TreeMap还是HashMap更快？
TreeMap还是HashMap更快？
本问题已经有答案：:
我正在编写一个字典，它在Map <String，Index> 中大量使用String作为键。我的关注点是在地图中搜索键的 HashMap 和 TreeMap 哪一个会导致更好（更快）的性能？
admin 更改状态以发布 2023年5月20日
public class MapsInvestigation {
public static HashMap hashMap = new HashMap();
public static TreeMap treeMap = new TreeMap();
public static ArrayList list = new ArrayList();
static {
for (int i = 0; i < 10000; i++) {
list.add(Integer.toString(i, 16));
}
}
public static void main(String[] args) {
System.out.println("Warmup populate");
for (int i = 0; i < 1000; i++) {
populateSet(hashMap);
populateSet(treeMap);
}
measureTimeToPopulate(hashMap, "HashMap", 1000);
measureTimeToPopulate(treeMap, "TreeMap", 1000);
System.out.println("Warmup get");
for (int i = 0; i < 1000; i++) {
get(hashMap);
get(treeMap);
}
measureTimeToContains(hashMap, "HashMap", 1000);
measureTimeToContains(treeMap, "TreeMap", 1000);
}
private static void get(Map map) {
for (String s : list) {
map.get(s);
}
}
private static void populateSet(Map map) {
map.clear();
for (String s : list) {
map.put(s, s);
}
}
private static void measureTimeToPopulate(Map map, String setName, int reps) {
long start = System.currentTimeMillis();
for (int i = 0; i < reps; i++) {
populateSet(map);
}
long finish = System.currentTimeMillis();
System.out.println("Time to populate " + (reps * map.size()) + " entries in a " + setName + ": " + (finish - start));
}
private static void measureTimeToContains(Map map, String setName, int reps) {
long start = System.currentTimeMillis();
for (int i = 0; i < reps; i++) {
get(map);
}
long finish = System.currentTimeMillis();
System.out.println("Time to get() " + (reps * map.size()) + " entries in a " + setName + ": " + (finish - start));
}
}
得到以下结果：
Warmup populate Time to populate 10000000 entries in a HashMap: 230 Time to populate 10000000 entries in a TreeMap: 1995 Warmup get Time to get() 10000000 entries in a HashMap: 140 Time to get() 10000000 entries in a TreeMap: 1164
