Truncate a list to a given number of elements

list.subList(100, list.size()).clear();

or:

list.subList(0, 100);

Use List.subList:

import java.util.*;
import static java.lang.Math.min;

public class T {
  public static void main( String args[] ) {
    List<String> items = Arrays.asList("1");
    List<String> subItems = items.subList(0, min(items.size(), 2));

    // Output: [1]
    System.out.println( subItems );

    items = Arrays.asList("1", "2", "3");
    subItems = items.subList(0, min(items.size(), 2));

    // Output: [1, 2]
    System.out.println( subItems );
  }
}

You should bear in mind that subList returns a view of the items, so if you want the rest of the list to be eligible for garbage collection, you should copy the items you want to a new List:

List<String> subItems = new ArrayList<String>(items.subList(0, 2));

If the list is shorter than the specified size, expect an out of bounds exception. Choose the minimum value of the desired size and the current size of the list as the ending index.

Lastly, note that the second argument should be one more than the last desired index.