Java IO 对字符的读取和写出

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1、对字符的读取

只能读取纯文本，不能读取二进制文件如音频，视频等，doc文件以及其他不是纯文本的文档。

1.1 纯文本的读取

使用java.io.Reader类读取纯文本文件，其源代码重要的几个方法如下：

package java.io;public abstract class Reader implements Readable, Closeable {    /**     * 读取一个字符     */    public int read() throws IOException {        char cb[] = new char[1];        if (read(cb, 0, 1) == -1)            return -1;        else            return cb[0];    }    /**     * 读取一个字符数组     */    public int read(char cbuf[]) throws IOException {        return read(cbuf, 0, cbuf.length);    }    /**     * 读取一个字符数组或者字符数组的一部分     */    abstract public int read(char cbuf[], int off, int len) throws IOException;    /**     * 关闭流     */     abstract public void close() throws IOException;}

1.2 读取纯文本的demo如下：

/** *  * @param file *            文件对象 */public static void readFile(File file) {    Reader reader = null;    try {        reader = new FileReader(file);        char[] buffer = new char[1024];        int len = 0;        while (-1 != (len = reader.read(buffer))) {            System.out.println(new String(buffer, 0, len));        }    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    } finally {        try {            if (null != reader) {                reader.close();            }        } catch (IOException e) {            e.printStackTrace();        }    }}/** *  * @param file *            文件对象 */public static void readFileWithJdk7(File file) {    // java 7 新特性 try-with-resource    // 不用手动释放资源，程序自动释放，因为Reader实现了AutoCloseable接口    try (Reader reader = new FileReader(file)) {        char[] buffer = new char[1024];        int len = 0;        while (-1 != (len = reader.read(buffer))) {            System.out.println(new String(buffer, 0, len));        }    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    }}/** *  * @param filePath *            文件路径 */public static void readFile(String filePath) {    readFile(new File(filePath));}

2、对字符的写出

只能对纯文本写出。

2.1 纯文本的写出

使用java.io.Writer类向纯文本进行写出，其中源码几个重要的方法如下：

package java.io;public abstract class Writer implements Appendable, Closeable, Flushable {    /**     * 写一个字符     */    public void write(int c) throws IOException {        synchronized (lock) {            if (writeBuffer == null){                writeBuffer = new char[WRITE_BUFFER_SIZE];            }            writeBuffer[0] = (char) c;            write(writeBuffer, 0, 1);        }    }    /**     * 写一个字符数组     */    public void write(char cbuf[]) throws IOException {        write(cbuf, 0, cbuf.length);    }    /**     *写一个字符数组或字符数组的一部分     */    abstract public void write(char cbuf[], int off, int len) throws IOException;    /**     * 写一个字符串     */    public void write(String str) throws IOException {        write(str, 0, str.length());    }    /**     * 写一个字符串或字符串的一部分     */    public void write(String str, int off, int len) throws IOException {        synchronized (lock) {            char cbuf[];            if (len <= WRITE_BUFFER_SIZE) {                if (writeBuffer == null) {                    writeBuffer = new char[WRITE_BUFFER_SIZE];                }                cbuf = writeBuffer;            } else {    // Don't permanently allocate very large buffers.                cbuf = new char[len];            }            str.getChars(off, (off + len), cbuf, 0);            write(cbuf, 0, len);        }    }    /**     * 追加特定字符到此流中     */    public Writer append(CharSequence csq) throws IOException {        if (csq == null)            write("null");        else            write(csq.toString());        return this;    }    /**     * 追加特定字符或特定字符的一部分到此流中     */    public Writer append(CharSequence csq, int start, int end) throws IOException {        CharSequence cs = (csq == null ? "null" : csq);        write(cs.subSequence(start, end).toString());        return this;    }    /**     * 追加特定字符到此流中     */    public Writer append(char c) throws IOException {        write(c);        return this;    }    /**     * 刷新流     */    abstract public void flush() throws IOException;    /**     * 关闭流     */    abstract public void close() throws IOException;}

2.2 纯文本写出demo如下：

/** * jdk 7 新特性 *  * @param file *            指定输出文件 * @param msg *            输出内容 * @param append *            是否追加，true 追加 false 不追加 */public static void writeToFileWithJdk7(File file, String msg, boolean append) {    try (Writer writer = new FileWriter(file)) {        writer.write(msg);        writer.flush();    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    }}/** *  * @param file *            指定输出文件 * @param msg *            输出内容 * @param append *            是否追加，true 追加 false 不追加 */public static void writeToFile(File file, String msg, boolean append) {    Writer writer = null;    try {        writer = new FileWriter(file);        writer.write(msg);        writer.flush();    } catch (FileNotFoundException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    } finally {        try {            if (null != writer) {                writer.close();            }        } catch (IOException e) {            e.printStackTrace();        }    }}/** *  * @param filePath *            指定输出文件路径 * @param msg *            输出内容 * @param append *            是否追加，true 追加 false 不追加 */public static void writeToFile(String filePath, String msg, boolean append) {    writeToFile(new File(filePath), msg, append);}

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