When I try to concatenate a String that is actually null with a valid string (eg "a"), I get the value nulla . See the example below:
String a = "a";
String b = null;
System.out.println(b + a);
I wanted the output to be just "a". Is there any way to do this without checking whether String is null ?
You should not try to concatenate a null with a text. I even think java should either prohibit concatenation in this case, or adopt an empty string when it encounters a null (each has pros and cons). As it is not so, the solution is this:
System.out.println((b == null ? "" : b) + a);
See working on ideone .
Obviously you can create a utility method to do this generically and use it whenever you need it.
If it is guaranteed that a has a value and only b can be null, you can follow what was answered by Bigown.
If you are not sure and / or need to test a larger number of strings, it may be more interesting to use Optional to check if an object is null. And if this is, return some pre-defined value that will not disturb the concatenation (an empty string maybe ?!):
public static String get(String string){
return Optional.ofNullable(string).orElse("");
}
Using:
String a = "a", b = null, c = "c";
get(a) + get(b); // "a"
get(a) + get(b) + get(c); // "ac"
get(b); // ""
I believe that instead of setting a String variable to "null" you should set it to "". For example:
public static void main(String[] args) {
String a = "a";
String b = "";
System.out.println(a+b);
}
So it already returns the correct one;