OCJP Study 22

OCJP(Java 6) 기출문제 연습 22(211~220)

PC나 스마트폰에서도 동일하게 실행되므로 장소를 가리지 않고 OCJP(JAVA 6) 국제 자격증을 목표로 학습할 수 있다.

QUESTION 211
Given that:
Gadget has-a Sprocket and Gadget has-a Spring and Gadget is-a Widget and Widget has-a Sprocket
Which two code fragments represent these relationships? (Choose two.)

A. class Widget {
Sprocket s;
}
class Gadget extends Widget {
Spring s;
}
B. class Widget {
}
class Gadget extends Widget {
Spring s1;
Sprocket s2;
}
C. class Widget {
Sprocket s1;
Spring s2;
}
class Gadget extends Widget {
}
D. class Gadget {
Spring s;
}
class Widget extends Gadget {
Sprocket s;
}
E. class Gadget {
}
class Widget extends Gadget {
Sprocket s1;
Spring s2;
}
F. class Gadget {
Spring s1;
Sprocket s2;
}
class Widget extends Gadget {
}

A,C

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QUESTION 212 Given:
class Pizza {
java.util.ArrayList toppings;
public final void addTopping(String topping) {
toppings.add(topping);
}
public void removeTopping(String topping) {
toppings.remove(topping);
}
}
public class PepperoniPizza extends Pizza {
public void addTopping(String topping) {
System.out.println("Cannot add Toppings");
}
public static void main(String[] args) {
Pizza pizza = new PepperoniPizza();
pizza.addTopping("Mushrooms");
pizza.removeTopping("Peperoni");
}
}
What is the result?

A. Compilation fails.
B. Cannot add Toppings
C. The code runs with no output.
D. A NullPointerException is thrown in Line 4.

A

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QUESTION 213
Given:
class Pizza {
java.util.ArrayList toppings;
public final void addTopping(String topping) {
toppings.add(topping);
}
public void removeTopping(String topping) {
toppings.remove(topping);
}
}
public class PepperoniPizza extends Pizza {
public void addTopping(String topping) {
System.out.println("Cannot add Toppings");
}
public static void main(String[] args) {
Pizza pizza = new PepperoniPizza();
pizza.addTopping("Mushrooms");
pizza.removeTopping("Peperoni");
}
}
What is the result?

A. Compilation fails.
B. Cannot add Toppings
C. The code runs with no output.
D. A NullPointerException is thrown in Line 4.

A

Error msg: "Cannot override the final method from Pizza" on the line "public void addTopping (String topping) {" from the class PepperoniPizza
ZZZ

QUESTION 214
Which three statements are true? (Choose three.)

A. A final method in class X can be abstract if and only if X is abstract.
B. A protected method in class X can be overridden by any subclass of X.
C. A private static method can be called only within other static methods in class X.
D. A non-static public final method in class X can be overridden in any subclass of X.
E. A public static method in class X can be called by a subclass of X without explicitly referencing the class X.
F. A method with the same signature as a private final method in class X can be implemented in a subclass of X.
G. A protected method in class X can be overridden by a subclass of X only if the subclass is in the same package as X.

B,E,F

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QUESTION 215 Click the Exhibit button.
1. public class Car {
2. private int wheelCount;
3. private String vin;
4. public Car(String vin){
5. this.vin = vin;
6. this.wheelCount = 4;
7. }
8. public String drive(){
9. return "zoom-zoom";
10. }
11. public String getInfo() {
12. return "VIN: " + vin + " wheels: " + wheelCount;
13. }
14.}
And
1. public class MeGo extends Car {
2. public MeGo(String vin) {
3. this.wheelCount = 3;
4. }
5. }
What two must the programmer do to correct the compilation errors? (Choose two.)

A. insert a call to this() in the Car constructor
B. insert a call to this() in the MeGo constructor
C. insert a call to super() in the MeGo constructor
D. insert a call to super(vin) in the MeGo constructor
E. change the wheelCount variable in Car to protected
F. change line 3 in the MeGo class to super.wheelCount = 3;

D,E

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QUESTION 216
Click the Exhibit button.
1. import java.util.*;
2. public class TestSet{
3. enum Example {ONE, TWO, THREE }
4. public static void main(String[] args) {
5. Collection coll = new ArrayList();
6. coll.add(Example.THREE);
7. coll.add(Example.THREE);
8. coll.add(Example.THREE);
9. coll.add(Example.TWO);
10. coll.add(Example.TWO);
11. coll.add(Example.ONE);
12. Set set = new HashSet(coll);
13. }
14.}
Which statement is true about the set variable on line 12?

A. The set variable contains all six elements from the coll collection, and the order is guaranteed to be preserved.
B. The set variable contains only three elements from the coll collection, and the order is guaranteed to be preserved.
C. The set variable contains all six elements from the coll collection, but the order is NOT guaranteed to be preserved.
D. The set variable contains only three elements from the coll collection, but the order is NOT guaranteed to be preserved.

D

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QUESTION 217
Given:
public class Person {
private String name, comment;
private int age;
public Person(String n, int a, String c) {
name = n;
age = a;
comment = c;
}
public boolean equals(Object o) {
if (!(o instanceof Person))
return false;
Person p = (Person) o;
return age == p.age && name.equals(p.name);
}
}
What is the appropriate definition of the hashCode method in class Person?

A. return super.hashCode();
B. return name.hashCode() + age * 7;
C. return name.hashCode() + comment.hashCode() / 2;
D. return name.hashCode() + comment.hashCode() / 2 - age * 3;

B

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QUESTION 218
Given:
public class Key {
private long id1;
private long id2;
// class Key methods
}
A programmer is developing a class Key, that will be used as a key in a standard java.util.HashMap.
Which two methods should be overridden to assure that Key works correctly as a key? (Choose two.)

A. public int hashCode()
B. public boolean equals(Key k)
C. public int compareTo(Object o)
D. public boolean equals(Object o)
E. public boolean compareTo(Key k)

A,D

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QUESTION 219
Given:
import java.util.*;
public class Hancock {
// insert code here Linea 5
list.add("foo");
}
}
Which two code fragments, inserted independently at line 5, will compile without warnings? (Choose two.)

A. public void addStrings(List list) {
B. public void addStrings(List<string> list) {
C. public void addStrings(List<!--? super String--> list) {
D. public void addStrings(List<!--? extends String--> list) {

B,C

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QUESTION 220
A programmer has an algorithm that requires a java.util.List that provides an efficient implementation of add (0, object), but does NOT need to support quick random access.
What supports these requirements?

A. java.util.Queue
B. java.util.ArrayList
C. java.util.LinearList
D. java.util.LinkedList

D

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