Why does this code using random strings print "hello world"?

Question

The following print statement would print "hello world". Could anyone explain this?

System.out.println(randomString(-229985452) + " " + randomString(-147909649)); 

And randomString() looks like this:

public static String randomString(int i) {     Random ran = new Random(i);     StringBuilder sb = new StringBuilder();     while (true)     {         int k = ran.nextInt(27);         if (k == 0)             break;          sb.append((char)('`' + k));     }      return sb.toString(); } 

Answer 1

The other answers explain why, but here is how.

Given an instance of Random:

Random r = new Random(-229985452) 

The first 6 numbers that r.nextInt(27) generates are:

8 5 12 12 15 0 

and the first 6 numbers that r.nextInt(27) generates given Random r = new Random(-147909649) are:

23 15 18 12 4 0 

Then just add those numbers to the integer representation of the character ` (which is 96):

8  + 96 = 104 --> h 5  + 96 = 101 --> e 12 + 96 = 108 --> l 12 + 96 = 108 --> l 15 + 96 = 111 --> o  23 + 96 = 119 --> w 15 + 96 = 111 --> o 18 + 96 = 114 --> r 12 + 96 = 108 --> l 4  + 96 = 100 --> d 

Answer 2

When an instance of java.util.Random is constructed with a specific seed parameter (in this case -229985452 or -147909649), it follows the random number generation algorithm beginning with that seed value.

Every Random constructed with the same seed will generate the same pattern of numbers every time.