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Consider the Java code: 


Integer i = 3;
foo(i);
System.out.println("i = " + i);

void foo (Integer j) {
  j++;
  System.out.println("j = " + j);
  return; }
Integer is immutable. What is printed?

  • A: Compile error
  • B: Runtime error
  • C: j = 3, i = 3
  • D: j = 4, i = 3
  • E: j = 4, i = 4

    Answer: D

    A pointer to the Integer 3 is passed by value; an Integer 4 (in this case, in the Integer cache) must be found or created for the j++; the original value of i is unchanged.