Java集合-Set源码

绝地灬酷狼 2022-05-17 23:07 177阅读 0赞

## 简介 ##

> Set集合不包含重复的元素，相同的元素只保存一个，不包含相等的两个元素，Set至多只能包含一个NULL元素。Set的实现类都是基于Map来实现的，其中HashSet是通过HashMap来实现的，TreeSet是通过TreeMap实现的。

## 类图 ##

![这里写图片描述][70]

## 遍历方式 ##

public static void main(String[] args) { Set<String> set = new HashSet<>(); set.add("Lions are the most mighty of all animals in Africa."); set.add("Those kids always have so much enthusiasm about studying."); set.add("Calligraphy is the art of beautiful handwriting."); // 迭代器 Iterator<String> iterator = set.iterator(); while (iterator.hasNext()) { System.out.println(iterator.next()); } System.out.println("-------------------------------------------"); // 迭代器for循环 for (iterator = set.iterator();iterator.hasNext();){ System.out.println(iterator.next()); } System.out.println("-------------------------------------------"); // 加强型for循环 for (String str : set) { System.out.println(str); } }

## 源码 ##

> 参照JDK1.8版本

### Query Operations ###

//返回集合的大小 int size(); //集合为空，返回true，否则，返回false boolean isEmpty(); //判断集合是否包含指定对象o boolean contains(Object o); //返回set集合的迭代器 Iterator<E> iterator(); //Returns an array containing all of the elements in this set. Object[] toArray(); //Returns an array containing all of the elements in this set; <T> T[] toArray(T[] a);

### Modification Operations ###

//添加一个元素 boolean add(E e); //删除一个元素 boolean remove(Object o);

### Bulk Operations ###

//Returns true if this set contains all of the elements of the //specified collection. boolean containsAll(Collection<?> c); //将指定集合的全部元素添加到当前集合中 boolean addAll(Collection<? extends E> c); /** * In other words, removes from this set all of its elements * that are not contained in the specified collection. **/ boolean retainAll(Collection<?> c); /** * Removes from this set all of its elements that are contained * in the specified collection (optional operation). */ boolean removeAll(Collection<?> c); /** * Removes all of the elements from this set (optional operation). */ void clear();

### Comparison and hashing ###

//判断是否相等 boolean equals(Object o); //Returns the hash code value for this set. int hashCode();

[70]: /images/20220518/196fa23ae0c94e36be13514dffd8bcbf.png