How to assign file content into a variable in Java

Most people will read the file content and assign to StringBuffer or String line by line. Here’s another trick that may interest you – how to assign whole file content into a variable with one Java’s statement, try it :)

Example

In this example, you will use DataInputStreamto convert all the content into bytes, and create a String variable with the converted bytes.

package com.mkyong.io;
 
import java.io.DataInputStream;
import java.io.FileInputStream;
 
public class App{
 
 public static void main (String args[]) {
 
 try{
 
          DataInputStream dis = 
      new DataInputStream (
        new FileInputStream ("c:\\logging.log"));
 
   byte[] datainBytes = new byte[dis.available()];
   dis.readFully(datainBytes);
   dis.close();
 
   String content = new String(datainBytes, 0, datainBytes.length);
 
   System.out.println(content);
 
 }catch(Exception ex){
  ex.printStackTrace();
 }
 
  }
}

Output

This will print out all the “logging.log” file content.

10:21:29,425  INFO Version:15 - Hibernate Annotations 3.3.0.GA
10:21:29,441  INFO Environment:509 - Hibernate 3.2.3
10:21:29,441  INFO Environment:542 - hibernate.properties not found
10:21:29,456  INFO Environment:676 - Bytecode provider name : cglib
10:21:29,456  INFO Environment:593 - using JDK 1.4 java.sql.Timestamp handling
............