hashset的contains什么作用 java 中 java hashset原理 文章目录 HashSet 简介 一、实现原理 二、源码分析 2.1 继承与实现关系 2.2 重要成员信息 2.3 构造方法 2.4 重要方法 2.4.1 添加 2.4.2 删除 三、对应线程安全实现 3.1 Collections 同步方法 3.2 CopyOnWriteArraySet HashSet 简介 HashSet是一个没有重复元素的...
HashSet 是无序无重复存储的，你new了两个Foo对象，但是值相同，HashSet里只会存一个，第二个new的Foo对象并没有存进去，contains（）是根据equals()和hashCode（）判断2个对象是否是同一个，你没重写hashCode（），系统默认按照地址计算hashCode，2个地址不同，hashCode也不同，返回当然是false。加上p...
To check whether an item exists in a HashSet, use the contains() method:Example cars.contains("Mazda"); Try it Yourself » Remove an ItemTo remove an item, use the remove() method:Example cars.remove("Volvo"); Try it Yourself » To remove all items, use the clear() method:...
首先我们现看Arraylist中contains方法里面有用到equals方法的地方: intindexOfRange(Object o,intstart,intend){//o为传进来要比较的元素或自定义对象,start为0,end为Arraylist元素个数Object[] es = elementData;if(o ==null) {//不为空不进入for(inti=start; i < end; i++) {if(es[i] ==null) {re...
对单个字符使用 string.Contains(char) 而不是 string.Contains(string)LeetCode 0217 - Contains ...
Returnstrueif this set contains no elements. Iterator<E>iterator() Returns an iterator over the elements in this set. booleanremove(Objecto) Removes the specified element from this set if it is present. intsize() Returns the number of elements in this set (its cardinality). ...
具体来说,是JDK7与JDK8的java.util.HashMap的hash算法以及HashMap的数据布局发生了变化。题主插入HashSet的是Integer,其hashCode()实现就返回int值本身。所以在对象hashCode这一步引入了巧合的“按大小排序”。然后HashMap.hash(Object)获取了对象的hashCode()之后会尝试进一步混淆。JDK8版java.util.HashMap内的hash...
Method Summary All MethodsInstance MethodsConcrete Methods Modifier and TypeMethodDescription Spliterator<E>spliterator() Creates alate-bindingandfail-fastSpliteratorover the elements in this set. Methods inherited from class java.util.HashSet add,clear,clone,contains,isEmpty,iterator,remove,size ...
() method are fail-fast: it will throw a ConcurrentModificationException if the set is modified after the creation of the iterator and by any method except through the iterator's remove() method. Notice that the fail-fast behavior cannot be guaranteed because nothing can be guaranteed in the...
The iterators returned by this class'siteratormethod arefail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's ownremovemethod, the Iterator throws aConcurrentModificationException. Thus, in the face of concurrent modification, the ...