java.io package

contain all classes that are required to handle input and output

character stream

reader and writer stream are character stream

byte stream

Input and output stream are byte stream.eg:images ,sounds.
2 types:
1.ObjectInputStream
2.ObjectOutputStram

System.err

System is a class in java.lang package and contain a predefined stream variable err.
refers to standard error stream which is also console

it is object of type PrintStream.
it is a byte stream.

System.in

System is a class in java.lang package and has a predefined stream variable in.
refers to standard input that is keyboard.
it is an object of type input stream.

it is a byte stream

System.out

System is the class name and out is a predefined stream variable.
refers to standard output stream which is console
it is object of type PrintStream.
it is a byte stream.

stream

java provide input and output through stream.
Streams are ordered sequence of data that have a source or destination. two categories
1.character stream
2.byte stream