Java：构造函数中的NULL [英] Java: NULL in constructor

问题描述

请问这个问题有点理论化，但我想理解它。

Please I have this question which is a bit theoretical, but I would like to understand it.

为什么我将null参数传递给构造函数？ a NullPointerException ？

Why if I pass a null argument to a constructor do I get a NullPointerException?

这是我的例子

new AttendeeDetail("Gus Goose","1151","15-01-2012",(Integer) null,null) 

这是类：

public class AttendeeDetail {

    private String ticketholder_name;
    private String user_id;
    private String date_of_birth;
    private int tickets_purchased;
    private ArrayList<Ticket> tickets;

    public AttendeeDetail(String ticketholder_name, String user_id, 
        String date_of_birth, int tickets_purchased, ArrayList<Ticket> tickets) 
    {
        this.ticketholder_name=ticketholder_name;
        this.user_id=user_id;
        this.date_of_birth=date_of_birth;
        this.tickets_purchased=tickets_purchased;
        this.tickets=tickets;
    }
}

推荐答案

int 不能 null 。
如果您确实需要传递空值，请使用整数类型

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