CODEWITHSUNDEEP
javafor-loopforeach
user1875195
user1875195

Reputation: 988

nested foreach statement in java

Is it possible to nest foreach statements in java and start the nested statement at the current index that the outer foreach loop is at?

So if I have 

List<myObj> myObjList = new ArrayList<myObj>();

for (myObj o : myObjList){
    // how do I start the nested for loop at the current spot in the list?
    for(

}

Thanks!

Upvotes: 3

Views: 13813

Answers (3)

Tim S.
Tim S.

Reputation: 56586

Here's a way to do it by keeping track of the index yourself, then using subList to start the inner loop at the right spot:

int i = 0;
for (myObj o1 : myObjList) {
    for (myObj o2 : myObjList.subList(i, myObjList.size())) {
        // do something
    }
    i++;
}

I think this is clearer than using basic for loops, but that's certainly debatable. However, both should work, so the choice is yours. Note that if you are using a collection that does not implement List<E>, this will not work (subList is defined on List<E> as the idea of an "index" really only makes sense for lists).

Upvotes: 6

Reimeus
Reimeus

Reputation: 159874

No. Enhanced for loops conceal the current index of the loop. You need to use a basic for loop which uses an index.

Upvotes: 6

Richard Sitze
Richard Sitze

Reputation: 8463

While you could do something like this, it would be extremely sub-optimal. Consider that the indexOf method would be iterating across the entire list (again!) to find the object. Note also that it depends on myObjList being an ordered collection (list):

List<myObj> myObjList = new ArrayList<myObj>();

for (myObj o : myObjList){
    int idx = myObjList.indexOf(o);
    for(myObj blah : myObjList.subList(idx, myObjList.size()) {
        ...
    }

}

far better:

int myObjListSize = myObjList.size();
for (int outerIndex = 0; outerIndex < myObjListSize ; outerIndex++){
    for(int innerIndex = outerIndex; innerIndex < myObjListSize ; innerIndex++) {
        myObj o = myObjList.get(innerIndex);
    }

}

other note: class myObj should be capitalized to class MyObj to adhere to Java naming standards

Upvotes: 1

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