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多项选择题

Which are true (Choose all that apply.)

A．If class A is-a class B, then class A cannot be considered well encapsulated.
B．If class A has-a class B, then class A cannot be considered well encapsulated.
C．If class A is-a class B, then the two classes are said to be cohesive.
D．If class A has-a class B, then the two classes are said to be cohesive.
E．If class A is-a class B, it"s possible for them to still be loosely coupled.
F．If class A has-a class B, it"s possible for them to still be loosely coupled.
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你可能感兴趣的试题

多项选择题

Given:
3. class Department {
4. Department getDeptName() {return new Department(); }
5. }
6. class Accounting extends Department {
7. Accounting getDeptName() {return new Accounting(); }
8. // insert code here
13. }
And the following four code fragments:
Ⅰ. String getDeptName(int x) {return "mktg"; }
Ⅱ. void getDeptName(Department d) { ; }
Ⅲ. void getDeptName(long x) throws NullPointerException {
throw new NullPointerException();
}
Ⅳ. Department getDeptName() throws NullPointerException {
throw new NullPointerException();
return new Department();
}
Which are true (Choose all that apply.)

A．If fragment Ⅰ is inserted at line 8, the code compiles.
B．If fragment Ⅱ is inserted at line 8, the code compiles.
C．If fragment Ⅲ is inserted at line 8, the code compiles.
D．If fragment Ⅳ is inserted at line 8, the code compiles.
E．If none of the fragments are inserted at line 8, the code compiles.
单项选择题

Given:
2. import java.util.*;
3. interface Canine { }
4. class Dog implements Canine { }
5. public class Collie extends Dog {
6. public static void main(String[] args) {
7. List＜Dog＞ d = new ArrayList＜Dog＞();
8. List＜Collie＞ c = new ArrayList＜Collie＞();
9. d. add (new Collie());
10. c. add (new Collie());
11. do1(d); do1(c);
12. do2(d); do2(c);
13. }
14. static void dol (List＜ extends Dog＞ d2) {
15. d2.add(new Collie());
16. System.out.print(d2.size());
17. }
18. static void do2(List＜ extends Canine＞ c2) { }
19. }
Which are true (Choose all that apply.)

A．Compilation succeeds.
B．Compilation fails due to an error on line 9.
C．Compilation fails due to an error on line 14.
D．Compilation fails due to an error on line 15.
E．Compilation fails due to an error on line 16.
F．Compilation fails due to an error on line 18.
G．Compilation fails due to errors on lines 11 and 12.
单项选择题

Given:
2. class Robot { }
3. interface Animal { }
4. class Feline implements Animal { }
5. public class BarnCat extends Feline {
6. public static void main(String[] args) {
7. Animal af = new Feline();
8. Feline ff = new Feline();
9. BarnCat b = new BarnCat();
10. Robot r = new Robot();
11. if(af instanceof Animal) System.out.print("1 ");
12. if(af instanceof BarnCat) System.out.print("2 ");
13. if(b instanceof Animal) System.out.print("3 ");
14. if(ff instanceof BarnCat) System.out.print ("4 ");
15. if(r instanceof Animal) System.out .print ("5 ");
16. }
17. }
What is the result

A．1
B．1 3
C．1 2 3
D．1 3 4
E．1 2 3 4
F．Compilation fails.
G．An exception is thrown at runtime.
多项选择题

Which are true (Choose all that apply.)

A．If class A is-a class B, then class A cannot be considered well encapsulated.
B．If class A has-a class B, then class A cannot be considered well encapsulated.
C．If class A is-a class B, then the two classes are said to be cohesive.
D．If class A has-a class B, then the two classes are said to be cohesive.
E．If class A is-a class B, it"s possible for them to still be loosely coupled.
F．If class A has-a class B, it"s possible for them to still be loosely coupled.
单项选择题

Given that FileNotFoundException extends IOException and given:
2. import java.io.*;
3. public class Changeup {
4. public static void main(String[] args) throws IOException {
5. new Changeup() .go();
6. new Changeup() .go2();
7. new Changeup() .go3();
8. }
9. void go() {throw new IllegalArgumentException(); }
10.
11. void go2() throws FileNotFoundException { }
12.
13. void go3() {
14. try {throw new Exception(); }
15. catch (Throwable th) {throw new NullPointerException(); }
16. } }
What is the result (Choose all that apply.)

A．An IOException is thrown at runtime.
B．A NullPointerException is thrown at runtime.
C．An IllegalArgumentException is thrown at runtime.
D．Compilation fails due to an error at line 4.
E．Compilation fails due to an error at line 9.
F．Compilation fails due to an error at line 11.
G．Compilation fails due to an error at line 15.
单项选择题

Given:
2. public class Sunny extends Weather {
3. public static void main(String[] args) {
4. try {
5. new Sunny() .do1();
6. new Sunny() .do2();
7. new Sunny() .do3();
8. }
9. catch(Throwable t) {System.out.print("exc "); }
10. } }
11. class Weather {
12. void do1() {System.out.print("do1 "); }
13. private void do2() {System.out.print("do2 "); }
14. protected void do3() {System.out.print("do3 "); }
15. }
What is the result

A．do1 exc
B．do1 do2 exc
C．do1 do2 do3
D．Compilation fails.
E．An exception is thrown at runtime.
单项选择题

Given:
42. void go() {
43. int cows = 0;
44. int[] twisters = {1,2,3};
45. for(int i = 0; i ＜ 4; i++)
46. switch(twisters[i]) {
47. case 2: cows++;
48. case 1: cows += 10;
49. case 0: go();
50. }
51. System.out.println(cows);
52. }
What is the result

A．11
B．21
C．22
D．Compilation fails.
E．A StackOverflowError is thrown at runtime.
F．An ArraylndexOutOfBoundsException is thrown at runtime.
单项选择题

Given:
2. import java.util.*;
3. public class Volleyball {
4. public static void main(String[] args) {
5. TreeSet＜String＞ s = new TreeSet＜String＞();
6. s.add("a"); s.add("f"); s.add("b");
7. System.out.print(s + " ");
8. Collections.reverse(s);
9. System.out.println(s);
10. } }
What is the result

A．Compilation fails.
B．[a, b, f] [a, b, f]
C．[a, b, f] [f, b, a]
D．[a, f, b] [b, f, a]
E．[a, b, f], followed by an exception.
F．[a, f, b], followed by an exception.
单项选择题

Given:
3. import java.io.*;
4. public class Kesey {
5. public static void main(String[] args) throws Exception {
6. File file = new File("bigData.txt");
7. FileWriter w = new FileWriter(file);
8. w.println("lots o" data");
9. w.flush();
10. w.close();
11. } }
What is the result (Choose all that apply.)

A．An empty file named "bigData.txt" is created.
B．Compilation fails due only to an error on line 5.
C．Compilation fails due only to an error on line 6.
D．Compilation fails due only to an error on line 7.
E．Compilation fails due only to an error on line 8.
F．Compilation fails due to errors on multiple lines.
G．A file named "bigData.txt" is created, containing one line of data.
单项选择题

Given:
2. public class Boggy {
3. final static int mine = 7;
4. final static Integer i = 57;
5. public static void main(String[] args) {
6. int x : go(mine);
7. System.out.print(mine + " " + x + " ");
8. x += mine;
9. Integer i2 = i;
10. i2 = go(i);
11. System.out.println(x + " " + i2);
12. i2 = new Integer(60);
13. }
14. static int go(int x) {return ++x; }
15. }
What is the result

A．7 7 14 57
B．7 8 14 57
C．7 8 15 57
D．7 8 15 58
E．7 8 16 58
F．Compilation fails.
G．An exception is thrown at runtime.
单项选择题

Given:
3. class Wanderer implements Runnable {
4. public void run() {
5. for(int i = 0; i ＜ 2; i++)
6. System.out.print(Thread.currentThread() .getName() + " ");
7. } }
8. public class Wander {
9. public static void main(String[] args) {
10. Wanderer w = new Wanderer();
11. Thread t1 = new Thread();
12. Thread t2 = new Thread(w);
13. Thread t3 = new Thread(w, "fred");
14. t1.start(); t2.start(); t3.start();
15. } }
Which are true (Choose all that apply.)

A．Compilation fails.
B．No output is produced.
C．The output could be Thread- 1 fred fred Thread- 1
D．The output could be Thread-1 Thread-1 Thread-2 Thread-2
E．The output could be Thread-1 fred Thread-1 Thread-2 Thread-2 fred
F．The output could be Thread-1 Thread-1 Thread-2 Thread-3 fred fred
单项选择题

Given:
2. import java.util.*;
3. public class MyFriends {
4. String name;
5. MyFriends(String s) {name = s; }
6. public static void main(String[] args) {
7. Set＜MyFriends＞ ms = new HashSet＜MyFriends＞();
8. ms.add(new MyFriends("Bob"));
9. System.out.print(ms + " ");
10. ms.add(new MyFriends("Bob"));
11. System.out.print(ms + " ");
12. ms.add(new MyFriends("Eden"));
13. System.out.print(ms + " ");
14. }
15. public String toString() {return name; }
16. }
What is the most likely result

A．Compilation fails.
B．[Bob] [Bob] [Eden, Bob]
C．[Bob] [Bob] [Eden, Bob, Bob]
D．[Bob], followed by an exception.
E．[Bob] [Bob, Bob] [Eden, Bob, Bob]
单项选择题

Given the proper imports, and given:
17. public void go() {
18. NumberFormat nf, nf2;
19. Number n;
20. Locale[] la = NumberFormat.getAvailableLocales();
21. for(int x=0; x ＜ 10; x++) {
22. nf = NumberFormat.getCurrencyInstance(la[x]);
23. System.out.println(nf.format(123.456f));
24. }
25. nf2 = NumberFormat.getInstance();
26. n = nf2.parse("123.456f");
27. System.out.println(n);
28. }
Given that line 20 is legal, which are true (Choose all that apply.)

A．Compilation fails.
B．An exception is thrown at runtime.
C．The output could contain "123.46"
D．The output could contain "123.456"
E．The output could contain "$123.46"
单项选择题

Given:
59. Integer i1 = 2001; // set 1
60. Integer i2 = 2001;
61. System.out.println((i1 == i2) + " " + i1.equals(i2)); // output 1
62. Integer i3 = 21; // set 2
63. Integer i4 = new Integer(21);
64. System.out.println((i3 == i4) + " " + i3.equals(i4)); // output 2
65. Integer i5 = 21; // set 3
66. Integer i6 = 21;
67. System.out.println((i5 == i6) + " " + i5.equals(i6)); // output 3
What is the result (Choose all that apply.)

A．Compilation fails.
B．An exception is thrown at runtime.
C．All three sets of output will be the same.
D．The last two sets of output will be the same.
E．The first two sets of output will be the same.
F．The first and last sets of output will be the same.
多项选择题

Given:
1. import java.util.*;
2. public class Piles {
3. public static void main (String[] args) {
4. TreeMap＜String, String＞ tm = new TreeMap＜String, String＞();
5. TreeSet＜String＞ ts = new TreeSet＜String＞();
6. String[] k = {"1", "b", "4", "3"};
7. String[] v = {"a", "d", "3", "b"};
8. for(int i=0; i＜4; i++) {
9. tm.put (k[i], v[i]);
10. ts.add(v[i]);
11. }
12. System.out.print(tm.values() + " ");
13. Iterator it2 = ts.iterator();
14. while(it2.hasNext()) System.out.print(it2.next() + "-");
15. } }
Which of the following could be a part of the output (Choose two.)
A. [a, b, 3, d]
B. [d, a, b, 3]
C. [3, a, b, d]
D. [a, b, d, 3]
E. [1, 3, 4,b]
F. [b, 1,3,4]
G. 3-a-b-d-
H. a-b-d-3-
I. a-d-3-b-

单项选择题

Given:
2. public class Skip {
3. public static void main(String[] args) throws Exception {
4. Thread t1 = new Thread(new Jump());
5. Thread t2 = new Thread(new Jump());
6. t1.start(); t2.start();
7. t1.join(500);
8. new Jump() .run();
9. } }
10. class Jump implements Runnable {
11. public void run() {
12. for(int i = 0; i ＜ 5; i++) {
13. try {Thread.sleep(200); }
14. catch (Exception e) {System.out.print("e "); }
15. System.out.print(Thread.currentThread() .getId() + "-" + i+ " ");
16. } } }
What is the result

A．Compilation fails.
B．The main thread will run mostly before t1 runs.
C．The main thread will run after t1, but together with t2.
D．The main thread will run after t2, but together with t1.
E．The main thread will run after both t1 and t2 are mostly done.
F．The main thread"s execution will overlap with t1 and t2"s execution.
多项选择题

Given this code in a method:
5. String s = "dogs. with words.";
6. // insert code here
7. for(String o: output)
8. System.out.print(o + " ");
Which of the following, inserted independently at line 6, will produce output that contains the String "dogs" (Choose all that apply.)

A．String[] output = s.split("s");
B．String[] output = s.split("d");
C．String[] output = s.split("\\d");
D．String[] output = s.split("\\s");
E．String[] output = s.split("\\w");
F．String[] output = s.split("\\.");
多项选择题

Given:
1. import java.util.*;
2. enum Heroes {GANDALF, HANS, ENDER}
3. public class MyStuff {
4. public static void main(String[] args) {
5. List＜String＞ stuff = new ArrayList＜String＞();
6. stuff.add("Bob"); stuff.add("Fred");
7. new MyStuff().go();
8. }
9. Heroes myH = Heroes.ENDER;
10. void go() {
11. for(Heroes h: Heroes.values())
12. if(h == myH) System.out.println(myH);
13. } }
Which are true (Choose all that apply.)

A．Compilation fails.
B．main() has-a List
C．MyStuffhas-a List
D．MyStuff has-a Heroes
E．The output is "ENDER"
F．The output is "Heroes.ENDER"
G．An exception is thrown at runtime.
单项选择题

Given the design implied by this partially implemented class:
2. public class RobotDog {
3. int size;
4. void bark() { /* do barking */ }
5. int getSize() {return size; }
6. {size = 16; }
7. int getNetworkPrinterID() {
8. /* do lookup */
9. return 37;
10. }
11. voidprintRobotDogStuff(intprinterID) { /*print RobotDog stuff*/ }
12. }
Which are true (Choose all that apply.)

A．Compilation fails.
B．To improve cohesion, the size variable should be declared private.
C．To improve cohesion, the initialization block should be placed inside a constructor.
D．To improve cohesion, printRobotDogStuff() should be moved to a different class.
E．To improve cohesion, getNetworkPrinterlD0 should be moved to a different class.
单项选择题

Given:
2. import java.util.*;
3. public class Foggy extends Murky {
4. public static void main(String[] args) {
5. final List＜String＞ s = new ArrayList＜String＞();
6. s.add("a"); s.add("f"); s.add("a");
7. new Foggy() .mutate(s);
8. System.out.println(s);
9. }
10. List＜String＞ mutate (List＜String＞ s) {
11. List＜String＞ ms = s;
12. ms.add ("c");
13. return s;
14. }
15. }
16. class Murky {
17. final void mutate(Set s) { }
18. }
What is the most likely result

A．[a,f]
B．[a, f, a]
C．[a, f, c]
D．[a, f, a, c]
E．Compilation fails.
F．An exception is thrown at runtime.
多项选择题

Given:
2. public class Pregnant extends Thread {
3. int x = 0;
4. public static void main(String[] args) {
5. Runnable r1 = new Pregnant();
6. new Thread(r1) .start();
7. new Thread(r1) .start();
8. }
9. public void run() {
10. for(int j = 0; j ＜ 3; j++) {
11. x = x + 1;
12. x = x + 10;
13. System.out.println(x + " ");
14. x = x + 100;
15. } } }
If the code compiles, which value(s) could appear in the output (Choose all that apply.)

A．12
B．22
C．122
D．233
E．244
F．566
G．Compilation fails.
多项选择题

Given:
2. public class Toolbox {
3. static Toolbox st;
4. public static void main(String[] args) {
5. new Toolbox().go();
6. // what"s eligible
7. }
8. void go() {
9. MyInner in = new MyInner();
10. Integer i3 = in.doInner();
11. Toolbox t = new Toolbox();
12. st = t;
13. System.out.println(i3);
14. }
15. class MyInner {
16. public Integer doInner() {return new Integer(34);
17. }
18. }
When the code reaches line 6, which are eligible for garbage collection (Choose all that apply.)

A．st
B．in
C．.i3
D．The object created on line 5.
E．The object created on line 9.
F．The object created on line 10.
G．The object created on line 11.
单项选择题

Given:
2. class Ball {
3. static String s = "";
4. void doStuff() {s += "bounce "; }
5. }
6. class Basketball extends Ball {
7. void doStuff() {s += "swish "; }
8. }
9. public class Golfball extends Ball {
10. public static void main(String[] args) {
11. Ball b = new Golfball();
12. Basketball bb = (Basketball)b;
13. b.doStuff();
14. bb.doStuff();
15. System.out.println(s);
16. }
17. void doStuff() {s += "fore "; }
18. }
What is the result

A．fore fore
B．fore swish
C．bounce swish
D．bounce bounce
E．Compilation fails.
F．An exception is thrown at runtime.
多项选择题

Given the following three files:
2. package apollo;
3. import apollo.modules.Lunar;
4. public class Saturn {
5. public static void main(String[] args) {
6. Lunar lunarModule = new Lunar();
7. System.out.println(lunarModule);
8. } }
2. package apollo.modules;
3. public interface Module { /* more code */ }
2. package apollo.modules;
3. public class Lunar implements Module { /* more code */ }
And given that Module.java and Lunar.java were successfully compiled and the directory structureisshownbelow:
$ROOT
|-- apollo
| |-- modules
| |-- Lunar.class
|-- controls.jar
| |-- apollo
| |-- modules
| |-- Module. class
|-- Saturn. java

Which are correct about compiling and running the Saturn class from the $ROOT directory (Choose all that apply.)

A．The command for compiling is javac -d. -cp. Saturn.java
B．The command for compiling is javac -d. -cp controls.jar Saturn.java
C．The command for compiling is javac -d. -cp .:controls.jar Saturn.java
D．The command for running is java -cp. apollo.Saturn
E．The command for running is java -cp controls.jar apollo.Saturn
F．The command for running is java -cp .:controls.jar apollo.Saturn
G．The command for running is java -cp controls.jar -cp. apollo.Saturn
多项选择题

Given:
5. class OOthing {void doStuff() {System.out.print("oo "); } }
6. class GuiThing extends OOthing {
7. void doStuff() {System.out.print("gui "); }
8. }
9. public class Button extends GuiThing {
10. void doStuff() {System.out.print("button "); }
11. public static void main(String[] args) {new Button().go();}
12. void go() {
13. GuiThing g = new GuiThing();
14. // this.doStuff();
15. // super.doStuff();
16. // g.super.doStuff();
17. // super.g.doStuff();
18. // super.super.doStuff();
19. } }
If the commented lines are uncommented independently, which are true (Choose all that apply.)

A．If line 14 is uncommented, "button" will be in the output.
B．If line 15 is uncommented, "gui" will be in the output.
C．If line 16 is uncommented, "oo" will be in the output.
D．If line 17 is uncommented, "oo" will be in the output.
E．If line 18 is uncommented, "oo" will be in the output.
单项选择题

Given:
2. import java.util.*;
3. public class Salt {
4. public static void main(String[] args) {
5. Set s1 = new HashSet();
6. s1.add(0);
7. s1.add("1");
8. doStuff(s1);
9. }
10. static void doStuff(Set＜Number＞ s) {
11. do2(s);
12. Iterator i = s.iterator();
13. while(i.hasNext()) System.out.print(i.next() + " ");
14. Object[] oa = s.toArray();
15. for(int x = 0; x ＜ oa.length; x++)
16. System.out.print(oa[x] + " ");
17. System.out.println(s.contains(1));
18. }
19. static void do2(Set s2) {System.out.print(s2.size() + " ");
20. }
What is the most likely result

A．2 0 1 0 1 true
B．2 0 1 0 1 false
C．Compilation fails.
D．An exception is thrown at line 8.
E．An exception is thrown at line 13.
F．An exception is thrown at line 14.
G．An exception is thrown at line 19.
单项选择题

Given:
1. public class Begin {
2. static int x;
3. {int[] ia2 = {4,5,6};
4. static {
5. int[] ia = {1,2,3};
6. for(int i = 0; i ＜ 3; i++)
7. System.out.print(ia[i] + " ");
8. x= 7;
9. System.out.print(x + " ");
10. } }
And, if the code compiles, the invocation:
java Begin
What is the result

A．Compilation fails.
B．"1 2 3 7", with no exception thrown.
C．"1 2 3 7", followed by an exception.
D．"1 2 3", followed by an ExceptionlnlnitializerError.
E．ExceptionlnlnitializerError is thrown before any output.
F．Some other exception is thrown before any other output.
单项选择题

Given:
1. abstract class Vibrate {
2. static String s = "-";
3. Vibrate() {s += "v"; }
4. }
5. public class Echo extends Vibrate {
6. Echo() {this(7); s += "e"; }
7. Echo(int x) {s += "e2"; }
8. public static void main(String[] args) {
9. System.out.print("made " + s + " ");
10. }
11. static {
12. Echo e = new Echo();
13. System.out.print("block " + s + " ");
14. } }
What is the result

A．made-ve2e
B．block-ee2v
C．block-ve2e
D．made-eve2 block-eve2
E．made-ve2e block-ve2e
F．block-ve2emade-ve2e
G．block-ve2emade-ve2eve2e
H．Compilation fails
单项选择题

Given:
2. public class Alamo {
3. public static void main(String[] args) {
4. try {
5. assert(!args[0] .equals("x")) : "kate";
6. } catch(Error e) {System.out.print("ae "); }
7. finally {
8. try {
9. assert(!args[0] .equals("y")) : "jane";
10. } catch(Exception e2) {System.out.print("ae2 ");
11. finally {
12. throw new IllegalArgumentException();
13. } } } }
And, if the code compiles, the invocation:
java -ea Alamo y
Which will be included in the output (Choose all that apply.)

A．ae
B．ae2
C．kate
D．jane
E．AssertionError
F．IllegalArgumentException
G．There is no output because compilation fails.
单项选择题

Given:
3. public class KaChung {
4. public static void main(String[] args) {
5. String s = "";
6. if(Integer.parseInt("011") == Integer.parseInt("9")) s += 1;
7. if(021 == Integer.valueOf("17")) s += 2;
8. if(1024 == new Integer(1024)) s += 3;
9. System.out.println(s);
10. } }
What is the result

A．2
B．3
C．13
D．23
E．123
F．Compilation fails.
G．An exception is thrown at runtime.
单项选择题

Given:
3. import java.util.*;
4. public class VC {
5. public static void main(String[] args) {
6. List＜Integer＞ x = new ArrayList＜Integer＞();
7. Integer[] a = {3, 1, 4, 1};
8. x = Arrays.asList(a);
9. a[3] = 2;
10. x.set(0, 7);
11. for(Integer i: x) System.out.print(i + " ");
12. x.add(9);
13. System.out.println(x);
14. } }
What is the result

A．Compilation fails.
B．3 1 4 2[7,1,4,1]
C．3 1 4 2[7,1,4,2]
D．7 1 4 2[7,1,4,2]
E．3 1 4 2[7,1,4,1,9]
F．3 1 4 2[7,1,4,2,9]
G．7 1 4 2, followed by an exception.
H．3 1 4 2, followed by an exception.
单项选择题

Given:
3. public class Honcho {
4. static boolean b1 = false;
5. static int z = 7;
6. static Long y;
7. public static void main(String[] args)
8. for(int i = 0; i ＜ 4; i++)
9. go(i);
10. }
11. static void go(int x) {
12. try {
13. if((x == 0) && (!b1 && z == 7)) System.out.print("0 ");
14. if(x ＜ 2 ^ x ＜ 10) System.out.print("1 ");
15. if((x == 2) &&
(y == null | (y.longValue() == 0))) System.out.print("2 ");
16. if(z ＜= (x + 4)) System.out.print("3 ");
17. }
18. catch (Exception e) {System.out.print("e "); }
19. } }
What is the result

A．0 1 2 3
B．1 e 1 3
C．0 1 e 1 3
D．0 1 1 1 1 3
E．1 1 1 2 1 3
F．0 1 1 1 2 1 3
G．Compilation fails.
多项选择题

Given:
2. class Chilis {
3. Chilis(String c, int h) {color = c; hotness = h; }
4. String color;
5. int hotness;
6. public boolean equals(Object o) {
7. Chilis c = (Chilis)o;
8. if(this.color == c.color) return true;
9. return false;
10. }
11. public int hashCode() {return (color.length() + hotness);
12. }
If instances of class Chilis are to be used as keys in a Map, which are true(Choose all that apply.)

A．The code will not compile.
B．The hashCode() and equals() contracts have been supported.
C．The equals() method is reflexive, symmetric, and transitive.
D．The Chilis class CANNOT be used to create keys to reliably add and retrieve entries in a Map.
E．If the hashCode() method is not considered, the equals() method could be an override that supports the equals() contract.
F．If the equals() method is not considered, the hashCode() method could be an override that supports the hashCode() contract.
多项选择题

Given:
2. package pack.clients;
3. import pack.banking. Bank;
4. public class Client{
5. public static void main(String[] args) {
6. Bank bank = new Bank();
7. System.out.println(bank.getMoney(2000L));
8. } }
And given that Client.java resides in the $ROOT directory and is not yet compiled. There is another class named pack.banking.Bank, which has a method called getMoney(long) that returns a value. Bank class is compiled and deployed into a JAR file called pack.jar, as shown in the following directory structure
$ROOT
|-- Client.java
|-- [pack.jar]
|-- pack
|-- banking
|-- Bank.class
Which are correct about compiling or running the Client class from the $ROOT directory (Choose all that apply.)

A．To compile, use javac -cp pack.jar -d. Client.java
B．To compile, use javac -cp pack.jar#pack.banking.Bank-d. Client.java
C．To compile, use javac -cp * -d. Client.java
D．To run, use java -cp pack.jar pack.clients.Client
E．To run, use java -cp. -d pack.jar pack.clients.Client
F．To run, use java -cp. -cp pack.jar pack.clients.Client
G．To run, use java -cp .:pack.jar pack.clients.Client
单项选择题

Given:
2. class Bird {
3. public static String s = "";
4. public static void fly() {s += "fly "; }
5. }
6. public class Hummingbird extends Bird {
7. public static void fly() {s += "hover "; }
8. public static void main(String[] args) {
9. Bird b1 = new Bird();
10. Bird b2 = new Hummingbird();
11. Bird b3 = (Hummingbird)b2;
12. Hummingbird b4 = (Hummingbird)b2;
13.
14. b1.fly(); b2.fly(); b3.fly(); b4.fly();
15. System.out.println(s);
16. } }
What is the result

A．fly fly fly fly
B．fly fly fly hover
C．fly fly hover hover
D．fly hover hover hover
E．hover hover hover hover
F．Compilation fails.
G．An exception is thrown at runtime.
多项选择题

Given two files:
1. package com;
2. public class Extramuros {
3. public static void howdy() {System.out.print("howdy "); }
4. public static final Extramuros ex = new Extramuros();
5. public int instVar = 42;
6. public enum avout {OROLO, JAD};
7. }
1. // insert code here
…
6. public class Theorics {
7. public static void main(String[] args) {
8. Extramuros.howdy();
9. System.out.print(Extramuros.avout.OROLO + " ");
10. howdy();
11. System.out.print(ex.instVar + " ");
12. }}
Which are the minimum line(s) of code to add at "insert code here" for the files to compile (Choose all that apply.)

A．import static com.*;
B．import com.Extramuros;
C．import com.Extramuros.*;
D．import static com.Extramuros;
E．import static com.Extramuros.*;
F．Even with correct imports, the code will not compile due to other errors.
多项选择题

Given:
2. import java.text.*;
3. import java.util.*;
4. public class Vogue {
5. public static void main(String[] args) {
6. DateFormat df1 = DateFormat.getInstance();
7. DateFormat df2 = DateFormat.getInstance(DateFormat. SHORT);
8. DateFormat df3 = DateFormat.getDateInstance(DateFormat. FULL);
9. DateFormat df4 = DateFormat.getDateInstance(DateFormat.EXTENDED);
10. } }
Which are true (Choose all that apply.)

A．Line 2 is not necessary.
B．Line 3 is not necessary.
C．Compilation fails due to an error on line 6.
D．Compilation fails due to an error on line 7.
E．Compilation fails due to an error on line 8.
F．Compilation fails due to an error on line 9.
多项选择题

Given:
2. public class Cult extends Thread {
3. static int count = 0;
4. public void run() {
5. for(int i = 0; i ＜ 100; i++) {
6. if(i == 5 && count ＜ 3) {
7. Thread t = new Cult(names[count++]);
8. t.start();
9. // insert code here
10. }
11. System.out.print(Thread.currentThread() .getName() + " ");
12. }
13. }
14. public static void main(String[] args) {
15. new Cult ("t0") .start();
16. }
17. Cult(String s) {super(s); }
18. String[] names = {"t1", "t2", "t3"};
19. }
And these two fragments:
Ⅰ. try {t.join(); } catch(Exception e) { }
Ⅱ. try {Thread.currentThread().join(); } catch(Exception e) { }
When each fragment is inserted independently at line 9, which are true (Choose all that apply.)

A．With fragment Ⅰ, t0 completes last.
B．With fragment Ⅰ, t3 completes last.
C．With fragment Ⅱ, t0 completes last.
D．With fragment Ⅱ, t3 completes last.
E．With both fragments, compilation fails.
F．With fragment Ⅰ, the code never completes.
G．With fragment Ⅱ, the code never completes.
多项选择题

Which are true (Choose all that apply.)

A．If a class"s member"s values can be retrieved, but not changed, without using the class"s API, the class is not cohesive.
B．If a class"s member"s values can be retrieved, but not changed, without using the class"s API, tight coupling could occur.
C．If a class"s member"s values can be retrieved, but not changed, without using the class"s API, the class is not well encapsulated.
D．If a class"s member"s values can be updated only through the use of its API, or by an inner class, the class is well encapsulated.
E．If a class"s member"s values can be updated only through the use of its API, or by an inner class, the class is NOT well encapsulated.
多项选择题

Given:
3. public class BigData {
4. static BigData bd;
5. public static void main(String[] args) {
6. new BigData().doStuff();
7. // do lots of memory intensive stuff
... // JVM finds an eligible BigData object for GC
... // JVM invokes finalize()
... // do more stuff
48. }
49. void doStuff() { }
50. // insert code here
51. bd = this;
52. }
53. }
54. class MyException extends Exception { }
and the following four fragments:
Ⅰ. protected void finalize() throws Throwable {
Ⅱ. protected void finalize() {
Ⅲ. protected void finalize() throws MyException {
Ⅳ. void finalize() {
If the fragments are inserted, independently, at line 50, which are true (Choose all that apply.)

A．Fragment Ⅰ compiles.
B．Fragment Ⅱ compiles.
C．Fragment Ⅲ compiles.
D．Fragment Ⅳ compiles.
E．Of those that compile, the GC will collect any given object after the JVM has called finalize() on that object.
F．Because of the way finalize() has been overridden, the GC will never collect eligible objects of type BigData.
多项选择题

Given:
2. interface Clickable {void click(); }
3. // insert code here
Which code, inserted independently at line 3, will compile (Choose all that apply.)

A．interface Keyboard extends Clickable { }
B．interface Keyboard extends Clickable {void click(); }
C．interface Keyboard extends Clickable {void doClick(); }
D．interface Keyboard extends Clickable {void click() { ; } }
E．interface Keyboard extends Clickable {protected void click(); }
F．interface Keyboard extends Clickable {void click(); void doClick(); }
多项选择题

Given:
1. public class Argue {
2. static boolean b;
3. static int x = 0;
4. public static void main(String[] args) {
5. int guess = (int) (Math.random() * 5);
6. if(guess ＜ 0) assert false;
7. assert b = true;
8. assert x = 0;
9. assert x == 0;
10. } }
Which are true (Choose all that apply.)

A．The code compiles.
B．The assert on line 6 is appropriate.
C．Compilation fails due to an error on line 6.
D．Compilation fails due to an error on line 7.
E．Compilation fails due to an error on line 8.
F．Compilation fails due to an error on line 9.
多项选择题

Given two files:
1. package com.wickedlysmart2;
2. public class Utils {
3. void do1() {System.out.print("do1 "); }
4. protected void do2() {System.out.print("do2 ");
5. public void do3() {System.out.print("do3 "); }
6. }
1. import com.wickedlysmart2.*;
2. public class UPS extends Utils {
3. public static void main(String[] args) {
4. Utils u = new Utils();
5. u.do1();
6. u.do2();
7. u.do3();
8. } }
What is the result (Choose all that apply.)

A．do1 do2 do3
B．"do1 ", followed by an exception.
C．Compilation fails due to an error on line 4 of UPS.
D．Compilation fails due to an error on line 5 of UPS.
E．Compilation fails due to an error on line 6 of UPS.
F．Compilation fails due to an error on line 7 of UPS.
单项选择题

Given the invocation "java GiveUp" and:
2. public class GiveUp {
3. public static void main(String[] args) throws Exception {
4. try {
5. assert false;
6. System.out.print("t ");
7. }
8. catch (Error e) {
9. System.out.print("c ");
10. throw new Exception();
11. }
12. finally {System.out.print("f "); }
13. } }
What is the result

A．.c
B．cf
C．tf
D．Compilation fails.
E．"c f" followed by an uncaught exception.
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