Java – Why does this code using random strings print “hello world”

javarandomstring

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();
}

Best Solution

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
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