Hi there,

This blog is to get you familiarize with Java file handling using java.io package. Suppose you need to read the content of your file and need to do operation on that data, in that situation you can opt to use file handling to access the data of that file.

 There are two types of stream

• InPutStream

• OutPutStream

InPutStream is used to read data from source and OutPutStream used to write data to a destination.

In this example we are going to use Byte Stream which used to perform input and output of 8-bit. To read the data of a file we will use FileInputStream class and to write FileOutputStream respectively.

Now we do the read operation on the content of file given below.

Name of my file is data.txt

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A Java program to read the content of your data.txt file using byte stream.

FileReadDemo.java

import java.io.FileInputStream;
import java.io.IOException;

public class FileReadDemo {
public static void main(String[] args) throws IOException {
 FileInputStream in = null;
 in = new FileInputStream("data.txt");
 int c;
while ((c = in.read()) != -1) {
System.out.print((char)c);
}
in.close();
}
}

put the data.txt file and FileReadDemo.java under the same directory, run the above program an the output will be printed on console.

Now the following program is to read the content of a file and write it in an another file created at run time with name output.txt.

FileReadWriteDemo.java

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileReadWriteDemo {
public static void main(String[] args) throws IOException {
 FileInputStream in = null;
 FileOutputStream out = null;
 in = new FileInputStream("data.txt");
 out = new FileOutputStream("output.txt");
 int c;
while ((c = in.read()) != -1) {
System.out.print((char)c);
out.write(c);
}
in.close();
out.close();
}
}

after running the above program the content of data.txt file will be copied in a newly created file named as output.txt with content of data.txt copied into it.