import java.util.*; 
class SetExample {
    public static void main (String[] args) {
	TreeSet t = new TreeSet();
	t.add("def");	t.add("abc");	t.add("ghi");
	// next statement prints [abc, def, ghi]
	System.out.println(t);

	// next statement prints "true"
	System.out.println(t.contains("def"));

	// remove "def" from the set t
	t.remove("def");

	// next statement prints "false"
	System.out.println(t.contains("def")); 
    }
}