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SCJP Mock exam for Generics

By Nikos

If you are busy, just go through questions 1-40.

questions topic
1-24 assignment and hierarchy
25-40 add and get elements from a generic collection
41-50 overloading and overriding
51-60 various details
61-72 declaration of generic classes
  1. Will this code compile successfully? (1 correct answer) 
    List<Number> list1 = null;
List<Integer> list2 = null;
list1 = list2;
    1. Yes.
    2. No.

  2. Will this code compile successfully? (1 correct answer) 
    List<Number> list1 = null;
List<Integer> list2 = null;
list2 = list1;
    1. Yes.
    2. No.

  3. Will this code compile successfully? (1 correct answer) 
    List<? extends Number> list1 = null;
List<Integer> list2 = null;
list1 = list2;
    1. Yes.
    2. No.

  4. Will this code compile successfully? (1 correct answer) 
    List<? extends Number> list1 = null;
List<Integer> list2 = null;
list2 = list1;
    1. Yes.
    2. No.

  5. Will this code compile successfully? (1 correct answer) 
    List<Number> list1 = null;
List<? super Integer> list2 = null;
list1 = list2;
    1. Yes.
    2. No.

  6. Will this code compile successfully? (1 correct answer) 
    List<Number> list1 = null;
List<? super Integer> list2 = null;
list2 = list1;
    1. Yes.
    2. No.

  7. Will this code compile successfully? (1 correct answer) 
    SortedSet<? super Number> set1 = null;
SortedSet<Integer> set2 = null;
set1 = set2;
    1. Yes.
    2. No.

  8. Will this code compile successfully? (1 correct answer) 
    SortedSet<? super Number> set1 = null;
SortedSet<Integer> set2 = null;
set2 = set1;
    1. Yes.
    2. No.

  9. Will this code compile successfully? (1 correct answer) 
    SortedSet<Number> set1 = null;
SortedSet<? extends Integer> set2 = null;
set1 = set2;
    1. Yes.
    2. No.

  10. Will this code compile successfully? (1 correct answer) 
    SortedSet<Number> set1 = null;
SortedSet<? extends Integer> set2 = null;
set2 = set1;
    1. Yes.
    2. No.

  11. Will this code compile successfully? (1 correct answer) 
    Queue<? extends Number> q1 = null;
Queue<? super Integer> q2 = null;
q1 = q2;
    1. Yes.
    2. No.

  12. Will this code compile successfully? (1 correct answer) 
    Queue<? extends Number> q1 = null;
Queue<? super Integer> q2 = null;
q2 = q1;
    1. Yes.
    2. No.

  13. Will this code compile successfully? (1 correct answer) 
    Queue<? super Number> q1 = null;
Queue<? extends Integer> q2 = null;
q1 = q2;
    1. Yes.
    2. No.

  14. Will this code compile successfully? (1 correct answer) 
    Queue<? super Number> q1 = null;
Queue<? extends Integer> q2 = null;
q2 = q1;
    1. Yes.
    2. No.

  15. Will this code compile successfully? (1 correct answer) 
    Queue<?> q1 = null;
Queue<Integer> q2 = null;
q1 = q2;
    1. Yes.
    2. No.

  16. Will this code compile successfully? (1 correct answer) 
    LinkedList<?> list1 = null;
LinkedList<Integer> list2 = null;
list2 = list1;
    1. Yes.
    2. No.

  17. Will this code compile successfully? (1 correct answer) 
    LinkedList<?> list1 = null;
LinkedList<? extends Integer> list2 = null;
list1 = list2;
    1. Yes.
    2. No.

  18. Will this code compile successfully? (1 correct answer) 
    LinkedList<?> list1 = null;
LinkedList<? extends Integer> list2 = null;
list2 = list1;
    1. Yes.
    2. No.

  19. Will this code compile successfully? (1 correct answer) 
    LinkedList<?> list1 = null;
LinkedList<? super Integer> list2 = null;
list1 = list2;
    1. Yes.
    2. No.

  20. Will this code compile successfully? (1 correct answer) 
    LinkedList<?> list1 = null;
LinkedList<? super Integer> list2 = null;
list2 = list1;
    1. Yes.
    2. No.

  21. Will this code compile successfully? (1 correct answer) 
    PriorityQueue queue1 = null;
PriorityQueue<Integer> queue2 = null;
queue1 = queue2;
    1. Yes, without warnings.
    2. Yes, with a warning.
    3. No.

  22. Will this code compile successfully? (1 correct answer) 
    PriorityQueue queue1 = null;
PriorityQueue<Integer> queue2 = null;
queue2 = queue1;
    1. Yes, without warnings.
    2. Yes, with a warning.
    3. No.

  23. Will this code compile successfully? (1 correct answer) 
    PriorityQueue<?> queue1 = null;
PriorityQueue queue2 = null;
queue1 = queue2;
    1. Yes, without warnings.
    2. Yes, with a warning.
    3. No.

  24. Will this code compile successfully? (1 correct answer) 
    PriorityQueue<?> queue1 = null;
PriorityQueue queue2 = null;
queue1 = queue2;
    1. Yes, without warnings.
    2. Yes, with a warning.
    3. No.

  25. Will this code compile successfully? (1 correct answer) 
    Set<Integer> set = new TreeSet<Integer>();
set.add(10);
    1. Yes.
    2. No.

  26. Will this code compile successfully? (1 correct answer) 
    Set<Integer> set = new TreeSet<Integer>();
set.add((int)1.0f);
    1. Yes.
    2. No.

  27. Will this code compile successfully? (1 correct answer) 
    Set<Integer> set = new TreeSet<Integer>();
set.add(10L);
    1. Yes.
    2. No.

  28. Will this code compile successfully? (1 correct answer) 
    Set<Integer> set = new TreeSet<Integer>();
int number = (short)10;
set.add(number);
    1. Yes.
    2. No.

  29. Will this code compile successfully? (1 correct answer) 
    Set<Number> set = new TreeSet<Integer>();
set.add(10L);
    1. Yes.
    2. No.

  30. Will this code compile successfully? (1 correct answer) 
    NavigableSet<?> set = new TreeSet<Object>();
set.add(new Object());
    1. Yes.
    2. No.

  31. Will this code compile successfully? (1 correct answer) 
    NavigableSet<? super Object> set = new TreeSet<Object>();
set.add(new Object());
    1. Yes.
    2. No.

  32. Will this code compile successfully? (1 correct answer) 
    NavigableSet<? extends Object> set = new TreeSet<Object>();
set.add(new Object());
    1. Yes.
    2. No.

  33. Will this code compile successfully? (1 correct answer) 
    NavigableSet<? extends String> set = new TreeSet<String>();
set.add("string");
    1. Yes.
    2. No.

  34. Will this code compile successfully? (1 correct answer) 
    NavigableSet<? super String> set = new TreeSet<String>();
set.add("string");
    1. Yes.
    2. No.

  35. Will this code compile successfully? (1 correct answer) 
    NavigableSet<? super String> set = new TreeSet<String>();
set.add(new Object());
    1. Yes.
    2. No.

  36. Will this code compile successfully? (1 correct answer) 
    List<? extends Integer> list = new ArrayList<Integer>();
for (Integer element : list) {
	System.out.println(element);
}
    1. Yes.
    2. No.

  37. Will this code compile successfully? (1 correct answer) 
    List<? extends Integer> list = new ArrayList<Integer>();
Integer first = list.get(0);
    1. Yes.
    2. No.

  38. Will this code compile successfully? (1 correct answer) 
    List<? super Integer> list = new ArrayList<Integer>();
for (Integer element : list) {
	System.out.println(element);
}
    1. Yes.
    2. No.

  39. Will this code compile successfully? (1 correct answer) 
    List<? super Integer> list = new ArrayList<Integer>();
Integer first = list.get(0);
    1. Yes.
    2. No.

  40. Will this code compile successfully? (1 correct answer) 
    List<? super Integer> list = new ArrayList<Integer>();
Object first = list.get(0);
    1. Yes.
    2. No.

  41. Will this code compile successfully? (1 correct answer) 
    import java.util.*;

class Test {
    void say(Set<Double> set) {
    }
    void say(SortedSet<Double> set) {
    }
}
    1. Yes.
    2. No.

  42. Will this code compile successfully? (1 correct answer) 
    import java.util.*;

class Test {
    void say(Set<Double> set) {
    }
    void say(Set<Boolean> set) {
    }
}
    1. Yes.
    2. No.

  43. Will this code compile successfully? (1 correct answer) 
    import java.util.*;

class Test {
    void say(Set<Double> set) {
    }
    void say(Set<Double>... set) {
    }
}
    1. Yes.
    2. No.

  44. Consider these classes. 
    import java.util.*;

class Parent {
	void say(List<String> list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List list) {
		System.out.println("child");
	}
}

    What happens when this code is compiled and executed? (1 correct answer)

    public static void main(String[] java) {
	Child c = new Child();
	c.say(new LinkedList<String>());
}
    1. It prints “child”.
    2. It prints “parent”.
    3. Compilation fails.

  45. Consider these classes. 
    import java.util.*;

class Parent {
	void say(List<String> list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List list) {
		System.out.println("child");
	}
}

    What happens when this code is compiled and executed? (1 correct answer)

    public static void main(String[] java) {
	Child c = new Child();
	c.say(new LinkedList<List<Boolean>>());
}
    1. It prints “child”.
    2. It prints “parent”.
    3. Compilation fails.

  46. Consider these classes. 
    import java.util.*;

class Parent {
	void say(List<String> list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List list) {
		System.out.println("child");
	}
}

    What happens when this code is compiled and executed? (1 correct answer)

    public static void main(String[] java) {
	Parent c = new Child();
	c.say(new LinkedList<String>());
}
    1. It prints “child”.
    2. It prints “parent”.
    3. Compilation fails.

  47. Consider these classes. 
    import java.util.*;

class Parent {
	void say(List<String> list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List list) {
		System.out.println("child");
	}
}

    What happens when this code is compiled and executed? (1 correct answer)

    public static void main(String[] java) {
	Parent c = new Child();
	c.say(new LinkedList<Long>());
}
    1. It prints “child”.
    2. It prints “parent”.
    3. Compilation fails.

  48. Will this code compile successfully? (1 correct answer) 
    import java.util.*;

class Parent {
	void say(List<String> list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List<Integer> list) {
		System.out.println("child");
	}
}
    1. Yes.
    2. No.

  49. Will this code compile successfully? (1 correct answer) 
    import java.util.*;

class Parent {
	void say(List<? extends Number> list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List<Integer> list) {
		System.out.println("child");
	}
}
    1. Yes.
    2. No.

  50. Will this code compile successfully? (1 correct answer) 
    import java.util.*;

class Parent {
	void say(List list) {
		System.out.println("parent");
	}
}
class Child extends Parent {
	void say(List<Integer> list) {
		System.out.println("child");
	}
}
    1. Yes.
    2. No.

  51. Will this code compile successfully? (1 correct answer) 
    Object set = new TreeSet<Integer>();
boolean flag = set instanceof NavigableSet<Integer>;
    1. Yes.
    2. No.

  52. What is the output of the following code? (1 correct answer) 
    List<? extends String> list1 = new ArrayList<String>();
List<? super String> list2 = new ArrayList<String>();
List<Integer> list3 = new ArrayList<Integer>();
List list4 = new ArrayList();

if (list1 instanceof List &&
    list2 instanceof List &&
    list3 instanceof List &&
    list4 instanceof List) {
    System.out.println("yes");
}
    1. It prints “yes”.
    2. It prints nothing.

  53. Will this code compile successfully? (1 correct answer) 
    Class c = ArrayList<Integer>.class;
    1. Yes.
    2. No.

  54. Will this code compile successfully? (1 correct answer) 
    Class c = new ArrayList<Integer>().getClass();
    1. Yes.
    2. No.

  55. Will this code compile successfully? (1 correct answer) 
    new ArrayList<?>();
    1. Yes.
    2. No.

  56. Will this code compile successfully? (1 correct answer) 
    new TreeMap<String, ? super Integer>();
    1. Yes.
    2. No.

  57. Will this code compile successfully? (1 correct answer) 
    new ArrayList<Set<?>>();
    1. Yes.
    2. No.

  58. Will this code compile successfully? (1 correct answer) 
    class Test extends ArrayList<? extends Number> {
}
    1. Yes.
    2. No.

  59. Will this code compile successfully? (1 correct answer) 
    class Test implements Comparable<?> {
    public int compareTo(Comparable<?> object) {
        return 0;
    }
}
    1. Yes.
    2. No.

  60. Will this code compile successfully? (1 correct answer) 
    class Test implements Comparable<Comparable<?>> {
    public int compareTo(Comparable<?> object) {
        return 0;
    }
}
    1. Yes.
    2. No.

  61. Will this code compile successfully? (1 correct answer) 
    class Test {
<T> T getFirst(List<T> list) {
    return list.get(0);
}
}
    1. Yes.
    2. No.

  62. Will this code compile successfully? (1 correct answer) 
    class Test {
static <T> T getFirst(List<T> list) {
    return list.get(0);
}
}
    1. Yes.
    2. No.

  63. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
T getFirst(List<T> list) {
    return list.get(0);
}
}
    1. Yes.
    2. No.

  64. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
static T getFirst(List<T> list) {
    return list.get(0);
}
}
    1. Yes.
    2. No.

  65. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
T instance;
Test(T instance) {
    this.instance = instance;
}
}
    1. Yes.
    2. No.

  66. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
Test(T my) {
    boolean b = (my instanceof T);
}
}
    1. Yes.
    2. No.

  67. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
void test(T method) {
    Object my = (T)method;
}
}
    1. Yes.
    2. No.

  68. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
void test() {
    NavigableMap map = new TreeMap<String, T>();
}
}
    1. Yes.
    2. No.

  69. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
private T[] array = null;
}
    1. Yes.
    2. No.

  70. Will this code compile successfully? (1 correct answer) 
    class Test <T> {
private T[] array = new T[7];
}
    1. Yes.
    2. No.

  71. Will this code compile successfully? (1 correct answer) 
    class Test<String> {
    String my = "Hello!";
}
    1. Yes.
    2. No.

  72. Will this code compile successfully? (1 correct answer) 
    class Test<String> {
    String my;
    public Test(String my) {
        this.my = my;
    }
    public String get() {
        return my;
    }
}

public class RunTest {
    public static void main(String[] args) {
        Integer i = new Test<Integer>(1).get();
        System.out.println(i.getClass());
    }
}
    1. Yes.
    2. No.

© 2008 Nikos Pougounias. This is a free contribution to the Java community. Please distribute it for free. http://nikojava.wordpress.com

Answers

  1. b
  2. b
  3. a
  4. b
  5. b
  6. a
  7. b
  8. b
  9. b
  10. b
  11. b
  12. b
  13. b
  14. b
  15. a
  16. b
  17. a
  18. b
  19. a
  20. b
  21. a
  22. b
  23. a
  24. a
  25. a
  26. a
  27. b
  28. a
  29. b
  30. b
  31. a
  32. b
  33. b
  34. a
  35. b
  36. a
  37. a
  38. b
  39. b
  40. a
  41. a
  42. b
  43. a
  44. a
  45. a
  46. a
  47. c
  48. b
  49. b
  50. b
  51. b
  52. a
  53. b
  54. a
  55. b
  56. b
  57. a
  58. b
  59. b
  60. a
  61. a
  62. a
  63. a
  64. b
  65. a
  66. b
  67. a
  68. a
  69. a
  70. b
  71. b
  72. a

Tags:

This entry was posted on 9 October 2008 at 8:32 pm and is filed under SCJP 6, Training. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

9 Responses to “SCJP Mock exam for Generics”

  1. Free SCJP Mock exams « Niko’s java blog Says:
    30 December 2008 at 7:47 pm

    [...] java blog quick & easy Java tutorials « SCJP Mock exam for Generics JBoss integration with JDeveloper 11g [...]

  2. Aruna Says:
    2 February 2009 at 11:39 am

    Hii Niko This an Excellent Practice Stuff.it’s helped me a lot in grasping the Concepts of Generics fully.
    Thnaks A Lot.

  3. JacQ Says:
    9 March 2009 at 4:02 pm

    Thx ! :) nice one

  4. himalay Says:
    11 March 2009 at 3:50 pm

    kudos to you

  5. Ahsan Jamshaid Says:
    23 March 2009 at 1:24 pm

    Hi Niko,
    this is really excellent stuff. i liked it and i really appreciate your effort.

    Thanks Buddy!..

  6. Paolo Says:
    10 April 2009 at 11:06 am

    Hi, thanks for this!

    Questions 23 and 24 and respective answers are identical. Is it intended?

  7. ajith Says:
    12 April 2009 at 8:27 am

    hi Niko,,,
    thanks a lot …. i really enjoyed with these questions …
    well done

  8. unexpected compilation error with Generics : java cms Says:
    15 April 2009 at 6:11 am

    [...] This is from the practice exam for Generics on > NikoJava [...]

  9. The true about the question 72?? Says:
    24 October 2009 at 1:55 am

    Hi everyone

    In question 72 the correct answer is b), i don’t know the exact reason; I supposed is a name colide because i tried to compile and the result is:

    non-static class String cannot be referenced from a static context

    Thanks for your time

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