JAVA I/O

ava I/O (Input and Output) is used to process the input and produce the output based on the input.

Java uses the concept of stream to make I/O operation fast. The java.io package contains all the classes required for input and output operations.

We can perform file handling in java by java IO API.

Stream

A stream is a sequence of data.In Java a stream is composed of bytes. It's called a stream because it's like a stream of water that continues to flow.

In java, 3 streams are created for us automatically. All these streams are attached with console.

1) System.out: standard output stream

2) System.in: standard input stream

3) System.err: standard error stream

Let's see the code to print output and error message to the console.

1. System.out.println("simple message");  
2. System.err.println("error message");  

Let's see the code to get input from console.

1. int i=System.in.read();//returns ASCII code of 1st character  
2. System.out.println((char)i);//will print the character