Write a short note on FilelnputStream and FileOutputStream class.

FileInputStream and FileOutputStream are two classes provided by Java for reading data from and writing data to a file, respectively. They are part of Java's I/O streams framework which is used to handle input and output operations.

1. FileInputStream: This is an input stream used for reading data from a file. It is used to read byte-oriented data (streams of raw bytes such as image data, etc.). If the file does not exist, a FileNotFoundException is thrown. Here is a simple usage example:

FileInputStream fis = new FileInputStream("input.txt");
int i = fis.read();
while(i != -1) {
    System.out.print((char)i);
    i = fis.read();
}
fis.close();

In this example, we're creating a FileInputStream on the file "input.txt", reading one byte at a time from the file, and then printing out the data as characters. The read() method returns -1 when there is no more data to read.

2. FileOutputStream: This is an output stream used for writing data to a file. Like FileInputStream, it is used for writing byte-oriented data. If the file does not exist, one will be created. Here is a simple usage example:

FileOutputStream fos = new FileOutputStream("output.txt");
String data = "Hello, world!";
fos.write(data.getBytes());
fos.close();

In this example, we're creating a FileOutputStream on the file "output.txt", converting a string to bytes using the getBytes() method, and then writing those bytes to the file.

Both FileInputStream and FileOutputStream should always be closed after use to free up system resources. This can be done using the close() method, or by using a try-with-resources statement which automatically closes the streams.