If doSomething
is overloaded, you need to cast the null explicitly to MyClass
so the right overload is chosen:
public void doSomething(MyClass c) {
// ...
}
public void doSomething(MyOtherClass c) {
// ...
}
A non-contrived situation where you need to cast is when you call a varargs function:
class Example {
static void test(String code, String... s) {
System.out.println("code: " + code);
if(s == null) {
System.out.println("array is null");
return;
}
for(String str: s) {
if(str != null) {
System.out.println(str);
} else {
System.out.println("element is null");
}
}
System.out.println("---");
}
public static void main(String... args) {
/* the array will contain two elements */
test("numbers", "one", "two");
/* the array will contain zero elements */
test("nothing");
/* the array will be null in test */
test("null-array", (String[])null);
/* first argument of the array is null */
test("one-null-element", (String)null);
/* will produce a warning. passes a null array */
test("warning", null);
}
}
The last line will produce the following warning:
Example.java:26: warning: non-varargs
call of varargs method with inexact
argument type for last parameter;
cast tojava.lang.String
for a varargs
call
cast tojava.lang.String[]
for a
non-varargs call and to suppress this
warning