How to delete elements in a Java collection

Often we want to delete some elements in the collection.　　Some might write that. public void operate (List list) {for (Iterator it = List.iterator (); It.hasnext ();)　　{String str = (string) it.next ();　　if (Str.equals ("Chengang")) {list.remove (str); This writing is run with the following exception: Exception in thread ' main ' java.util.ConcurrentModificationException at java.util.abstractlist$ Itr.checkforcomodification (abstractlist.java:449) because the list cannot delete its elements while it is in the loop. Then I did it, a very stupid way, the idea is this: Create a list of the elements to be deleted specifically, after the loop, with the List.removeall method to remove the elements.　　The code is as follows: public void operate (List list) {list removelist= new ArrayList (); for (Iterator it = List.iterator (); It.hasnext ();)　　{String str = (string) it.next ();　　if (Str.equals ("Chengang")) {Removelist.add (str);　　} list.removeall (Removelist); This can also solve the problem, but the method is too cumbersome, in fact, there can be a simpler and more efficient way, is to use the Iterator.remove method, as follows: for (iterator it = List.iterator (); It.hasnext ();)　　{String str = (string) it.next ();　　if (Str.equals ("Chengang")) {it.remove (); So, the more you know about the basics of Java, the more concise your code will be. Conversely, if your code is particularly complex, there must be a problem with the method or design.