Quiz 3

1. Which statements are true? Select the two correct answers.

(A) In Java, the extends clause is used to specify the inheritance relationship.

(B) The subclass of a non-abstract class can be declared abstract.

(C) All members of the superclass are inherited by the subclass.

(D) A final class can be abstract.

(E) A class in which all the members are declared private, cannot be declared public.

• (A) and (B)

• (B) and (C)

• (A) and (E)

• (C) and (D)

• (D) and (E)

2. Which statements are true? Select the two correct answers.

(A) A class can only be extended by one class.

(B) Every Java object has a public method named equals.

(C) Every Java object has a public method named length.

(D) A class can extend any number of classes.

(E) A non-final class can be extended by any number of classes.

• (B) and (C)

• (A) and (B)

• (B) and (E)

• (C) and (D)

• (D) and (E)

Given the following classes and declarations, which statements are true?  Select the three correct answers.

(A) The Bar class is a subclass of Foo.

(B) The statement b.f(); is legal.

(C) The statement a.j = 5; is legal.

(D) The statement a.g(); is legal.

(E) The statement b.i = 3; is legal.

• (A), (B) and (D)

• (A), (C) and (E)

• (C), (D) and (E)

• (B), (C) and (D)

• (A), (D) and (E)

Given classes A, B, and C, where B extends A, and C extends B, and where all classes implement the instance method void doIt(). How can the doIt() method in A be called from an instance method in C? Select the one correct answer.

• super.doIt();

• super.super.doIt();

• this.super.doIt();

• A.this.doIt();

• ((A) this).doIt();

Which method declarations, when inserted at (7), will not result in a compile-time error?  Select the two correct answers.

(A) public int step1(int i) { return 1; }

(B) public String step2(String str2, String str1) { return str1; }

(C) private void step2() { } (D) private static void step2() { }

(E) private static String step2(String str) { return str; }

(F) public MySuperclass makeIt() { return new MySuperclass(); }

(G) public MyClass makeIt2() { return new MyClass(); }

• (B) and (G)

• (A) and (E)

• (C) and (D)

• (F) and (G)

• (C) and (F)

What would be the result of compiling and running the following program? Select the one correct answer.

• The code will compile and print |Toyota|Volvo|12345|54321|, when run.

• The code will compile and print |Volvo|Toyota|12345|54321|, when run.

• The code will compile and print |Toyota|Toyota|12345|12345|, when run.

• The code will compile and print |Toyota|Toyota|12345|12345|, when run.

• The code will compile and print |Volvo|Toyota|54321|54321|, when run.

Which of these field declarations are legal within the body of an interface? Select the two correct answers.

(A) public static int answer = 42;

(B) int answer;

(C) final static int answer = 42;

(D) public int answer = 42;

(E) private final static int answer = 42;

• (A) and (B)

• (A) and (C)

• (C) and (E)

• (D) and (E)

• (B) and (D)

Which statement is true about the following code? Select the one correct answer.

• MyClass only implements Interface1. Implementation for void h() from Interface2 is missing.

• The declarations of void g() in the two interfaces conflict, therefore, the code will not compile.

• The declarations of int VAL_B in the two interfaces conflict, therefore, the code will not compile.

• Nothing is wrong with the code, it will compile without errors.

Which declaration can be inserted at (1) without causing a compilation error? Select the two correct answers.

(A) final double circumference = 2 Math.PI * r;

(B) int total = total + r + s;

(C) int AREA = r * s;

(D) public static MAIN = 15;

(E) protected int CODE = 31337;

• (E) and (B)

• (D) and (A)

• (B) and (D)

• (A) and (C)

• (C) and (D)

Given the following type and reference declarations, which assignment is legal? Select the one correct answer.

• obj2 = obj1;

• obj3 = obj1;

• obj3 = obj2;

• I1 a = obj2;

• I1 b = obj3;