Discussion
What will be the output of the program?
import java.util.*;
public class Demo49
{
public static void main(String[] args)
{
List<String> l = new ArrayList<String>(
Arrays.asList("a", "b", "c"));
List<String> view = l.subList(0, 2);
view.set(0, "z");
System.out.println(l);
}
}
Answer: A
Correct answer: The program prints [z, b, c]
subList returns a *view* onto the backing list, not a copy, so writing through the view writes through to the original: setting index 0 of the view sets index 0 of the list. Printing l therefore shows [z, b, c] - the whole list, with only the first element changed. The view is also fragile: structurally modifying the backing list through any other route invalidates it.
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