Certified Java Programmer Mock Exam

Question 1

class A {
  public static void main(String[] args) {
    char a = 'a'; // 'a' = 97
    char b = 'b'; // 'b' = 98
    System.out.print(a + b + "" + a + b);
}}

What is the result of attempting to compile and run the program?

Question 2

interface I1 {}
interface I2 {}
class Base implements I1 {}
class Sub extends Base implements I2 {}
class Red {
  public static void main(String args[]) {
    Sub s1 = new Sub();
    I2 i2 = s1;          // 1
    I1 i1 = s1;          // 2
    Base base = s1;      // 3
    Sub s2 = (Sub)base;  // 4
}}

A compile-time error is generated at which line?

Question 3

interface I1 {}
interface I2 {}
class Base implements I1 {}
class Sub extends Base implements I2 {}
class Orange {
  public static void main(String args[]) {
    Base base = new Base();
    I1 i1 = base;           // 1
    Sub sub = (Sub)base;    // 2
}}

What is the result of attempting to compile and run the program?

Question 4

interface I1 {}
interface I2 {}
class Base implements I1 {}
class Sub extends Base implements I2 {}
class Yellow {
  public static void main(String args[]) {
    Base base = new Sub();  // 1
    I1 i1 = base;           // 2
    Sub sub = (Sub)base;    // 3
    I2 i2 = (Sub)base;      // 4
}}

A compile-time error is generated at which line?

Question 5

interface I1 {}
interface I2 {}
class Base implements I1 {}
class Sub extends Base implements I2 {}
class Gray {
  public static void main(String []args) {
  Base[] base = {new Base()};  // 1
  Sub sub[] = {new Sub()};     // 2
  Object obj = sub;            // 3
  base = obj;                  // 4
}}

A compile-time error is generated at which line?

Question 6

interface I1 {}
interface I2 {}
class Base implements I1 {}
class Sub extends Base implements I2 {}
class Silver {
  public static void main(String []args) {
    Base[] base = {new Base()};
    Sub sub[] = new Sub[1];    // 1
    Object obj = base;         // 2
    sub = (Sub[])obj;          // 3
    I1 []i1 = (I1[])obj;       // 4
}}

What is the result of attempting to compile and run the program?