Using Collections to Reverse the Byte[] Order

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Hi, I am using collections to reverse the order but it does not seem to work. Could you tell me what I am doing wrong. Thanks, Alex

package com.codegym.task.task18.task1809; /* Reversing a file */ import java.io.BufferedReader; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStreamReader; import java.util.Collections; import java.util.Arrays; public class Solution { public static void main(String[] args) { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); try{ String file1 = reader.readLine(); String file2 = reader.readLine(); FileInputStream inputStream = new FileInputStream(file1); FileOutputStream outputStream = new FileOutputStream(file2); byte[] fullData = new byte[inputStream.available()]; Collections.reverse(Arrays.asList(fullData)); outputStream.write(fullData); inputStream.close(); outputStream.close(); }catch(Exception e){ e.printStackTrace(); } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

22 January 2020, 20:26

This is because 'byte' is a primitive and cannot be converted to a Collection (to be used with the Collections class). Try typing code like this into intelliJ: ArrayList<byte> temp = new ArrayList<>; and you will get an error saying the same. Using your logic, you can convert this to a string and use the StringBuilder class to accomplish the same thing like this:

byte[] fullData = new byte[inputStream.available()];
StringBuilder sb = new StringBuilder(new String(fullData));
sb.reverse();
outputStream.write(sb.toString().getBytes());

Another problem with this code is that the data is never read in. Line 25 creates a buffer but ther e is not nowhere in this code where .read() is called.