object == null或null == object？ [英] object==null or null==object?

问题描述

我从某人那里听说 null == object 优于 object == null check

I heard from somebody that null == object is better than object == null check

例如：

void m1(Object obj ) {
   if(null == obj)  // Is this better than object == null ? Why ?
       return ;
   // Else blah blah
}

有什么理由或这是另一个神话？
感谢您的帮助。

Is there any reasons or this is another myth ? Thanks for help.

推荐答案

这可能是从C学习的习惯，以避免这种错字（单身） = 而不是双 == ）：

This is probably a habit learned from C, to avoid this sort of typo (single = instead of a double ==):

if (object = null) {

== 左侧的常量在Java中并不实用，因为Java要求表达式为 if 求值为 boolean 值，所以除非常量是 boolean ，否则你会得到一个编译错误提出论点。 （如果它是一个布尔值，你不应该使用 == ...）

The convention of putting the constant on the left side of == isn't really useful in Java since Java requires that the expression in an if evaluate to a boolean value, so unless the constant is a boolean, you'd get a compilation error either way you put the arguments. (and if it is a boolean, you shouldn't be using == anyway...)

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