我自己去实验了。事实证明,使用 1000 个元素创建HashMap 的 ArrayList 的方法大约快 40 倍。
public class HashMapVsArrayOfHashMap {
public static void main(String[] args){
ArrayList<HashMap<String, String>> listOfMaps=new ArrayList<HashMap<String,String>>();
for( int i=0;i<1000;i++){
final int finalI=i;
listOfMaps.add(new HashMap<String, String>(){{put("asdfasdfasdfasdfadsf"+finalI,"asdfsdafasdfsadfasdf"+finalI);}});
}
LinkedHashMap<String, String> map=new LinkedHashMap<String, String>();
for(int i=0;i<1000;i++)
map.put("asdfasdfasdfasdfadsf"+i,"asdfsdafasdfsadfasdf"+i);
int position=700;
testArrayList("Method1:ArrayListOfHashMaps",position,listOfMaps);
testHashMap("Method2:LinkedHashMap",position,map);
}
private static void testArrayList(String string, int position,
ArrayList<HashMap<String, String>> listOfMaps) {
long start, end;
start=System.nanoTime();
listOfMaps.get(position).get("asdfasdfasdfasdfadsf"+position);
end=System.nanoTime();
System.out.println(string+"|Difference = "+(end-start));
}
private static void testHashMap(String string, int position,
LinkedHashMap<String, String> map) {
long start, end;
start=System.nanoTime();
String s= new ArrayList<String>(map.keySet()).get(position);
end=System.nanoTime();
System.out.println(string+"|Difference = "+(end-start));
}
}
当您将大小增加到 30,000 个元素时 - 差异是巨大的。