如何在Java中实现一个红黑树？

在Java中实现一个红黑树可以通过以下步骤：

1. 定义红黑树的节点结构，包括节点的值、颜色、父节点、左子节点和右子节点等属性。

enum Color {
    RED,
    BLACK
}

class Node {
    int val;
    Color color;
    Node parent;
    Node left;
    Node right;
    
    public Node(int val) {
        this.val = val;
        this.color = Color.RED; // 新插入的节点默认为红色
    }
}

2. 实现红黑树的插入操作，它要求按照红黑树的规则将新节点插入到正确的位置上，并通过旋转和变色操作来保持树的平衡。

class RedBlackTree {
    Node root;
    
    public void insert(int val) {
        Node node = new Node(val);
        Node parent = null;
        Node current = root;
        
        // 查找新节点的插入位置
        while (current != null) {
            parent = current;
            if (val < current.val) {
                current = current.left;
            } else {
                current = current.right;
            }
        }
        
        // 将新节点插入到树中
        node.parent = parent;
        if (parent == null) {
            root = node;
        } else if (val < parent.val) {
            parent.left = node;
        } else {
            parent.right = node;
        }
        
        // 调整树的平衡
        insertFixup(node);
    }
    
    private void insertFixup(Node node) {
        while (node.parent != null && node.parent.color == Color.RED) {
            // 父节点是祖父节点的左子节点
            if (node.parent == node.parent.parent.left) {
                Node uncle = node.parent.parent.right;
                if (uncle != null && uncle.color == Color.RED) {
                    // Case 1：叔叔节点是红色
                    node.parent.color = Color.BLACK;
                    uncle.color = Color.BLACK;
                    node.parent.parent.color = Color.RED;
                    node = node.parent.parent;
                } else {
                    // Case 2：叔叔节点是黑色，且当前节点是右子节点
                    if (node == node.parent.right) {
                        node = node.parent;
                        leftRotate(node);
                    }
                    // Case 3：叔叔节点是黑色，且当前节点是左子节点
                    node.parent.color = Color.BLACK;
                    node.parent.parent.color = Color.RED;
                    rightRotate(node.parent.parent);
                }
            } else {
                // 父节点是祖父节点的右子节点
                Node uncle = node.parent.parent.left;
                if (uncle != null && uncle.color == Color.RED) {
                    // Case 1：叔叔节点是红色
                    node.parent.color = Color.BLACK;
                    uncle.color = Color.BLACK;
                    node.parent.parent.color = Color.RED;
                    node = node.parent.parent;
                } else {
                    // Case 2：叔叔节点是黑色，且当前节点是左子节点
                    if (node == node.parent.left) {
                        node = node.parent;
                        rightRotate(node);
                    }
                    // Case 3：叔叔节点是黑色，且当前节点是右子节点
                    node.parent.color = Color.BLACK;
                    node.parent.parent.color = Color.RED;
                    leftRotate(node.parent.parent);
                }
            }
        }
        
        root.color = Color.BLACK;
    }
    
    private void leftRotate(Node node) {
        Node right = node.right;
        node.right = right.left;
        if (right.left != null) {
            right.left.parent = node;
        }
        right.parent = node.parent;
        if (node.parent == null) {
            root = right;
        } else if (node == node.parent.left) {
            node.parent.left = right;
        } else {
            node.parent.right = right;
        }
        right.left = node;
        node.parent = right;
    }
    
    private void rightRotate(Node node) {
        Node left = node.left;
        node.left = left.right;
        if (left.right != null) {
            left.right.parent = node;
        }
        left.parent = node.parent;
        if (node.parent == null) {
            root = left;
        } else if (node == node.parent.left) {
            node.parent.left = left;
        } else {
            node.parent.right = left;
        }
        left.right = node;
        node.parent = left;
    }
}

3. 实现红黑树的删除操作，它要求按照红黑树的规则删除指定的节点，并通过旋转和变色操作来保持树的平衡。

class RedBlackTree {
    ...
    
    public void delete(int val) {
        Node node = search(val);
        if (node == null) {
            return;
        }
        
        Node replace = null;
        Color originalColor = node.color;
        if (node.left == null) {
            replace = node.right;
            transplant(node, node.right);
        } else if (node.right == null) {
            replace = node.left;
            transplant(node, node.left);
        } else {
            Node min = minimum(node.right);
            replace = min.right;
            originalColor = min.color;
            if (min.parent == node) {
                replace.parent = min;
            } else {
                transplant(min, min.right);
                min.right = node.right;
                min.right.parent = min;
            }
            transplant(node, min);
            min.left = node.left;
            min.left.parent = min;
            min.color = node.color;
        }
        
        if (originalColor == Color.BLACK) {
            deleteFixup(replace);
        }
    }
    
    private void deleteFixup(Node node) {
        while (node != root && node.color == Color.BLACK) {
            if (node == node.parent.left) {
                Node sibling = node.parent.right;
                if (sibling.color == Color.RED) {
                    // Case 1：兄弟节点是红色
                    sibling.color = Color.BLACK;
                    node.parent.color = Color.RED;
                    leftRotate(node.parent);
                    sibling = node.parent.right;
                }
                if (sibling.left.color == Color.BLACK && sibling.right.color == Color.BLACK) {
                    // Case 2：兄弟节点和它的子节点都是黑色
                    sibling.color = Color.RED;
                    node = node.parent;
                } else {
                    if (sibling.right.color == Color.BLACK) {
                        // Case 3：兄弟节点是黑色，兄弟节点的左子节点是红色，右子节点是黑色
                        sibling.left.color = Color.BLACK;
                        sibling.color = Color.RED;
                        rightRotate(sibling);
                        sibling = node.parent.right;
                    }
                    // Case 4：兄弟节点是黑色，兄弟节点的右子节点是红色
                    sibling.color = node.parent.color;
                    node.parent.color = Color.BLACK;
                    sibling.right.color = Color.BLACK;
                    leftRotate(node.parent);
                    node = root;
                }
            } else {
                Node sibling = node.parent.left;
                if (sibling.color == Color.RED) {
                    // Case 1：兄弟节点是红色
                    sibling.color = Color.BLACK;
                    node.parent.color = Color.RED;
                    rightRotate(node.parent);
                    sibling = node.parent.left;
                }
                if (sibling.right.color == Color.BLACK && sibling.left.color == Color.BLACK) {
                    // Case 2：兄弟节点和它的子节点都是黑色
                    sibling.color = Color.RED;
                    node = node.parent;
                } else {
                    if (sibling.left.color == Color.BLACK) {
                        // Case 3：兄弟节点是黑色，兄弟节点的右子节点是红色，左子