An error is reported when traversing the list collection to delete elements

 

When traversing the list collection to delete elements, problems such as index out of bounds exception or incomplete content traversal will occur

Example:

List< String> al = new ArrayList< String>();

    al.add(“12”);

    al.add(“1”);

    al.add(“13”);  

    int size = al.size();

 

 

 

Problem 1: index out of bounds exception in thread “main” java.lang.indexoutofboundsexception: index: 2, size: 2

  for(int i=0; i< size; i++){

    if(“1”.equals(al.get(i)))

      al.remove(i);

   }

Problem analysis: delete an element after meeting the conditions. There are only two elements in the collection. Only al. Get (0) and al. Get (1) can be used. When al. Get (2) obtains elements, the index exceeds the limit. Some students may want to change the number of sizes above to al. Size (). Although the index crossing problem is solved, there is a problem of incomplete traversal

 

 

Problem 2: incomplete content traversal

for(int i=0; i< al.size(); i++){

    if(“1”.equals(al.get(i)))

      al.remove(i);

   }

Problem analysis: delete an element after meeting the conditions, and no longer cycle the third element

 

 

Correct code:

Iterator< String> it = al.iterator();

    while(it.hasNext()){

    if(“1”.equals(it.next()))

      it.remove();

   }