This example is about replacing a List element while ensuring that the replacement element is at the same position as the element that is replaced.
This can be done using these methods:
Consider an ArrayList containing the elements “Program starting!”, “Hello world!” and “Goodbye world!”
List<String> strings = new ArrayList<String>();
strings.add("Program starting!");
strings.add("Hello world!");
strings.add("Goodbye world!");If we know the index of the element we want to replace, we can simply use set as follows:
strings.set(1, "Hi world");If we don’t know the index, we can search for it first. For example:
int pos = strings.indexOf("Goodbye world!");
if (pos >= 0) {
strings.set(pos, "Goodbye cruel world!");
}Notes:
set operation will not cause a ConcurrentModificationException.
set operation is fast ( O(1) ) for ArrayList but slow ( O(N) ) for a LinkedList.
indexOf search on an ArrayList or LinkedList is slow ( O(N) ).