To determine the statements that are true, let's analyze the given code:
public static void before() {
Set set = new TreeSet();
set.add("2");
set.add(3);
set.add("1");
Iterator it = set.iterator();
while (it.hasNext()) System.out.print(it.next() + " ");
}
The code creates a TreeSet named set, which is a sorted set that does not allow duplicate elements. It then adds three elements to the set: the string "2", the integer 3, and the string "1".
The code then creates an iterator named it and iterates over the elements in the set using a while loop. Inside the loop, it prints each element followed by a space.
Based on the code logic and the behavior of TreeSet, let's evaluate each statement:
A. The before() method will print 1 2
This statement is incorrect. The TreeSet orders elements in ascending order. In this case, "1" will be printed before "2" because strings are ordered lexicographically. Therefore, the correct output would be "1 2 3", not "1 2".
B. The before() method will print 1 2 3
This statement is correct. As explained above, the TreeSet orders elements in ascending order, so the correct output would be "1 2 3".
C. The before() method will print three numbers, but the order cannot be determined
This statement is incorrect. The TreeSet orders elements in ascending order, so the order of the elements can be determined.
D. The before() method will not compile
This statement is incorrect. The code does not contain any compilation errors.
E. The before() method will throw an exception at runtime
This statement is correct. The code attempts to add elements of different types (a string and an integer) to the TreeSet. However, TreeSet requires the elements to be mutually comparable. Since the elements are not of the same type or mutually comparable, a ClassCastException will be thrown at runtime.
Therefore, the correct statements are:
B. The before() method will print 1 2 3
E. The before() method will throw an exception at runtime
The correct answer is E.