echauchot commented on a change in pull request #4143: Faster implementation of
nexmark.Generator.nextExactString().
URL: https://github.com/apache/beam/pull/4143#discussion_r152771825
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File path:
sdks/java/nexmark/src/main/java/org/apache/beam/sdk/nexmark/sources/Generator.java
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@@ -353,8 +353,16 @@ private static String nextString(Random random, int
maxLength) {
/** Return a random string of exactly {@code length}. */
private static String nextExactString(Random random, int length) {
StringBuilder sb = new StringBuilder();
+ int rnd = 0;
+ int n = 0; // number of random characters left in rnd
while (length-- > 0) {
- sb.append((char) ('a' + random.nextInt(26)));
+ if (n == 0) {
+ rnd = random.nextInt();
+ n = 6; // log_26(2^31)
+ }
+ sb.append((char) ('a' + rnd % 26));
+ rnd /= 26;
Review comment:
We will concatenate ints between 0 and 25 as before. But if `rnd` happens to
be < 26 then it will be set in this line to 0 for the next `n` iterations (6 at
worse) leading to appending 0 to `sb`. So there will be a more probable 0 than
previous implementation. Consider using `Random.intervalNextInt(length*26,
Integer.MAX_VALUE)`. But it might be not a big deal
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