Java NIO 之 FileChannel 的使用

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FileInputStream fis = new FileInputStream("/Users/peiel/a.txt");
FileChannel fileChannel = fis.getChannel();

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RandomAccessFile fis = new RandomAccessFile("/Users/peiel/a.txt", "rw");
FileChannel fileChannel = fis.getChannel();

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ByteBuffer buf = ByteBuffer.allocate(4);

int len;
while ((len = fileChannel.read(buf)) != -1) {
    // flip buf (limit = position; position = 0;)
    buf.flip();
    // 方式一：转换成数组读取的方式
    System.out.print(new String(buf.array(), 0, len));
    // 方式二：直接读取的方式
    while (buf.hasRemaining()) {
        System.out.print((char) buf.get());
    }
    // clear    
    buf.clear();
}

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String newData = "This is a boy!";

ByteBuffer byteBuffer = ByteBuffer.allocate(16);
byteBuffer.clear();
byteBuffer.put(newData.getBytes());

byteBuffer.flip();
while (byteBuffer.hasRemaining()) {
    fileChannel.write(byteBuffer);
}