Java函数传参数

class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;

    public TreeNode() {
    }
public TreeNode(int val) {
        this.val = val;
    }
}

public class Solution {
    public static void main(String[] args) {
        TreeNode t1 = null;
        change(t1);
        System.out.println(t1==null?null:t1.val);

        TreeNode t2 = new TreeNode(100);
        Change(t2);
        System.out.println(t2.val);
    }

    //无论传递的参数是否是null，都无法在函数内部改变引用变量的指向！
    public static void change(TreeNode t1){
        t1 = new TreeNode(100);
    }

    public static void Change(TreeNode t2){

　　　　t1 = new TreeNode(200);

    } 

}