1·The key thing about both of them is that they were immutable.
关于他们有一点很关键的,就是他们都是不可变的。
2·When considering a tree of nodes where each node is an immutable data structure, we must consider how to modify a node or nodes inside the tree without modifying the entire tree.
在考虑每个节点都是一个不可变数据结构的节点树时，我们必须考虑如何修改树内的一个节点或多个节点，而不必更改整个树。
3·This pattern requires that the value being published be effectively immutable — that its state not change after publication.
这个模式要求被发布的值是有效不可变的——即值的状态在发布后不会更改。
4·If you have an immutable object, you must set whatever state it will contain in the constructor.
如果您有一个不可变对象，则必须要在构造函数中设置该对象将包含的任何状态。
5·Accessors for immutable properties will always have value semantics and do not need the defensive copying on either side of the call, making them more efficient.
不可变属性的存取器将总是具有值引用，因而调用的任何一方都不需要防御性复制，这使得它们效率更高。