If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at the end of the file, the value -1 is returned; otherwise, at least one byte is read and stored into b. The first byte read is stored into element b[0] , the next one into b[1] , and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[ k -1] , leaving elements b[ k ] through b[b.
The read b method for class InputStream has the same effect as: read b, 0, b. Returns: the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached. NullPointerException - if b is null. See Also: read byte[], int, int read public int read byte[] b, int off, int len throws IOException Reads up to len bytes of data from the input stream into an array of bytes.
An attempt is made to read as many as len bytes, but a smaller number may be read. If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b. The number of bytes read is, at most, equal to len. The read b, off, len method for class InputStream simply calls the method read repeatedly.
If the first such call results in an IOException , that exception is returned from the call to the read b, off, len method. If any subsequent call to read results in a IOException , the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned.
The default implementation of this method blocks until the requested amount of input data len has been read, end of file is detected, or an exception is thrown. Subclasses are encouraged to provide a more efficient implementation of this method. Parameters: b - the buffer into which the data is read. In our examples we use try-with-resources statement, which ensures that each resource is closed at the end of the statement. FileInputStream is a specialization of the InputStream for reading bytes from a file.
InputStreamReader is a bridge from byte streams to character streams: it reads bytes and decodes them into characters using a specified charset. BufferedReader reads text from a character-input stream, buffering characters for efficient reading of characters, arrays, and lines. Discussion Forums. Course Information. Unit 1: Introduction. Unit 2: Object-Oriented Programming. Unit 3: Java in Practice. Unit 4: Relational and Logical Operators in Java.
Unit 5: Control Structures. Unit 6: User-Defined Methods. Unit 7: Arrays. From the Java Tutorial :. A program uses an input stream to read data from a source, one item at a time:. A program uses an output stream to write data to a destination, one item at time:. The data source and data destination pictured above can be anything that holds, generates, or consumes data. Obviously this includes disk files , but a source or destination can also be another program, a peripheral device, a network socket, or an array.
Sample code from oracle tutorial:. This program uses byte streams to copy xanadu. Have a look at this SE question to know more details about advanced Character streams, which are wrappers on top of Byte Streams :.
OutputStream is an abstract class that represents writing output. There are many different OutputStream classes, and they write out to certain things like the screen, or Files, or byte arrays, or network connections, or etc. InputStream classes access the same things, but they read data in from them.
Here is a good basic example of using FileOutputStream and FileInputStream to write data to a file, then read it back in. Java stream is a flow of data from a source into a destination. The source or destination can be a disk, memory, socket, or other programs. The data can be bytes, characters, or objects. A good metaphor for Java streams is water flowing from a tap into a bathtub and later into a drainage. The data represents the static part of the stream; the read and write methods the dynamic part of the stream.
InputStream represents a flow of data from the source, the OutputStream represents a flow of data into the destination. Finally, InputStream and OutputStream are abstractions over low-level access to data, such as C file pointers. Stream : In laymen terms stream is data , most generic stream is binary representation of data. Input Stream : If you are reading data from a file or any other source , stream used is input stream. In a simpler terms input stream acts as a channel to read data.
Output Stream : If you want to read and process data from a source file etc you first need to save the data , the mean to store data is output stream. An output stream is generally related to some data destination like a file or a network etc. In java output stream is a destination where data is eventually written and it ends. For one kind of InputStream, you can think of it as a "representation" of a data source, like a file.
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