Java Programmer Certification Mock Exam

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Question 1

 •Elements are not key/value pairs.
 •Contains no duplicate elements.
 •The entries can be sorted using the Comparable interface.

Which of these classes provides the specified features?

a. LinkedList
b. TreeMap
c. TreeSet
d. HashMap
e. HashSet
f. Hashtable
g. None of the above

Question 2

import java.util.*;
class GFC106 {
  public static void main (String args[]) {
    Object a = new HashSet(), b = new HashMap();
    Object c = new Hashtable();
    System.out.print((a instanceof Map)+",");
    System.out.print((b instanceof Map)+",");
    System.out.print(c instanceof Map);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 3

class A {
  int i1, i2;
  public void setI1(int i) {i1 = i;}
  public int getI1() {return i1;}
  public void setI2(int i) {i2 = i;}
  public int getI2() {return i2;}
  public A(int ii1, int ii2) {i1 = ii1; i2 = ii2;}
  public boolean equals(Object obj) {
    if (obj instanceof A) {
      return (i1 == ((A)obj).getI1());
    }
    return false;
  }
  public int hashCode() {
    // Insert statement here.
}}

Which of the following statements could be inserted at the specified location without violating the hash code contract?

a. return 31;
b. return getI1();
c. return getI2();
d. return 31 * getI1() + getI2();

Question 4

 •Stores key/value pairs.
 •Allows null elements, keys, and values.
 •Duplicate entries replace old entries.
 •Entries are not sorted.

Which of these classes provides the specified features?

a. LinkedList
b. TreeMap
c. TreeSet
d. HashMap
e. HashSet
f. Hashtable
g. None of the above

Question 5

import java.util.*;
class GFC107 {
  public static void main (String args[]) {
    Object a = new HashSet(), b = new HashMap();
    Object c = new Hashtable();
    System.out.print((a instanceof Cloneable)+",");
    System.out.print((b instanceof Cloneable)+",");
    System.out.print(c instanceof Cloneable);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 6

class A {
  int i1, i2;
  public void setI1(int i) {i1 = i;}
  public int getI1() {return i1;}
  public void setI2(int i) {i2 = i;}
  public int getI2() {return i2;}
  public A(int ii1, int ii2) {i1 = ii1; i2 = ii2;}
  public boolean equals(Object obj) {
    if (obj instanceof A) {
      return (i1 == ((A)obj).getI1()) & (i2 == ((A)obj).getI2());
    }
    return false;
  }
  public int hashCode() {
    // Insert statement here.
}}

If inserted at the specified location, which of the following statements would produce the most efficient hashCode method?

a. return 31;
b. return getI1();
c. return getI2();
d. return getI1() + getI2();
e. return 31 * getI1() + getI2();
f. None of the above

Question 7

 •Entries are not organized as key/value pairs.
 •Generally accepts duplicate elements.
 •Entries may be accessed by means of an index.

Which interface of the java.util package offers the specified behavior?

a. List
b. Map
c. Set
d. None of the above

Question 8

import java.util.*;
import java.io.Serializable;
class GFC108 {
  public static void main (String args[]) {
    HashMap a = new HashMap();
    boolean b1, b2, b3;
    b1 = (a instanceof Cloneable) & (a instanceof Serializable);
    b2 = a instanceof Map;
    b3 = a instanceof Collection;
    System.out.print(b1 + "," + b2 + "," + b3);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 9

Which of the following classes allow unsynchronized read operations by multiple threads?

a. Vector
b. Hashtable
c. TreeMap
d. TreeSet
e. HashMap
f. HashSet

Question 10

 •Entries are organized as key/value pairs.
 •Duplicate entries replace old entries.
 •Entries are sorted using a Comparator or the Comparable interface.

Which interface of the java.util package offers the specified behavior?

a. List
b. Map
c. Set
d. SortedSet
e. SortedMap
f. None of the above

Question 11

import java.util.*;
class GFC110 {
  public static void main (String[] args) {
    Object m = new LinkedHashMap();
    System.out.print((m instanceof Collection)+",");
    System.out.print((m instanceof Map)+",");
    System.out.print(m instanceof List);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 12

 •Entries are not organized as key/value pairs.
 •Duplicate entries are rejected.
 •Entries are sorted using a Comparator or the Comparable interface.

Which interface of the java.util package offers the specified behavior?

a. List
b. Map
c. Set
d. SortedSet
e. SortedMap
f. None of the above

Question 13

import java.util.*;
class GFC111 {
  public static void main (String[] args) {
    Object m = new LinkedHashMap();
    System.out.print((m instanceof Collection)+",");
    System.out.print((m instanceof Map)+",");
    System.out.print(m instanceof HashMap);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 14

import java.util.*;
class GFC112 {
  public static void main (String[] args) {
    Object m = new LinkedHashSet();
    System.out.print((m instanceof Collection)+",");
    System.out.print((m instanceof Set)+",");
    System.out.print(m instanceof List);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 15

import java.util.*;
class GFC109 {
  public static void main (String[] args) {
    Object v = new Vector();
    System.out.print((v instanceof Collections)+",");
    System.out.print((v instanceof Arrays)+",");
    System.out.print(v instanceof List);
}}

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

a. Prints: false,false,false
b. Prints: false,false,true
c. Prints: false,true,false
d. Prints: false,true,true
e. Prints: true,false,false
f. Prints: true,false,true
g. Prints: true,true,false
h. Prints: true,true,true
i. None of the above

Question 16

 •Stores key/value pairs.
 •Allows null elements, keys, and values.
 •Duplicate entries replace old entries.
 •Entries are not sorted using a Comparator or the Comparable interface.
 •The iteration order is unspecified.

Which of these classes provides the specified features?

a. LinkedList
b. LinkedHashMap
c. LinkedHashSet
d. TreeMap
e. TreeSet
f. HashMap
g. HashSet
h. Hashtable
i. None of the above

Question 17

 •Stores key/value pairs.
 •Does not allow null elements, keys, and values.

Which of these classes provides the specified features?

a. LinkedList
b. LinkedHashMap
c. LinkedHashSet
d. TreeMap
e. TreeSet
f. HashMap
g. HashSet
h. Hashtable
i. None of the above
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