java中InputStream获取字节大小相关方法详解

InputStream is = this.getClass().getResourceAsStream(filePath);
byte[] bytes = StreamUtils.copyToByteArray(is);
is.read(bytes);

InputStream is = this.getClass().getResourceAsStream(filePath);
byte[] bytes = new byte[is.available()];
is.read(bytes);

/**
 * Returns an estimate of the number of bytes that can be read (or
 * skipped over) from this input stream without blocking by the next
 * invocation of a method for this input stream. The next invocation
 * might be the same thread or another thread.  A single read or skip of this
 * many bytes will not block, but may read or skip fewer bytes.
 *
 * <p> Note that while some implementations of {@code InputStream} will return
 * the total number of bytes in the stream, many will not.  It is
 * never correct to use the return value of this method to allocate
 * a buffer intended to hold all data in this stream.
 *
 * <p> A subclass' implementation of this method may choose to throw an
 * {@link java.io.IOException} if this input stream has been closed by
 * invoking the {@link #close()} method.
 *
 * <p> The {@code available} method for class {@code InputStream} always
 * returns {@code 0}.
 *
 * <p> This method should be overridden by subclasses.
 *
 * @return     an estimate of the number of bytes that can be read (or skipped
 *             over) from this input stream without blocking or {@code 0} when
 *             it reaches the end of the input stream.
 * @exception java.io.IOException if an I/O error occurs.
 */

File file = new File(path);
InputStream stream = new FileInputStream(file);
byte[] bytes = new byte[file.length()]