- o
- object to be checked for containment in this deque
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Type Reason Java.Lang.ClassCastException if the class of the specified element is incompatible with this deque (optional) Java.Lang.NullPointerException if the specified element is null (optional)
Returns true if this deque contains the specified element. More formally, returns true if and only if this deque contains at least one element e such that o.equals(e).