第194題

Given:
enum Example{ONE, TWO, THREE}
Which statement is true?
A. The expressions (ONE == ONE) and ONE.equals(ONE) are both guaranteed to be true.
B. The expression (ONE < TWO) is guaranteed to be true and ONE.compareTo(TWO) is guaranteed to be
less than one.
C. The Example values cannot be used in a raw javautil.HashMap; instead, the programmer must use a
java.util.EnumMap.
D. The Example values can be used in a java.util.SortedSet, but the set will NOT be sorted because
enumerated types do NOT implement java.lang.Comparable.

答案：A
參考：8-6 Java列舉類型、12-4-3 SortedSet集合、12-5-1 HashMap