Java iterator.hasNext() is always true

问题:

I have a little problem with the code as seen below. The iterator().hasNext() will never turn into false because the next() function always returns the same element. It ends in an infinite loop.

I would like to set the attribute UserLock in every element in the collection (returned from GetElements()). If the type of the element is "Package", I will lock all elements under the package with a recursive call of the lockAllElements function.

private void lockAllElements(String internalGUID) {     Element tempElem = null;      while((repo.GetPackageByGuid(internalGUID).GetElements().iterator().hasNext()) == true) {         tempElem = repo.GetPackageByGuid(internalGUID).GetElements().iterator().next();          if(tempElem.GetType().equals("Package")) {                             this.lockAllElements(tempElem.GetElementGUID());         }          tempElem.ApplyUserLock();      } } 

回答1:

It is always true because you get a new Iterator instance in each iteration of your loop. You should get a single Iterator instance and use that instance throughout the loop.

Change

while((repo.GetPackageByGuid(internalGUID).GetElements().iterator().hasNext()) == true) {     tempElem = repo.GetPackageByGuid(internalGUID).GetElements().iterator().next();     ... 

to

Iterator<Element> iter = repo.GetPackageByGuid(internalGUID).GetElements().iterator(); while(iter.hasNext()) {     tempElem = iter.next();     ... 

回答2:

Following on from @Eran's answer... I sometimes prefer a for loop:

for (Iterator<Element> iter = repo.GetPackageByGuid(internalGUID).GetElements().iterator(); it.hasNext(); ) {     tempElem = iter.next(); } 

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