public class SetUtil extends Object
| Constructor and Description |
|---|
SetUtil() |
| Modifier and Type | Method and Description |
|---|---|
static <E> Set<E> |
differenceView(Set<E> set1,
Set<?> set2)
set1, set2的差集(在set1,不在set2中的对象)的只读view,不复制产生新的Set对象.
|
static <E> Set<E> |
disjointView(Set<? extends E> set1,
Set<? extends E> set2)
set1, set2的补集(在set1或set2中,但不在交集中的对象,又叫反交集)的只读view,不复制产生新的Set对象.
|
static <T> Set<T> |
emptySet()
返回一个空的结构特殊的Set,节约空间.
|
static <T> Set<T> |
emptySetIfNull(Set<T> set)
如果set为null,转化为一个安全的空Set.
|
static <E> Set<E> |
intersectionView(Set<E> set1,
Set<?> set2)
set1, set2的交集(同时在set1和set2的对象)的只读view,不复制产生新的Set对象.
|
static <T> ConcurrentHashSet<T> |
newConcurrentHashSet()
根据等号左边的类型,构造类型正确的ConcurrentHashSet
|
static <T> HashSet<T> |
newHashSet()
根据等号左边的类型,构造类型正确的HashSet.
|
static <T> HashSet<T> |
newHashSet(Iterable<? extends T> elements)
HashSet涉及HashMap大小,因此建议在构造时传入需要初始的集合,其他如TreeSet不需要.
|
static <T> HashSet<T> |
newHashSet(T... elements)
根据等号左边的类型,构造类型正确的HashSet, 并初始化元素.
|
static <T> HashSet<T> |
newHashSetWithCapacity(int expectedSize)
创建HashSet并设置初始大小,因为HashSet内部是HashMap,会计算LoadFactor后的真实大小.
|
static <T> Set<T> |
newSetFromMap(Map<T,Boolean> map)
从Map构造Set的大杀器, 可以用来制造各种Set
|
static <T extends Comparable> |
newSortedSet()
根据等号左边的类型,构造类型正确的TreeSet, 通过实现了Comparable的元素自身进行排序.
|
static <T> TreeSet<T> |
newSortedSet(Comparator<? super T> comparator)
根据等号左边的类型,构造类型正确的TreeSet, 并设置comparator.
|
static <T> Set<T> |
singletonSet(T o)
返回只含一个元素但结构特殊的Set,节约空间.
|
static <E> Set<E> |
unionView(Set<? extends E> set1,
Set<? extends E> set2)
set1, set2的并集(在set1或set2的对象)的只读view,不复制产生新的Set对象.
|
static <T> Set<T> |
unmodifiableSet(Set<? extends T> s)
返回包装后不可修改的Set.
|
public static <T> HashSet<T> newHashSet()
Sets.newHashSet()public static <T> HashSet<T> newHashSet(T... elements)
Sets.newHashSet(Object...)public static <T> HashSet<T> newHashSet(Iterable<? extends T> elements)
Sets.newHashSet(Iterable)public static <T> HashSet<T> newHashSetWithCapacity(int expectedSize)
Sets.newHashSetWithExpectedSize(int)public static <T extends Comparable> TreeSet<T> newSortedSet()
Sets.newTreeSet()public static <T> TreeSet<T> newSortedSet(Comparator<? super T> comparator)
Sets.newTreeSet(Comparator)public static <T> ConcurrentHashSet<T> newConcurrentHashSet()
public static final <T> Set<T> emptySet()
Collections.emptySet()public static <T> Set<T> emptySetIfNull(Set<T> set)
Collections.emptySet()public static final <T> Set<T> singletonSet(T o)
Collections.singleton(Object)public static <T> Set<T> unmodifiableSet(Set<? extends T> s)
Collections.unmodifiableSet(Set)public static <T> Set<T> newSetFromMap(Map<T,Boolean> map)
Collections.newSetFromMap(Map)public static <E> Set<E> unionView(Set<? extends E> set1, Set<? extends E> set2)
public static <E> Set<E> intersectionView(Set<E> set1, Set<?> set2)
public static <E> Set<E> differenceView(Set<E> set1, Set<?> set2)
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