File inputStream in Java

As we discussed earlier, A stream can be defined as a sequence of data. The InputStream is used to read data from a source and the OutputStream is used for writing data to a destination. Here is a hierarchy of classes to deal with Input and Output streams.
The two important streams are FileInputStream and FileOutputStream which would be discussed in this tutorial:

FileInputStream
This stream is used for reading data from the files. Objects can be created using the keyword new and there are several types of constructors available.

Following constructor takes a file name as a string to create an input stream object to read the file:
InputStream f = new FileInputStream("C:/java/hello");

Following constructor takes a file object to create an input stream object to read the file. First we create a file object using File() method as follows:
File f = new File("C:/java/hello");
InputStream f = new FileInputStream(f);

DataInputStream
The DataInputStream is used in the context of DataOutputStream and can be used to read primitives.
Following is the constructor to create an InputStream:
InputStream in = DataInputStream(InputStream in);

Example:
Following is the example to demonstrate DataInputStream. This example reads 5 lines given in a file test.txt and converts those lines into capital letters and finally copies them into another file test1.txt.

import java.io.*;
public class Test{
public static void main(String args[])throws IOException{
DataInputStream d = new DataInputStream(new
FileInputStream("test.txt"));
DataOutputStream out = new DataOutputStream(new
FileOutputStream("test1.txt"));
String count;
while((count = d.readLine()) != null){
String u = count.toUpperCase();
System.out.println(u);
out.writeBytes(u + " ,");
}
d.close();
out.close();
}
}