1、Queue声明创建对象。(Queue为泛型对象。)
public class Queue<T> :IEnumerable<T>,System.Collections.ICollection,IReadOnlyCollection<T>
本质为Array对象存储数据。
Queue<string> qy = new Queue<string>(); private T[] _array public Queue() { _array = Array.Empty<T>(); } Queue<int> qy1 = new Queue<int>(12); public Queue(int capacity) { if (capacity < 0) throw new ArgumentOutOfRangeException(nameof(capacity), capacity, SR.ArgumentOutOfRange_NeedNonNegNum); _array = new T[capacity]; }
Queue<int> qy2 = new Queue<int>(new List<int>()); public Queue(IEnumerable<T> collection) { if (collection == null) throw new ArgumentNullException(nameof(collection)); _array = EnumerableHelpers.ToArray(collection, out _size); if (_size != _array.Length) _tail = _size; }
2、队列的空间是实际存储值的两倍，如果小于两倍则每次增场4的长度。
1 if (_size == _array.Length) 2 { 3 int newcapacity = (int)((long)_array.Length * (long)GrowFactor / 100); 4 if (newcapacity < _array.Length + MinimumGrow) 5 { 6 newcapacity = _array.Length + MinimumGrow; 7 } 8 SetCapacity(newcapacity); 9 }
3、Queue为先进先出。
进队列在数组末尾赋值
public void Enqueue(T item) { if (_size == _array.Length) { int newcapacity = (int)((long)_array.Length * (long)GrowFactor / 100); if (newcapacity < _array.Length + MinimumGrow) { newcapacity = _array.Length + MinimumGrow; } SetCapacity(newcapacity); } _array[_tail] = item; MoveNext(ref _tail); _size++; _version++; }
出队列则从头部取值
public T Dequeue() { int head = _head; T[] array = _array; if (_size == 0) { ThrowForEmptyQueue(); } T removed = array[head]; if (RuntimeHelpers.IsReferenceOrContainsReferences<T>()) { array[head] = default!; } MoveNext(ref _head); _size--; _version++; return removed; }
4、TryDequeue 与 Dequeue()区别在于 TryDequeue 判断size为0时，返回false 并out 泛型的默认值
public bool TryDequeue([MaybeNullWhen(false)] out T result) { int head = _head; T[] array = _array; if (_size == 0) { result = default!; return false; } result = array[head]; if (RuntimeHelpers.IsReferenceOrContainsReferences<T>()) { array[head] = default!; } MoveNext(ref _head); _size--; _version++; return true; }
注：MaybeNullWhenAttribute(Boolean) 返回值条件。 如果方法返回此值，则关联的参数可能为 null
5、Peek 仅仅时查看一下下一个要返回的值，不从数组移除
if (_size == 0) { result = default!; return false; } result = _array[_head]; return true;
随是拙见，但为原创，转载注明出处，敬谢
Queue 常用的方法大约就这些。先写道这里，碎觉。
以下为公众号，一起学起来~
原文：https://www.cnblogs.com/xtt321/p/12293473.html