进一步有进一步惊喜

public interface FilenameFilter{
  boolean accept(File dir, String name);
}

File f = new File(".\\pom.xml");
System.out.println(f.getParent());
System.out.println(f.getName());
System.out.println(f.getPath());
System.out.println(f.getAbsolutePath());
System.out.println(f.getCanonicalPath());

public static String
read(String filename){
  BufferReader in = new BufferReader(
    new FileReader(filename)
  );
  String s;
  StringBuilder sb = new StringBuilder();
  while(s = in.readLine() != null){
    sb.append(s+"\n");
    // 使用如下代码是否更好？
    /*
    sb.append(s);
    sb.append("\n");
    */
  }
  in.close();
  return sb.toString();
}

StringReader in = new StringReader(
  BufferedInputFile.read(filename)
);
int c;
// 从内存缓冲区读取文件的字节数据。
while((c = in.read()) != -1){
  System.out.print((char)c);
}

DataInputSteam in = new DataInputStream(
  new ByteArrayInputStream(
    BufferedInputFile.read(filename).getBytes()
  )
);
while(in.available() != 0){
  System.out.print((char)in.readBytes());
}

PrintWriter out = new PrintWriter(
  new BufferedWriter(new FileWriter(filename))
);
// 将内容输出到文件中
out.println(str);

String filename = "Hello.java";
PrintWriter out = new PrintWriter(filename);

BufferedReader stdin = new BufferedRead(
  new InputStreamReader(System.in)
);
String s;
while((s = std.readLine()) != null && s.length() != 0){
  System.out.println(s);
}

// true 自动清空
PrintWriter out = new PrintWriter(System.out,true);

// comnands 是运行命令的String[]
Process process = new ProcessBuilder(commands).start();
// 获得运行的输出结果
BufferedRead result = new BufferedReader(new InputStreamReader(process.getInputStream()));
// 获得程序运行的错误
BufferedReader errors = new BufferedReader(new InputStreamReader(process.getErrorStream()))

// 使用文件通道写入数据
FileChannels fc = new FileOutputStream(filename).getChannel();
// 写入字节数组
Byte[] bytes = "Hello".getBytes();
fc.write(ByteBuffer.wrap(bytes));
fc.close();
// 通过文件通道读取数据
fc = new FileInputStream(filename).getChannel();
// 分配缓冲区大小
ByteBuffer buff = ByteBuffer.allocate(SIZE);
fc.read(buff);
// flip()作用是告诉外部,可以读取缓冲中的字节数据了。
buff.flip();
while(buff.hasRemaining()){
  // 将字节数据转成字符
  System.out.print((char)buff.get());
}

// 常量缓冲区的大小
final int BSIZE = 1024;
FileChannel
  in = new FileInputStream(source).getChannel(),
  out = new FileOutputStream(dest).getChannel();
// 缓冲区
ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
while(in.read(buffer) != -1){
  // -1标志为读取数据结束
  // 准备好写
  buffer.flip();
  out.write(buffer);
  // 准备好读
  buffer.clear();
}

// in => out
in.transferTo(0,in.size(),out);
// or 
// out.transferFrom(in,0,in.size());

CharBuffer cb = ((ByteBuffer)bb.rewind()).asCharBuffer();
// 读取Char数据
while(cb.hasRemaining()){
  System.out.print(cb.position() + "->" + cb.get()+ ",");
}

FloatBuffer fb = ((ByteBuffer)bb.rewind()).asFloatBuffer();
IntBuffer ib = ((ByteBuffer)bb.rewind()).asIntBuffer();
ShortBuffer sb = ((ByteBuffer)bb.rewind()).asShortBuffer();
LongBuffer lb = ((ByteBuffer)bb.rewind()).asLongBuffer();
DoubleBuffer db = ((ByteBuffer)bb.rewind()).asDoubleBuffer();

// 高位优先
bb.order(ByteOrder.BIG_ENDIAN);
// 低位优先
bb.order(ByteOrder.LITTLE_ENDIAN);

public class UsingBuffers {
    private static void symmetricScramble(CharBuffer buffer){
       while (buffer.hasRemaining()){
           // 做标记
           buffer.mark();
           char c1 = buffer.get();
           char c2 = buffer.get();
           // 回到标记点
           buffer.reset();
           // 交换次序存储
           buffer.put(c2).put(c1);
       }
    }

    public static void main(String[] args) {
        char[] data = "UsingBuffers".toCharArray();
        // 一个字符占有两个字节
        ByteBuffer bb = ByteBuffer.allocate(data.length*2);
        CharBuffer cb = bb.asCharBuffer();
        cb.put(data);
        System.out.println(cb.rewind());
        // 交换
        symmetricScramble(cb);
        System.out.println(cb.rewind());
        // 交换
        symmetricScramble(cb);
        System.out.println(cb.rewind());
    }
}

FileChannel fc = new RandomAccessFile("temp.tmp","rw").getChannel();
IntBuffer ib = fc.map(FileChannel.MapMode.READ_WRITE,0,fc.size()).asIntBuffer();
// 使用通道写入数据
for (int i = 0; i < numOfInts; i++) {
    ib.put(i);
}
fc.close();

FileChannel fc = new FileInputStream(new File("temp.tmp")).getChannel();
IntBuffer ib = fc.map(FileChannel.MapMode.READ_ONLY,0,fc.size()).asIntBuffer();
while (ib.hasRemaining()){
    ib.get();
}
fc.close();