How do I randomly insert nodes into a binary search tree?

I'm a student learning about data structures in Java. I'm less than a beginner so please don't criticize my code too hardly :).

I want to randomly insert nodes into a binary search tree, but don't know how to do this if not manually.

I'll paste the Insert() method here and how I was previously inserting. Also I'm getting a compilation error because of the scanner. Any idea why?

	{
// Create node
Node node = new Node(key, data);
// Walk down the tree 
Node parent = null;
Node child = root;
while (child != null)
{
// Parent goes down
parent = child;
// Child goes down
if (key.compareTo(child.GetKey()) == 0)
throw new RuntimeException("Duplicate key.");
else if (key.compareTo(child.GetKey()) < 0)
child = child.left;
else
child = child.right;		
}
// Hang new node from parent or make it the root
node.parent = parent;
if (parent == null)
root = node;
else if (key.compareTo(parent.GetKey()) < 0)
parent.left = node;
else
parent.right = node;
}
import java.util.Scanner;
class Test
{
public static void main(String args[])
{
Tree tree = new Tree();
// Create keys
Node n1 = new Node(null, "1");
Node n2 = new Node(null, "2");
Node n3 = new Node(null, "3");
Node n4 = new Node(null, "4");
Node n5 = new Node(null, "5");
Node n6 = new Node(null, "6");
Node n7 = new Node(null, "7");
// Create Scanner
Scanner scanner = new Scanner();
System.out.print("Enter 'sorted' or 'random': ");
String s = scanner.nextLine();
if (s == "sorted")
tree.Insert("1", n1.GetData());
tree.Insert("2", n2.GetData());
tree.Insert("3", n3.GetData());
tree.Insert("4", n4.GetData());
tree.Insert("5", n5.GetData());
tree.Insert("6", n6.GetData());
tree.Insert("7", n7.GetData());
if (s == "random")
tree.Insert("5", n5.GetData());
tree.Insert("2", n2.GetData());
tree.Insert("1", n1.GetData());
tree.Insert("3", n3.GetData());
tree.Insert("6", n6.GetData());
tree.Insert("7", n7.GetData());
tree.Insert("4", n4.GetData());
if (s != "random" && s != "sorted")
throw new RuntimeException("Invalid input.");
}
}
</details>
# 答案1
**得分**: 0
以下是翻译好的内容：
在`Collections`类中有一个标准库方法可以对列表进行随机排序。要使用它，我们必须创建一个包含数据的列表，然后调用`Collections.shuffle`方法：
```java
List<String> data = new ArrayList();
for (int i = 1; i <= 7; i++) {
data.add(String.valueOf(i));
}
Collections.shuffle(data);

现在您可以将数据插入到树中：

for (String item: data) {
    tree.Insert(item, item);
}

关于编译错误，没有一个不带参数的Scanner构造函数。您可能想要传入系统的标准输入流。

// 创建Scanner
Scanner scanner = new Scanner(System.in);

我还注意到另一件事：您不能使用==来比较字符串，比如if (s == "sorted")，您必须使用equals方法：if (s.equals("sorted"))。

还有一件事，您需要在if语句中使用大括号{ }。否则，您希望有条件地运行的内容将始终运行。

if (s.equals("sorted")) {
    tree.Insert("1", n1.GetData());
    tree.Insert("2", n2.GetData()); // <-- 无论s是什么都会运行
}

List<String> data = new ArrayList();
for (int i = 1; i <= 7; i++) {
data.add(String.valueOf(i));
}
Collections.shuffle(data);

for (String item: data) {
tree.Insert(item, item);
}

    // Create Scanner
Scanner scanner = new Scanner(System.in);

    if (s == "sorted")
tree.Insert("1", n1.GetData());
tree.Insert("2", n2.GetData()); // <-- runs no matter what s is