java的迭代器遍历问题

Question

package 案例;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Scanner;

class action {
    public static Scanner scanner = new Scanner(System.in);
    private String name;
    private String color;
    private String price;
    private String amount;
    public static Collection<action> collection = new ArrayList<action>();
    private int x;

    public action(String name, String color, String price, String amount) {
        this.name = name;
        this.color = color;
        this.price = price;
        this.amount = amount;
    }
public action() {
    }

    public String toString() {
        return "商品：" + name + "\t颜色：" + color + "\t价格：" + price + "\t数量：" + amount;
    }

    public void add() {
        String xString;
        System.out.println("是否要录入商品");
        xString = scanner.next();
        if (xString.equals("是")) {
            System.out.print("商品名称：");
            String name = scanner.next();
            System.out.print("   颜色：");
            String color = scanner.next();
            System.out.print("   价格：");
            String price = scanner.next();
            System.out.print("   数量：");
            String amount = scanner.next();
            action action = new action(name, color, price, amount);
            collection.add(action);
            System.out.println(name + "录入成功！");
        } else {
            System.out.println("返回系统首页！");
        }
    }

    public void show() {
        System.out.println("仓库所有商品信息：");
        for (Object object : collection) {
            System.out.println(object);
        }
    }

    public void delete() {
        Iterator<action> iterator = collection.iterator();
        System.out.println("删除商品的编号为：");
        x = scanner.nextInt();int i = 1;
        while (iterator.hasNext()) {
            if(i==x) {
                iterator.remove();
            }
            Object object= iterator.next();
            System.out.println(object);
            i++;
            
        }
    }
}

public class P146_6杠1库存管理系统 {
    public static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        action action = new action();
        menu();
        while (true) {
            String string;
            System.out.println("输入选择的功能：");string = scanner.next();
            switch (string) {
            case "商品入库功能":
                action.add();
                break;
            case "商品显示功能":
                action.show();
                break;
            case "删除商品功能":
                action.delete();
                break;
            case "退出系统功能":
                System.exit(0);
            default:
                System.out.println("不存在该功能！");
                break;
            }
        }

    }

    public static void menu() {
        System.out.println("库存管理系统：");System.out.println("1.商品入库功能：");
        System.out.println("2.商品显示功能：");
        System.out.println("3.删除商品功能：");
    }
}

对于上面的delete方法中，我是想靠记录循环次数，在指定的循环位置删除对象数据，为啥会报错说我非法，对于迭代器自己的方法它应该是能预支的呀，为啥报错

Answer 1

迭代过程中不可以修改长度