Цитата(Tony @ 11.9.2006, 16:32  ) | | Какой из циклов(while,for) будет бысстрей работать с коллекцией? Слышел 4то for. |
Абсолютно одинаково.
Возьмем такой класс:
| Код | import java.util.*;
public class Test
{
public void iter1()
{
List <String>list=new ArrayList<String>();
for(Iterator<String> it=list.iterator();it.hasNext();){
String string=it.next();
}
}
public void iter2()
{
List <String>list=new ArrayList<String>();
Iterator <String>it=list.iterator();
while(it.hasNext()){
String string=it.next();
}
}
} |
и дизассемблируем его:
| Код | Compiled from "Test.java"
public class Test extends java.lang.Object{
public Test();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
public void iter1();
Code:
0: new #2; //class java/util/ArrayList
3: dup
4: invokespecial #3; //Method java/util/ArrayList."<init>":()V
7: astore_1
8: aload_1
9: invokeinterface #4, 1; //InterfaceMethod java/util/List.iterator:()Ljava/util/Iterator;
14: astore_2
15: aload_2
16: invokeinterface #5, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z
21: ifeq 37
24: aload_2
25: invokeinterface #6, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
30: checkcast #7; //class java/lang/String
33: astore_3
34: goto 15
37: return
public void iter2();
Code:
0: new #2; //class java/util/ArrayList
3: dup
4: invokespecial #3; //Method java/util/ArrayList."<init>":()V
7: astore_1
8: aload_1
9: invokeinterface #4, 1; //InterfaceMethod java/util/List.iterator:()Ljava/util/Iterator;
14: astore_2
15: aload_2
16: invokeinterface #5, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z
21: ifeq 37
24: aload_2
25: invokeinterface #6, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;
30: checkcast #7; //class java/lang/String
33: astore_3
34: goto 15
37: return
} |
Как видишь байткод одинаковый.
|
