Varargs Null Checking
May 8th, 2009
VarArgs Null checking? This should be easy, right? All we need to do is put a “VarArgs”.length == 0 check before the important method’s body and we are set (See Checker class), correct?
class Checker {
public void check(Arg... args){
if(args.length == 0) return;
final List<Arg> someArgs = Arrays.asList(args);
for(Arg each: someArgs){
System.out.println("checked:" + each.toString());
}
}
}
class Arg{
private final String name;
Arg(String name){this.name = name;}
@Override public String toString(){return name;}
}
The above check should work nicely under the following circumstances
new Checker().check(new Arg("one"), new Arg("two"));
new Checker()
Unfortunately, it won’t work under the following one, which will actually throw the exception that you were trying to avoid: NullPointerException.
new Checker().check(null, null); // Ooh! a NullPointerException....
how to fix this? Easy…
class Checker {
public void check(Arg... args){
if(args.length == 0 || Arrays.asList(args).contains(null)) return;
final List<Arg> someArgs = Arrays.asList(args);
for(Arg each: someArgs){
System.out.println(each.toString());
}
}
}
This should definitely work nicely. This is all for today. Until next time.
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