Java common mistake for beginners

Hi, Java beginner! Welcome to the world of programming, where endless possibilities await you. However, as a newbie, you may come across some common mistakes. Don’t worry! In this article, I will share with you some easy mistakes and give the right cases. Let’s get started!

Null pointer exception of reference type

A null pointer exception is one of the most common exceptions in Java programming. It is usually caused by an attempt to call a method or access a field on a null reference variable. Here is an example of an error that produces a null pointer exception:

String name = null;
System.out.println(name.length());

In the above example, we try to get the length of a null reference variable name , which results in a null pointer exception. To avoid this error, we should do a null reference check before using the reference type, for example:

String name = null;
if (name != null) {
    System.out.println(name.length());
} else {
    System.out.println("name is null");
}

In this way, we check whether the length property of name is null before accessing it. If it is null, we can take appropriate measures to avoid null pointer exceptions.

Confusing equal sign and assignment sign