How to Read Integers From a File in Java

To read integers from a file, we use BufferedReader to read the file and the parseInt() method to get the integers from the data. This tutorial demonstrates a step-by-step process of how to read integers from a file in Java.

Read Integers From a File in Java

The BufferedReader class is used to perform the read and stream of characters from the files or other sources in Java. The BufferedReader class has a method readline(), which reads every next line and returns a string.

The class BufferedReader doesn’t provide any method to read the integer from a file, so initially, we read integers as strings, then we use the method parseInt() to parse the string into an integer. The step-by-step process of the whole method is given below.

Let’s implement the steps in Java code.

package delftstack;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Read_Integer {
  public static void main(String args[]) throws IOException {
    BufferedReader reader = new BufferedReader(new FileReader("delftstack.txt"));

    String Int_line;

    while ((Int_line = reader.readLine()) != null) {
      int In_Value = Integer.parseInt(Int_line);
      // Print the Integer
      System.out.println(Int_line);
    }
  }
}

The file we are trying to read is:

The output for the code will be:

1
12
123
1234
12345
123456
1234567
12345678
123456789
1234567890