@org.junit.jupiter.api.Test
public void compareArrayListAndHashMapAndSet1(){
Map<Long, Long> map = new HashMap<>();
for (int i = 0; i < 1000_0000; i++) {
map.put(i+1L, i+1L);
}
long start = System.currentTimeMillis();
for (int i = 0; i < 1000_0000; i++) {
boolean b = map.containsKey(i + 1L);
}
long end = System.currentTimeMillis();
System.out.println("1000w元素 map耗时:" + (end-start));
List<Long> list = new ArrayList<>();
for (int i = 0; i < 10_0000; i++) {
list.add(i+1L);
}
long start2 = System.currentTimeMillis();
for (int i = 0; i < 10_0000; i++) {
boolean b = list.contains(i + 1L);
}
long end2 = System.currentTimeMillis();
System.out.println("10W元素 list耗时:" + (end2-start2));
Set<Long> set = new HashSet<>();
for (int i = 0; i < 1000_0000; i++) {
set.add(i+1L);
}
long start3 = System.currentTimeMillis();
for (int i = 0; i < 1000_0000; i++) {
boolean b = set.contains(i + 1L);
}
long end3 = System.currentTimeMillis();
System.out.println("1000w元素 set耗时:" + (end3-start3));
}
in conclusion:
The difference between map and set is not big
because of the hash table used in the bottom layer; because I only store a Long type id,
the list speed when I choose Set 1000w elements is too slow, goodbye!
Recommend key, value to choose HashMap;
I found a picture online:
Connect here: (Respect the original)
https://blog.csdn.net/high2011/article/details/106742629