java - 链表仅适用于第一个链表

Question

所以我试图用java查看Linkedlist中的所有数据。 它们看起来像这样:

private List <Customer> customers;
public databse(){
customers.add(new Customer(101, "Allen", 10))
customers.add (new Customer(102, "John", 15))
customers.add (new Customer(103, "Lucy", 23))
}

然后我尝试使用此根据 id 查看客户

   private void customer(){
   System.out.println(" ");
   System.out.print("Enter a customer ID: ");
   int id = In.nextInt();
   for(Customer customer:customers )
   {
        if(customer.getID() == id){
            System.out.println(customer.toString());
            System.out.println(" ");
           // break;
          }
          else 
        {System.out.println("That customer does not exist.");
        System.out.println(" ");

        }
        System.out.println(" ");
     break;           
   }

然后我得到这个作为输出:

Enter a customer ID: 101
101 Allen   10

但是，如果我尝试查看 102 或 103，则不起作用

Enter a customer ID: 102 
That customer does not exist.

可能是什么问题？ Allen 和 Customer 类已被调用。

Answer 1

问题出在你的循环中，你检查第一个元素，然后打印它或“循环突破”。您的其余项目永远不会被检查。

相反，您应该跟踪是否找到了对象。

private void customer(){
    System.out.println(" ");
    System.out.print("Enter a customer ID: ");
    int id = In.nextInt();
    boolean found = false;
    for(Customer customer:customers ) {
        if(customer.getID() == id){
            System.out.println(customer.toString());
            System.out.println(" ");
            found = true;
            break;
        }
    }
    if (!found) {
        System.out.println("That customer does not exist.");
        System.out.println(" ");
    }
}