如何在Java中检查object是否为null？ [英] How to check if object is null in Java?

问题描述

检查职位是否被占用的最佳方法是什么？我不认为我应该使用 this == null ...

What is the best way to check if a position is occupied or not? I don't think I should be using "this==null"...

class Cell {
    int column;
    int row;
    char letter;

    public Cell(int column, int row, char letter) {
        super();
        this.column = column;
        this.row = row;
        this.letter = letter;
    }

    public boolean isEmpty() {
        if (this==null) return true;
        else return false;
    }
}

推荐答案

I我会假设 char 是您的 Cell 的内容，并且您想检查该内容是否 null 。

I'm going to assume that the char is the content of your Cell and you want to check if that content is null.

首先，此永远不能是 null 。 这是当前对象，因此始终存在。

First, this cannot ever be null. this is the current object, and therefore is always exists.

您正在使用 char -因为这是一个原语，也不能为 null 。将其更改为对象包装，并检查 null

You are using a char - as this is a primitive is also cannot be null. Change that to the object wrapper and check that for null

class Cell {

    int column;
    int row;
    Character letter;

    public Cell(int column, int row, Character letter) {
        this.column = column;
        this.row = row;
        this.letter = letter;
    }

    public boolean isEmpty() {
        return letter == null;
    }
}

另一个要注意的是，超类构造函数总是由默认情况下，没有理由调用 super（）。

Another note is that the superclass constructor is always called by default, there is no reason to call super().

这篇关于如何在Java中检查object是否为null？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！