data, "F:/DB/def.txt");    }    /**     * 字节数组--程序-->文件     * @param src 源字节数组     * @throws IOException      */    public static void toFileFromByteArray(byte[] src, String destPath) throws IOException {        //目的地        File dest = new File(destPath);        //字节数组输入流        InputStream is = new BufferedInputStream(new ByteArrayInputStream(src));        //文件输出流        OutputStream os = new BufferedOutputStream(new FileOutputStream(dest));        //不断的从字节数组向文件中写数据        byte[] buf = new byte[1024];        int len = 0;        while(-1 != (len = is.read(buf))) {            os.write(buf, 0, len);        }        os.flush();        //关闭流        os.close();        is.close();    }    /**     * 文件--程序-->字节数组     *      * @param srcPath     *            源文件路径     * @return 从文件获取的字节数组     * @throws IOException     */    public static byte[] getBytesFromFile(String srcPath) throws IOException {        // 创建文件源        File src = new File(srcPath);        // 创建字节数组目的地        byte[] dest = null;        // 文件输入流        InputStream is = new BufferedInputStream(new FileInputStream(src));        // 字节输出流        ByteArrayOutputStream bos = new ByteArrayOutputStream();        // 不断从文件读取数据，向字节数组写数据        byte[] buf = new byte[1024];        int len = 0;        while (-1 != (len = is.read(buf))) {            bos.write(buf, 0, len);        }        bos.flush();        dest = bos.toByteArray();        // 关闭流        bos.close();        is.close();        return dest;    }}

DataInputStream & DataOutputStream

处理流，对基本数据类型和字符串进行操作

打印流

/** * 打印流(重定向) * System.in * System.out * System.err * @author L J */public class PrintStreamDemo {    public static void main(String[] args) throws IOException {        //输出重定向,PrintStream(OutputStream out, boolean autoFlush)        //true表示自动刷出，不用手动刷出        System.setOut(new PrintStream(new BufferedOutputStream(new FileOutputStream("F:/DB/def.txt")),true));        System.out.println("哈哈");        //输出重定向到控制台        //FileDescriptor.out外必须包装一个文件输出流        //FileDescriptor.in        //FileDescriptor.err        System.setOut(new PrintStream(new BufferedOutputStream(new FileOutputStream(FileDescriptor.out)),true));        System.out.println("哈哈");    }}

装饰模式

//声音public class Voice {    private int voice = 10;    public Voice() {    }    public int getVoice() {        return voice;    }    public void setVoice(int voice) {        this.voice = voice;    }    public void say() {        System.out.println(voice);    }}

//扩音器public class Amplifier {    private Voice voice;    public Amplifier() {    }    public Amplifier(Voice voice) {        super();        this.voice = voice;    }    public void say() {        //放大音量        System.out.println(voice.getVoice() * 1000);    }}

/** * 装饰模式 * 类与类之间的关系 * 1、依赖：形参|局部变量 * 2、关联：属性 *      1)聚合：整体与部分的关系 不一致的生命周期(人与手) *      2)组合：整体与部分的关系 一致的生命周期(人与大脑) * 3、继承：父子类关系 * 4、实现：接口与实现类关系 * @author L J */public class DecoraterDemo {    public static void main(String[] args) {        Voice v = new Voice();        v.say(); //10        Amplifier am = new Amplifier(v);        am.say(); //10000    }}

文件的分割与合并

RandomAccessFile类的使用：

/** * 文件的分割与合并 * 1、分割的块数 n块 * 2、每一块的大小 blocksize * 3、最后一块文件的大小：总的文件的大小-(n-1)*blocksize * @author L J */public class RandomAccessFileDemo {    public static void main(String[] args) throws IOException {        RandomAccessFile rnd = new RandomAccessFile(new File("F:/DB/def.txt"), "r");        rnd.seek(20);        //定义缓冲大小        byte[] buf = new byte[1024];        //接收长度        int len = 0;        while(-1 != (len = rnd.read(buf))) {            if(len > 20) {                System.out.println(new String(buf, 0, 20));                break;            }else{                System.out.println(new String(buf, 0, len));            }        }        //关闭流        FileUtils.colse(rnd);    }}

文件的分割与合并：

//文件分割public class SplitFile {    //文件的路径    private String filePath;    //文件名    private String fileName;    //文件大小    private long length;    //块数    private int size;    //每块的大小    private long blocksize;    //分割后的存放目录    private String destBlockPath;    //每块的名称    private List<String> blockName;    public SplitFile() {        blockName = new ArrayList<String>();    }    public SplitFile(String filePath, String destBlockPath) {        this(filePath, destBlockPath, 1024);    }    public SplitFile(String filePath, String destBlockPath, long blockSize) {        this();        this.filePath = filePath;        this.destBlockPath = destBlockPath;        this.blocksize = blockSize;        init();    }    //确定每块的名字    private void initBlockName() {        for(int i = 0; i < size; i++) {            this.blockName.add(destBlockPath + "/" + this.fileName + i);        }    }    //初始化操作 计算块数,确定文件名和块名    public void init() {        File src = null;        //文件路径为空或不存在        if(null == filePath || !(src = new File(filePath)).exists()) {            return;        }        //文件夹        if(src.isDirectory()) {            return;        }        //文件名        this.fileName = src.getName();        //文件总大小        this.length = src.length();        //修正每块的大小        if(this.blocksize > length) {            this.blocksize = length;        }        //确定块数        size = (int)(Math.ceil(length * 1.0 / this.blocksize));        initBlockName();    }    /**     * 文件分割     * 1、第几块     * 2、起始位置     * 3、块实际大小     * @param destPath 分割后的文件存放目录     */    public void split(String destPath) {        long beginPos = 0; //起始点，默认从0开始        long actualBlocksize = blocksize; //块实际大小，默认为1024字节        for(int i = 0; i < size; i++) {            if(i == size - 1) { //最后一块                actualBlocksize = length - beginPos;            }            splitDetail(i, beginPos, actualBlocksize);            beginPos += actualBlocksize; //本次的终点，下一次的起点        }    }    /**     * 文件分割的细节     * @param index 第几块     * @param beginPos 起始位置     * @param actualBlocksize 实际大小     */    public void splitDetail(int index, long beginPos, long actualBlocksize) {        //创建源        File src = new File(this.filePath); //源文件        File dest = new File(this.blockName.get(index)); //目标文件        //选择流        RandomAccessFile raf = null;        BufferedOutputStream bos= null;        try {            raf = new RandomAccessFile(src, "r");            bos = new BufferedOutputStream(new FileOutputStream(dest));            //读取文件            raf.seek(beginPos);            //缓冲区            byte[] buf = new byte[1024];            //接收长度            int len = 0;            while(-1 != (len = raf.read(buf))) {                if(actualBlocksize - len >= 0) { //查看是否足够                    bos.write(buf, 0, len);                    actualBlocksize -= len; //剩余量                }else{                    bos.write(buf, 0, (int)actualBlocksize);                    break;                }            }        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally{            FileUtils.close(bos, raf);        }    }    //文件的合并    public void mergeFile(String destPath) {        //创建源        File dest = new File(destPath);        //选择流        BufferedOutputStream bos = null; //输出流        BufferedInputStream bis = null;  //输入流        try {            bos = new BufferedOutputStream(new FileOutputStream(dest, true));            for(int i = 0; i < this.blockName.size(); i++) {                bis = new BufferedInputStream(new FileInputStream(new File(this.blockName.get(i))));                //缓冲区                byte[] buf = new byte[1024];                //接收长度                int len = 0;                while(-1 != (len = bis.read(buf))) {                    bos.write(buf, 0, len);                }                bos.flush();                FileUtils.close(bis);            }        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally{            FileUtils.close(bos);        }    }    //文件的合并，    public void merge(String destPath) throws IOException {        //创建源        File dest = new File(destPath);        //选择流        BufferedOutputStream bos = null; //输出流        SequenceInputStream sis = null;  //输入流        //创建一个容器        Vector<InputStream> vi = new Vector<InputStream>();        for(int i = 0; i < this.blockName.size(); i++) {            vi.add(new BufferedInputStream(new FileInputStream(new File(this.blockName.get(i)))));        }        //序列输入流，需要一个枚举输入        sis = new SequenceInputStream(vi.elements());        try {            bos = new BufferedOutputStream(new FileOutputStream(dest, true));            sis = new SequenceInputStream(vi.elements());            //缓冲区            byte[] buf = new byte[1024];            //接收长度            int len = 0;            while(-1 != (len = sis.read(buf))) {                bos.write(buf, 0, len);            }            bos.flush();            FileUtils.close(sis);        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }finally{            FileUtils.close(bos);        }    }    public static void main(String[] args) throws IOException {        SplitFile splitFile = new SplitFile("F:/DB/students.xls", "F:/DB/dest",30);        splitFile.split("F:/DB/dest");        splitFile.merge("F:/DB/gh.xls");    }}