Indexoutofboundsexception in reading an Inputstream

Question

follows the excerpt of the code I am studying:

FileInputStream stream = new FileInputStream("/home/rafael/2015.json"); // esse aquivo tem 24 bytes

byte[] result = new byte[(int) stream.getChannel().size()];

int offset = 0;
int read = 0;

while((read = stream.read(result, offset, 8)) != -1){
    offset += read;
}

stream.close();

But I’ve been getting the following exception:

Exception in thread "main" java.lang.IndexOutOfBoundsException
    at java.io.FileInputStream.readBytes(Native Method)
    at java.io.FileInputStream.read(FileInputStream.java:272)
    at br.com.rafael.socket.Main.main(Main.java:17)

I have checked my offset, and it works correctly. What can be?

-- adding a debug

FileInputStream stream = new FileInputStream("/home/rafael/2015.json");

byte[] result = new byte[(int) stream.getChannel().size()];

int offset = 0;
int read = 0;

while((read = stream.read(result, offset, 8)) != -1){
    offset += read;

    System.out.println("read: " + read);
    System.out.println("offset: " + offset);
}

System.out.println("o que foi lido? " + new String(result, "UTF-8"));

stream.close();

console:

read: 8
offset: 8
read: 8
offset: 16
read: 8
offset: 24
Exception in thread "main" java.lang.IndexOutOfBoundsException
    at java.io.FileInputStream.readBytes(Native Method)
    at java.io.FileInputStream.read(FileInputStream.java:272)
    at br.com.rafael.socket.Main.main(Main.java:17)

-- adding remanufacturing:

1º decreases the reading size to 1 byte / iteration

while((read = stream.read(result, offset += read, 1)) != -1){}

2º I increased the result array in 1 index

byte[] result = new byte[stream.available() + 1];

and now it worked perfectly:

HOWEVER i get the last input of my array result with the value 0

-- best solution

FileInputStream stream = new FileInputStream("/home/rafael/2015");

byte[] result = new byte[stream.available()];

int offset = 0;
int read = 0;
int buffer = 256;
int remain = result.length;

while((remain -= read = stream.read(result, offset += read, buffer >= remain ? remain : buffer)) > 0){}         

stream.close();

Answer 1

Change the size added to the byte array, the set value is smaller than it should be, so as it iterates, when it reaches a certain value, the IndexOutOfBoundsException use the read method()

byte[] result = new byte[stream.read()];

But if you still want the previous value, instead of using

byte[] result = new byte[(int) stream.getChannel().size()];

use

byte[] result = new byte[stream.available()];