16.10 Sets
A Set is an unordered Collection
of unique elements (i.e., no duplicates). The collections framework contains several Set
implementations, including HashSet and TreeSet. HashSet
stores its elements in a hash table, and TreeSet
stores its elements in a tree. Hash tables are presented in Section 16.11. Trees are discussed in Section 21.7.
Figure 16.16 uses a HashSet
to remove duplicate strings from a List
. Recall that both List
and Collection
are generic types, so line 16 creates a List
that contains String
objects, and line 20 passes a Collection
of String
s to method printNonDuplicates
. Method printNonDuplicates
(lines 24–35) takes a Collection
argument. Line 27 constructs a HashSet<String>
from the Collection<String>
argument. By ...
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