I'm new in java programming. Now I have a problem when I have String variable equals to null. When I check condition on that String it error :
Exception in thread "main" java.lang.NullPointerException.
This is my code :
public class Test {
static String a=null;
public static void main(String[] args) {
if(a.equals(null)){
System.out.println("Null");
}
}
}
Instead of a.equals(null) you should be doing a == null.
if(a == null) {
System.out.println("Null");
}
Alternatively, you can use the StringUtils to check if String is null or empty by doing:
if(StringUtils.isEmpty(a)) {
System.out.println("Null");
}
a itself is null, it will be null.equals() and it does not hold good. You can't invoke a method on a null object.
null reference. There's no such thing as a null object. It's worth keeping the distinction between variables, references and objects very clear.If there is a potential for both references to be null, you can use
Objects.equals(a, b)
Check with == or != like:
if(a!=null){
System.out.println("is not Null");
}
if statement doesn't have to be a Boolean type, but it makes no sense in Java for situations like this.
If you want to check for null
if(a == null){
System.out.println("I am null");
}
If you want to check for empty or blank String
if(a != null && a.length() == 0){
System.out.println("I am an empty String");
}
