8/3/2019 ICS23q2fal11
2/2
4. (7 pts) AMapis an injection between keys and values when
every value has exactly one key that maps
to it. Or stated another way, a map is not aninjection if it has
two keys that map to the same value.
Complete the public static generic booleanmethod isInjection,
which takes a Mapand determines
whether or not it is an injection, according to either of the
criteria stated above.
Hint: Code this method by using a local variable that is
Set(using theArraySetimplementation) and looking
at every key and determining if its associated value has already
been seen as an association from a previously
examined key. An elegant (short/efficient) solution will get the
most credit.
public static boolean isInjection (Map m) {
5. (3 pts) Complete the public static generic method nthGet,
which takes a Mapmthat is a permutation
(every key in it maps to a value that is also a key in the Map),
a starting key k in the map, and a non-
negative integer nand returns the nthkey gotten from the map
starting with key k: ifnis 0return k; ifnis
1return m.get(k); ifnis 2return m.get(m.get(k)); ifnis 3return
m.get(m.get(m.get(k))); etc.: it
does ncalls to get. Assume (do NOT check) that mis a
permutation; but, throw an appropriate exception
ifkis not a key in m, or ifn< 0(which includes ks and ns
their actual values).
public static K nthGet (Map m, K k, int n) {
