Oracle Certified Associate Java Se 8 Programmer · Free Practice Question Hard
Question 5
What will be the result of compiling and executing the following program?
public class Main {
public static void main(String[] args) {
process(1);
}
private static void process(Object obj) {
System.out.println("Object version");
}
private static void process(Number obj) {
System.out.println("Number version");
}
private static void process(Double obj) {
System.out.println("Double version");
}
}
-
A
Double version
-
B
Compilation error
-
C
Number version
-
D
Object version
Reveal correct answer
Correct answer: C
Explanation
There are 3 overloaded methods process. Note all the numeric wrapper classes (Byte, Short, Integer, Long, Float, and Double) extend from Number, and Number extends from Object. The compiler either does implicit casting or Wrapping but not both. 1 is an int literal; the Java compiler can't implicitly cast it to double and then box it to Double, rather it boxes it to Integer and since Number is the immediate superclass of Integer, so the Number version refers to the Integer object. "Number version" is printed on the console.
Discussion
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