The Java.io.FileInputStream can used to convert a File object into an array of bytes. In this example, you read a file from “C:\\testing.txt“, convert it into an array of bytes and print out the content.

package com.mkyong.common;
 
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
 
public class FileToArrayOfBytes
{
    public static void main( String[] args )
    {
    	FileInputStream fileInputStream=null;
 
        File file = new File("C:\\testing.txt");
 
        byte[] bFile = new byte[(int) file.length()];
 
        try {
            //convert file into array of bytes
	    fileInputStream = new FileInputStream(file);
	    fileInputStream.read(bFile);
	    fileInputStream.close();
 
	    for (int i = 0; i < bFile.length; i++) {
	       	System.out.print((char)bFile[i]);
            }
 
	    System.out.println("Done");
        }catch(Exception e){
        	e.printStackTrace();
        }
    }
}
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