for-each循环没有神奇的对象构造.这个语法：

for(Object o : Objects)

{

for(Object p : Objects2)

{

}

}

这只是简写：

for(Iterator iter = Objects.iterator(); iter.hasNext();)

{

Object o = iter.next();

for(Iterator iter2 = Objects2.iterator(); iter2.hasNext();)

{

Object p = iter2.next();

}

}

If would there be an iter2 reference created for every object I had in Objects?

这取决于Objects2的来源.它来自o吗？它还取决于Objects2.iterator()的实现方式. Iterable#iterator()应该返回独立的迭代器,这意味着Objects2.iterator()几乎肯定会为每次调用返回一个新的Iterator.但是,这并没有说明是否迭代Objects2中的对象(使用iter2)会创建其他新对象.

总的来说,这听起来像是过早的优化.

Which would create less Garbage Collection work?

都不是.增强的for循环(又名for-each循环)只是语法糖.编译器生成的字节码是相同的. Complete example:

package com.stackoverflow;

import java.util.Iterator;

public class Question14640184

{

public void enhancedForLoop(Iterable objects1, Iterable objects2)

{

for(Object o1 : objects1)

{

for(Object o2 : objects2)

{

// do something

}

}

}

public void iteratorForLoop(Iterable objects1, Iterable objects2)

{

for(Iterator iter1 = objects1.iterator(); iter1.hasNext();)

{

Object o1 = iter1.next();

for(Iterator iter2 = objects2.iterator(); iter2.hasNext();)

{

Object o2 = iter2.next();

}

}

}

}

编译：

✗ javac Question14640184.java

✗ javap -c Question14640184

Compiled from "Question14640184.java"

public class com.stackoverflow.Question14640184 extends java.lang.Object{

public com.stackoverflow.Question14640184();

Code:

0: aload_0

1: invokespecial #1; //Method java/lang/Object."":()V

4: return

public void enhancedForLoop(java.lang.Iterable, java.lang.Iterable);

Code:

0: aload_1

1: invokeinterface #2, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator;

6: astore_3

7: aload_3

8: invokeinterface #3, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z

13: ifeq 57

16: aload_3

17: invokeinterface #4, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;

22: astore 4

24: aload_2

25: invokeinterface #2, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator;

30: astore 5

32: aload 5

34: invokeinterface #3, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z

39: ifeq 54

42: aload 5

44: invokeinterface #4, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;

49: astore 6

51: goto 32

54: goto 7

57: return

public void iteratorForLoop(java.lang.Iterable, java.lang.Iterable);

Code:

0: aload_1

1: invokeinterface #2, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator;

6: astore_3

7: aload_3

8: invokeinterface #3, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z

13: ifeq 57

16: aload_3

17: invokeinterface #4, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object;

22: astore 4

24: aload_2

25: invokeinterface #2, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator;

30: astore 5

32: aload 5

34: invokeinterface #3, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z

39:

就像我说的那样,for-each循环只有syntactic sugar.

it’s something I’m just fixated on.

继续,朋友.