Question

How to write IO program in java?

Answer 1

Java brings different Streams with its I/O package that helps the user to perform all the input-output operations.

These streams support all the types of objects, data-types, characters, files etc to fully execute the I/O operations.

Before exploring various input and output streams lets look at 3 standard or default streams that Java has to provide which are also most common in use:

1. System.in: This is the standard input stream that is used to read characters from the keyboard or any other standard input device.
2. System.out: This is the standard output stream that is used to produce the result of a program on an output device like the computer screen.

   Here is a list of the various print functions that we use to output statements:

• print(): This method in Java is used to display a text on the console.

• println(): This method in Java is also used to display a text on the console. It prints the text on the console and the cursor moves to the start of the next line at the console.

3.System.err: This is the standard error stream that is used to output all the error data that a program might throw, on a computer screen or any standard output device.

code:

import java.io.IOException;
import java.io.InputStreamReader;

public class fileStreamTest
{
    public static void main(String args[]) throws IOException
    {
        InputStreamReader inp = null;

        inp = new InputStreamReader(System.in);

        System.out.println("Enter characters according your choice " + " and Enter '0' to         
quit.");
        char c;
        do {
            c = (char)inp.read();
            System.out.println(c);
        } while (c != '0');
    }
}

output:

Enter characters according your choice and Enter '0' to quit.
my name is Bob
m
y

n
a
m
e

i
s

B
o
b

0
0

Process finished with exit code 0

streams can be divided into two primary classes:

1) Input Stream: These streams are used to read data that must be taken as an input from a file or any peripheral device.

For eg., FileInputStream, BufferedInputStream etc.

2) Output Stream: These streams are used to write data as outputs into an array or file or any output peripheral device.

For eg., FileOutputStream , ByteArrayOutputStream etc.

code

import java.io.FileReader;
import java.io.IOException;
public class fileStreamTest
{
    public static void main(String args[]) throws IOException
    {
        FileReader sourceStream = null;
        try {
            sourceStream = new FileReader("test.txt");   //read test.text file
            int temp;
            while ((temp = sourceStream.read())!= -1)
                System.out.println((char)temp);
        }
        finally {     
         
            if (sourceStream != null) sourceStream.close();
        }
    }
}

output:

M
y

n
a
m
e

i
s

A
l
i
c
e
code(SS):

output(SS):

we can various program using IO.