哈希映射与数组性能
2022-09-01 07:40:38
当数组的索引已知时,使用数组或哈希映射是否更好(性能方面)更好?请记住,示例中的“对象数组/映射”只是一个示例,在我的实际项目中,它是由另一个类生成的,因此我不能使用单个变量。
数组示例:
SomeObject[] objects = new SomeObject[2];
objects[0] = new SomeObject("Obj1");
objects[1] = new SomeObject("Obj2");
void doSomethingToObject(String Identifier){
SomeObject object;
if(Identifier.equals("Obj1")){
object=objects[0];
}else if(){
object=objects[1];
}
//do stuff
}
哈希映射示例:
HashMap objects = HashMap();
objects.put("Obj1",new SomeObject());
objects.put("Obj2",new SomeObject());
void doSomethingToObject(String Identifier){
SomeObject object = (SomeObject) objects.get(Identifier);
//do stuff
}
HashMap看起来好多了,但我真的需要性能,以便具有优先级。
编辑:好吧,阵列就是这样,建议仍然欢迎
编辑:我忘了提一下,数组/哈希映射的大小总是一样的(6)
编辑:看起来哈希映射更快 数组:128ms 哈希:103ms
当使用较少的周期时,HashMaps甚至快了一倍
测试代码:
import java.util.HashMap;
import java.util.Random;
public class Optimizationsest {
private static Random r = new Random();
private static HashMap<String,SomeObject> hm = new HashMap<String,SomeObject>();
private static SomeObject[] o = new SomeObject[6];
private static String[] Indentifiers = {"Obj1","Obj2","Obj3","Obj4","Obj5","Obj6"};
private static int t = 1000000;
public static void main(String[] args){
CreateHash();
CreateArray();
long loopTime = ProcessArray();
long hashTime = ProcessHash();
System.out.println("Array: " + loopTime + "ms");
System.out.println("Hash: " + hashTime + "ms");
}
public static void CreateHash(){
for(int i=0; i <= 5; i++){
hm.put("Obj"+(i+1), new SomeObject());
}
}
public static void CreateArray(){
for(int i=0; i <= 5; i++){
o[i]=new SomeObject();
}
}
public static long ProcessArray(){
StopWatch sw = new StopWatch();
sw.start();
for(int i = 1;i<=t;i++){
checkArray(Indentifiers[r.nextInt(6)]);
}
sw.stop();
return sw.getElapsedTime();
}
private static void checkArray(String Identifier) {
SomeObject object;
if(Identifier.equals("Obj1")){
object=o[0];
}else if(Identifier.equals("Obj2")){
object=o[1];
}else if(Identifier.equals("Obj3")){
object=o[2];
}else if(Identifier.equals("Obj4")){
object=o[3];
}else if(Identifier.equals("Obj5")){
object=o[4];
}else if(Identifier.equals("Obj6")){
object=o[5];
}else{
object = new SomeObject();
}
object.kill();
}
public static long ProcessHash(){
StopWatch sw = new StopWatch();
sw.start();
for(int i = 1;i<=t;i++){
checkHash(Indentifiers[r.nextInt(6)]);
}
sw.stop();
return sw.getElapsedTime();
}
private static void checkHash(String Identifier) {
SomeObject object = (SomeObject) hm.get(Identifier);
object.kill();
}
}