JDK 中高效的实现

 

记录一下

 

/**
     * See the general contract of the <code>readInt</code>
     * method of <code>DataInput</code>.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next four bytes of this input stream, interpreted as an
     *             <code>int</code>.
     * @exception  EOFException  if this input stream reaches the end before
     *               reading four bytes.
     * @exception  IOException   the stream has been closed and the contained
     * 		   input stream does not support reading after close, or
     * 		   another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final int readInt() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        int ch3 = in.read();
        int ch4 = in.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }