I'm using Eclipse 2020-03 (4.15.0) with Sonarlint for Eclipse 5.1.0.17086 and I get , IMO, false positive S1854 warnings in the following code (taken from the book "Java 8 In Action"). Working with Java OpenJDK 13.0.2. This is not a showstopper since I am merely studying Java 8 techniques. I just want to understand why these lines are flagged...
package nl.paul.forkjoin;
import java.util.concurrent.RecursiveTask;
public class ForkJoinSumCalculator extends RecursiveTask<Long> {
private static final long serialVersionUID = 1L;
private final long[] numbers;
private final int start;
private final int end;
public static final long THRESHOLD = 10_000;
public ForkJoinSumCalculator(long[] numbers) {
this(numbers, 0, numbers.length);
}
private ForkJoinSumCalculator(long[] numbers, int start, int end) {
this.numbers = numbers;
this.start = start;
this.end = end;
}
@Override
protected Long compute() {
int length = end - start; //SonarLint S1854 warning
if (length <= THRESHOLD) {
return computeSequentially();
}
ForkJoinSumCalculator leftTask = new ForkJoinSumCalculator(numbers, start, start + length / 2); //SonarLint S1854 warning
ForkJoinSumCalculator rightTask = new ForkJoinSumCalculator(numbers, start + length / 2, end); //SonarLint S1854 warning
leftTask.fork();
return leftTask.join() + rightTask.compute();
}
private long computeSequentially() {
long sum = 0;
for (int i = start; i < end; i++) {
sum += numbers[i];
}
return sum;
}
}
Did I miss something here? Both "length", "leftTask" and "rightTask" are used several times in the code...
Above class is tested with the following class:
package nl.paul.forkjoin;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.stream.LongStream;
public class ForkJoinTest {
public static void main(String[] args) {
System.out.println(new ForkJoinTest().doIt(10_000_000));
}
private long doIt(long n) {
long[] numbers = LongStream.rangeClosed(0, n).toArray();
long start = System.currentTimeMillis();
ForkJoinTask<Long> task = new ForkJoinSumCalculator(numbers);
long result = new ForkJoinPool().invoke(task);
long finish = System.currentTimeMillis();
System.out.println("Processing took " + (finish - start) + " msec.");
return result;
}
}
