var a: String? = "abc" // can be set null a = null // value set to null val l = if (a != null) a. To avoid this error we have to check if b is null and handle two cases in a respective manner. What initially sounds like cumbersome extra work. To allow nulls, we have to declare a variable as a nullable string, which can be done by adding a “?” to the data type i.e, “String? ”.The nullable counterpart of some type A is denoted as A? var a: String? = "abc" // this is a nullable string b = null // value is set to null print(a) // null printedīut in this case, there are chances of NPE error when a method or property is accessed. In fact, in Kotlin, for each declaration of a variable, one has to indicate whether it can ever become null. In Kotlin a normal data type like string cannot store a null value and trying to do so will cause an error.
This is done to eliminate the NullPointerException error in the code which is common in other programming languages like Java.
If we create a standard variable in Kotlin, we can't assign the null value to it: // This code won't work var number 15 number null // This line will cause an error That's because someone may not be expecting null there. In Kotlin by default, the data types are of non-nullable types i.e trying to assign a value as null would cause an error. For this purpose, a special null value was introduced, which safely indicates that a variable is empty.
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