RemoveAll inside for is not removing elements. When I checked with whe

Question

RemoveAll inside for is not removing elements. When I checked with where I get all the elements. This is weird,I thought foreach is immutable so I went with for and length of list.... anyone?

Rajanikant Hawaldar · Answer

Yes when you are looping a list removing an element, adding an element in that loop is illigal event

Sachin Singh · Answer

what do you mean by RemoveAll inside foreach? please give some code examples.

Pranam Bhat · Answer

It basically removes the element with the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))) (if such an element exists). Also, it might be your objects are not equal! just their number field. Override the equals method of your contacts class und use it to compare them. ArrayList#removeAll(Collection) uses List#remove(Object) which uses equals. Scenario: How are 2 members determined to be equal? I'm guessing if they have the same ID, you deem them equal, however java wants them to be the exact same reference in memory which may not be the case. To correct for this you can override the equals function to have it return if the ids are equal: public class Member { //.. @Override public boolean equals(Object anObject) { if (!(anObject instanceof Member)) { return false; } Member otherMember = (Member)anObject; return otherMember.getUserUID().equals(getUserUID()); } } Also when you override .equals it is recommended to also override hashCode so that the objects also work correctly in hashing functions like Set or Map.

Mallesh Mallu · Answer

@Raj OK, @sachin I am looping list using for loop and inside loop I am trying to remove items using loop index with same list

Mallesh Mallu · Answer

Yes i am using where and assigning the values to the same list and works for now but i am still wondering why RemoveAll was not working.

Rajanikant Hawaldar · Answer

You are trying remove all from the same list which you are looping?