### Question:
IntList { public static IntList dcatenate(IntList A, IntList B) { if (A == null) { return B; } IntList p = A; while (p.rest != null) { p = p.rest; } p.rest = B; return A; } IntList(int first0, IntList rest0);  IntList(); static void dSquareList(IntList L); static IntList squareListIterative(IntList L); static IntList squareListRecursive(IntList L); static IntList dcatenate(IntList A, IntList B); static IntList catenate(IntList A, IntList B); @Override int hashCode(); static IntList of(Integer... args); boolean equals(Object x); @Override /** Outputs the IntList as a String. You are not expected to read * or understand this method. */ String toString(); public int first; public IntList rest; }### Answer:
@Test public void testDcatenate() { IntList A = IntList.of(1, 2, 3); IntList B = IntList.of(4, 5, 6); IntList exp = IntList.of(1, 2, 3, 4, 5, 6); assertEquals(exp, IntList.dcatenate(A, B)); assertEquals(IntList.of(1, 2, 3, 4, 5, 6), A); }