LinkedHashSet

LinkedHashSet是HashSet的子类，底层使用hash算法计算存储位置，同时使用链表来维护顺序，顺序与添加顺序一致。在查看检索时，效率比较高。

底层数据结构是链表和哈希表。 1.由链表保证元素有序 2.由哈希表保证元素唯一

API方法实例

spliterator

@Test
public void spliterator() {
    //spliterator: 用于对集合数据的分割与遍历
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("spliterator method");
    Spliterator<Object> spliterator = linkedHashSet.spliterator();
    spliterator.forEachRemaining(System.out :: println);
}

add

@Test
public void add() {
    //add: 添加一条数据，不能重复
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("add");
    linkedHashSet.add("add");
    System.out.println("linkedHashSet = " + linkedHashSet);
}

clear

@Test
public void clear() {
    //clear:清除集合所有元素
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("clear");
    linkedHashSet.clear();
}

clone

@Test
public void Clone() {
    //clone: 复制打印集合所有元素
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("clone");
    System.out.println("linkedHashSet.clone() = " + linkedHashSet.clone());
}

contains

@Test
public void contains() {
    //contains: 判断集合是否存在指定元素，存在返回true，否则false
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("contains");
    System.out.println(linkedHashSet.contains("contains"));
}

isEmpty

@Test
public void isEmpty() {
    //isEmpty: 判断集合是否为空，空则返回true，否则false
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    //没有添加数据，返回为true
    System.out.println("linkedHashSet.isEmpty() = " + linkedHashSet.isEmpty());
}

iterator

@Test
public void iterator() {
    //iterator: 返回一个迭代器接口，用于遍历集合
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("iterator");
    Iterator<Object> iterator = linkedHashSet.iterator();
    iterator.forEachRemaining(System.out :: println);
}

remove

@Test
public void remove() {
    //remove: 移除集合指定元素
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("remove");
    //添加要移除的值
    linkedHashSet.remove("remove");
}

size

@Test
public void size() {
    //size: 返回集合长度
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    //集合没有数据，返回为0
    System.out.println("linkedHashSet.size() = " + linkedHashSet.size());
}

addAll

@Test
public void addAll() {
    //addAll: 根据Collection集合批量添加数据
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    Collection<Object> collection = new HashSet<>();
    collection.add("addAll");
    collection.add("addAll");
    //返回为true
    System.out.println(linkedHashSet.addAll(collection));
}

containsAll

@Test
public void containsAll() {
    //containsAll: 根据Collection集合比较set判断内容
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("containsAll");
    Collection<Object> collection = new LinkedHashSet<>();
    //添加匹配set集合的值
    collection.add("containsAll");
    //Collection里的值和set集合的值一直，所以判断为true
    System.out.println(linkedHashSet.containsAll(collection));
}

parallelStream

@Test
public void parallelStream() {
    //parallelStream: 返回一个顺序流方法
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("parallelStream");
    Stream<Object> parallelStream = linkedHashSet.parallelStream()
    //调用Stream接口方法遍历集合
    parallelStream.forEach(System.out::println);
}

stream

@Test
public void stream() {
    //stream: 返回一个stream流接口，可对集合进行操作
    LinkedHashSet<Object> linkedHashSet = new LinkedHashSet<>();
    linkedHashSet.add("stream");
    Stream<Object> stream = linkedHashSet.stream();
    //调用Stream接口方法判断集合总数
    System.out.println("stream.count() = " + stream.count());
}