Java doesn't enforce the rule "mutable XOR shared". But if you have a link "child" in the parent node, and a link "parent" in the child node, then parent.child.

Java doesn't enforce the rule "mutable XOR shared". But if you have a link "child" in the parent node, and a link "parent" in the child node, then parent.child.parent == parent, and compiler cannot know it. So Rust as the language makes it impossible to do with &-pointers, while standard library of Rust allows it to do with combination of Option, Rc, RefCell but it is really ugly (people above says it is impossible, but I believe it is just ugly in all ways). Like this: type NodeRef = Rc<RefCell<NodeInner>>; struct Node { parent: Option<NodeRef>, left: Option<NodeRef>, right: Option<NodeRef> } So the real type of `parent` field is Option<Rc<RefCell<NodeInner>>>. I hate it when it comes to that. But the ugliness is not the only issue. Now any attempt to access parent or child node will go through 2 runtime checks: Option need to check that there is Some reference or just None, and RefCell needs to check that the invariant mut^shared will not be broken. And all this checks must be handled, so your code will probably have a lot of unwraps or ? which worsens the ugliness problem. And yeah, with Rc you need to watch for memory leaks. You need to break all cycles before you allow destructors to run. If I need to write a tree in rust, I'll use raw-pointers and unsafe, and let allergic to unsafe rustaceans say what they like, I just don't care.