按说HashMap的负载极限为0.75，可是，测试程序并看不出这个结果。待探讨
测试程序如下：
根据结果看不出来预定义有什么影响。
public class test {
public static void main(String[] args) {
testRun(5000000);
testRun(10000000);
testRun(15000000);
testRun(20000000);
testRun(25000000);
testRun(30000000);
testRun(35000000);
testRun(40000000);
testRun(45000000);
testRun(50000000);
}
public static void testRun(int mapCount){
System.out.println("============"+mapCount+"=============");
run(mapCount,new HashMap<>());
run(mapCount,new HashMap<>(mapCount));
run(mapCount,new HashMap<>((int)(mapCount/0.75)));
run(mapCount,new HashMap<>((int)(mapCount/0.6)));
run(mapCount,new HashMap<>((int)(mapCount/0.5)));
}
public static void run(int mapCount,Map<Integer,String> testMap){
String testValue = "";
Long startTime0 = System.currentTimeMillis();
for(int i = 1;i<mapCount;i++){
testMap.put(i, testValue);
}
Long endTime0 = System.currentTimeMillis();
System.out.println(endTime0-startTime0);
}
}
============5000000============= 1670 689 981 260 211 ============10000000============= 1097 4485 793 386 331 ============15000000============= 768 3394 2805 5651 6022 ============20000000============= 8155 2153 5089 6078 6809 ============25000000============= 8890 6998 10050 9149 10501 ============30000000============= 14467 10527 9334 11453 13733 ============35000000============= 14493 11978 13706 13809 11461 ============40000000============= 15788 13439 18142 13514 11351 ============45000000============= 12952 18501 17793 11894 30664 ============50000000============= 29528 14534 14272 32803 42236
时间： 2024-10-24 05:12:18