How to avoid exceptions with Java's equals method

When I somehow investigated how to use equals at work, I found a higher-grade usage, so I will talk about it. I already know this! Please look at it with warm eyes. And please point out any mistakes.

equals method

I think the equals method is often used when comparing strings of the String class. At that time, I used to call it like this.


However, with this call method, if str is null, equals will be called from null, so a *** nullPointerException exception *** will occur.

As a way to avoid this exception, it is ant to check for null with an if statement, but you can avoid the exception by changing the equals method a little.

That's here.


It's easy. It's just the opposite of str and "hoge". This call returns false instead of nullPointerException. Therefore, the *** nullPointerException exception *** will not occur.


This time I introduced the equals method of the String class, but there is also the equals method of the Object class.


This explanation will be on another occasion.


From now on, when using the equals method, I want to call the string first.

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