Given: public class Person { private String name; public Person(String name) { this.name = name; } public String toString() { return name; } } and public class Tester { public static void…

Question

Options

• AJoeMarry
• BJoeNull
• CNullNull
• DNullMary

• A
  3% (1)
• B
  17% (5)
• C
  7% (2)
• D
  72% (21)

Explanation

Option D is correct because Java is pass-by-value: when p is passed to checkPerson, the method receives a copy of the reference, so reassigning the parameter inside the method never changes what p points to back in main. After the first call (p = null), checkPerson creates "Joe" internally and the return value is ignored - p in main remains null. After p = new Person("Mary"), the second call sets the local copy to null, but again the return value is ignored, so p in main still points to "Mary" when println runs - producing the output Mary.

Why the distractors fail:

• A (JoeMarry) assumes the first checkPerson call changed main's p to Joe - it didn't.
• B (JoeNull) assumes both calls mutated main's p - neither did.
• C (NullNull) correctly identifies the first state but wrongly assumes the second call sets main's p to null.

Memory tip: Think of a reference variable as a house address on a sticky note. Passing it to a method gives the method its own sticky note with the same address - the method can scribble on its note all it wants, but your original note doesn't change.

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