Using the unsafe versions of add/get to improve performance.
Here are some numbers for 2^15 intersections of two random
sorted lists with 16k elements. The numbers were gathered with
perf stat -d -d -d --delay 2000 java -ea -cp bin/test:bin/main
org.lucares.collections.Test 16000 15 (the test class is not committed)
Duration: 9059ms -> 7293ms (80.5%)
Cycles: 26.084.812.051 -> 21.616.608.207 (82.9%)
Instructions: 68.045.848.666 -> 52.306.000.150 (76.9%)
Instructions per Cycle: 2,61 -> 2.42
Branches: 15.007.093.940 -> 9.839.481.658 (65.6%)
Branch Misses: 2.285.461 -> 1.551.906
Cycles per element: 24.87 -> 20.61 (82.9%)