Tuesday 5 February 2019

java - 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();
}

Answer



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.


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