Why does this code using random strings print “hello world”?
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();
}
2Answer
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.
- answered 8 years ago
- Sandy Hook
The other answers explain why, but here is how:
new Random(-229985452).nextInt(27)
The first 6 numbers that the above random generates are:
8
5
12
12
15
0
and the first 6 numbers that new Random(-147909649).nextInt(27) generates 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
- answered 8 years ago
- Gul Hafiz
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