Java read inputstream byte by byte

Class ByteArrayInputStream

A ByteArrayInputStream contains an internal buffer that contains bytes that may be read from the stream. An internal counter keeps track of the next byte to be supplied by the read method.

Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException .

Field Summary

Constructor Summary

Method Summary

Methods declared in class java.io.InputStream

Methods declared in class java.lang.Object

Field Details

buf

An array of bytes that was provided by the creator of the stream. Elements buf[0] through buf[count-1] are the only bytes that can ever be read from the stream; element buf[pos] is the next byte to be read.

pos

The index of the next character to read from the input stream buffer. This value should always be nonnegative and not larger than the value of count . The next byte to be read from the input stream buffer will be buf[pos] .

mark

The currently marked position in the stream. ByteArrayInputStream objects are marked at position zero by default when constructed. They may be marked at another position within the buffer by the mark() method. The current buffer position is set to this point by the reset() method. If no mark has been set, then the value of mark is the offset passed to the constructor (or 0 if the offset was not supplied).

count

The index one greater than the last valid character in the input stream buffer. This value should always be nonnegative and not larger than the length of buf . It is one greater than the position of the last byte within buf that can ever be read from the input stream buffer.

Constructor Details

ByteArrayInputStream

Creates a ByteArrayInputStream so that it uses buf as its buffer array. The buffer array is not copied. The initial value of pos is 0 and the initial value of count is the length of buf .

ByteArrayInputStream

Creates ByteArrayInputStream that uses buf as its buffer array. The initial value of pos is offset and the initial value of count is the minimum of offset+length and buf.length . The buffer array is not copied. The buffer’s mark is set to the specified offset.

Method Details

read

Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255 . If no byte is available because the end of the stream has been reached, the value -1 is returned. This read method cannot block.

read

Reads up to len bytes of data into an array of bytes from this input stream. If pos equals count , then -1 is returned to indicate end of file. Otherwise, the number k of bytes read is equal to the smaller of len and count-pos . If k is positive, then bytes buf[pos] through buf[pos+k-1] are copied into b[off] through b[off+k-1] in the manner performed by System.arraycopy . The value k is added into pos and k is returned. Unlike the overridden method of InputStream , this method returns -1 instead of zero if the end of the stream has been reached and len == 0 . This read method cannot block.

readAllBytes

Reads all remaining bytes from the input stream. This method blocks until all remaining bytes have been read and end of stream is detected, or an exception is thrown. This method does not close the input stream. When this stream reaches end of stream, further invocations of this method will return an empty byte array. Note that this method is intended for simple cases where it is convenient to read all bytes into a byte array. It is not intended for reading input streams with large amounts of data. The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified. If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.

readNBytes

Reads the requested number of bytes from the input stream into the given byte array. This method blocks until len bytes of input data have been read, end of stream is detected, or an exception is thrown. The number of bytes actually read, possibly zero, is returned. This method does not close the input stream. In the case where end of stream is reached before len bytes have been read, then the actual number of bytes read will be returned. When this stream reaches end of stream, further invocations of this method will return zero. If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read up to len bytes. The first byte read is stored into element b[off] , the next one in to b[off+1] , and so on. The number of bytes read is, at most, equal to len . Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+ k -1] , leaving elements b[off+ k ] through b[off+len-1] unaffected. The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified. If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes of b have been updated with data from the input stream. Consequently the input stream and b may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.

skip

Skips n bytes of input from this input stream. Fewer bytes might be skipped if the end of the input stream is reached. The actual number k of bytes to be skipped is equal to the smaller of n and count-pos . The value k is added into pos and k is returned.

available

Returns the number of remaining bytes that can be read (or skipped over) from this input stream. The value returned is count — pos , which is the number of bytes remaining to be read from the input buffer.

markSupported

mark

Set the current marked position in the stream. ByteArrayInputStream objects are marked at position zero by default when constructed. They may be marked at another position within the buffer by this method. If no mark has been set, then the value of the mark is the offset passed to the constructor (or 0 if the offset was not supplied). Note: The readAheadLimit for this class has no meaning.

reset

Resets the buffer to the marked position. The marked position is 0 unless another position was marked or an offset was specified in the constructor.

close

Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException .

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