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多项选择题

Given:
2. class Animal { }
3. class Dog extends Animal { }
4. class Cat extends Animal { }
5. public class Mixer＜A extends Animal＞ {
6. public ＜C extends Cat＞ Mixer＜ super Dog＞ useMe(A a, C c) {
7. //Insert Code Here
8. } }
Which, inserted independently at line 7, compile (Choose all that apply.)

A．return null;
B．return new Mixer＜Dog＞();
C．return new Mixer＜Animal＞();
D．return new Mixer＜A＞();
E．return new Mixer＜a＞();
F．return new Mixer＜c＞();
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你可能感兴趣的试题

多项选择题

Given:
2. public class Payroll {
3. int salary;
4. int getSalary() {return salary; }
5. void setSalary(int s) {
6. assert(s ＞ 30000);
7. salary = s;
8. } }
Which are true (Choose all that apply.)

A．Compilation fails.
B．The class is well encapsulated as it stands.
C．Removing line 6 would weaken the class"s degree of cohesion.
D．Removing line 6 would weaken the class"s degree of encapsulation.
E．If the salary variable was private, the class would be well encapsulated.
F．Removing line 6 would make the class"s use of assertions more appropriate.
单项选择题

Given:
1. class GardenTool {
2. static String s = "";
3. String name = "Tool ";
4. GardenTooi(String arg) {this(); s += name;
5. GardenTool() {s += "gt "; }
6. }
7. public class Rake extends GardenTool {
8. {name = "Rake "; }
9. Rake(String arg) {s += name; }
10. public static void main(String[] args) {
11. new GardenTool("hey ");
12. new Rake("hi ");
13. System.out.println(s);
14. }
15. {name = "myRake "; }
16. }
What is the result

A．Tool Rake
B．Tool myRake
C．gt Tool Rake
D．gt Tool myRake
E．gt Tool gt Rake
F．gt Tool gt myRake
G．gt Tool gt Tool myRake
H．Compilation fails.
单项选择题

Given the proper import statement(s) and given:
4. Map＜String, String＞ h = new Hashtable＜String, String＞();
5. String[] k = {"1", "2", "3", null};
6. String[] v = {"a", "b", null, "d"};
7.
8. for(int i=0; i＜4; i++) {
9. h.put(k[i], v[i]);
10. System.out.print(h. get (k [i]) + " ");
11. }
12. System.out.print(h.size() + " " + h.values() + "\n");
What result is most likely

A．Compilation fails.
B．"a b d 3 [b, d, a]"
C．"a b null d 3 [b, d, a]"
D．"a b null d 4 [b, d, null, a]"
E．"a b", followed by an exception.
F．"a b null", followed by an exception.
多项选择题

Given:
3. public class Race {
4. public static void main(String[] args)
5. Horse h = new Horse();
6. Thread t1 = new Thread(h, "Andi");
7. Thread t2 = new Thread(h, "Eyra");
8. new Race() .go(t2);
9. t1.start();
10. t2.start();
11. }
12. void go(Thread t) {t.start(); }
13. }
14. class Horse implements Runnable {
15. public void run() {
16. System.out.print(Thread.currentThread() .getName() + " ");
17. } }
What is the result (Choose all that apply.)

A．Compilation fails.
B．No output is produced.
C．The output could be: "Andi Eyra"
D．The output could be: "Eyra Andi Eyra"
E．The output could be: "Eyra ", followed by an exception.
F．The output could be: "Eyra Andi ", followed by an exception.
多项选择题

Given:
3. public class Fiji {
4. static Fiji base;
5. Fiji f;
6. public static void main(String[] args) {
7. new Fiji() .go();
8. // do more stuff
9. }
10. void go() {
11. Fiji f1 = new Fiji();
12. base = f1;
13. Fiji f2 = new Fiji();
14. f1.f = f2;
15. Fiji f3 = f1.f;
16. f2.f = f1;
17. base = null; f1 = null; f2 = null;
18. // do stuff
19. } }
Which are true (Choose all that apply.)

A．At line 8, one object is eligible for garbage collection.
B．At line 8, two objects are eligible for garbage collection.
C．At line 8, three objects are eligible for garbage collection.
D．At line 18, 0 objects are eligible for garbage collection.
E．At line 18, two objects are eligible for garbage collection.
F．At line 18, three objects are eligible for garbage collection.
多项选择题

Your company makes compute-intensive, 3D rendering software for the movie industry. Your chief scientist has just discovered a new algorithm for several key methods in a commonly used utility class. The new algorithm will decrease processing time by 15 percent, without having to change any method signatures. After you change these key methods, and in the course of rigorous system testing, you discover that the changes have introduced no new bugs into the software.
In terms of your software"s overall design, which are probably true (Choose all that apply.)

A．Your software is well encapsulated.
B．Your software demonstrated low cohesion.
C．Your software demonstrated high cohesion.
D．Your software demonstrated loose coupling.
E．Your software demonstrated tight coupling.
多项选择题

Which are true about the classes and interfaces in j ava.util (Choose all that apply.)

A．LinkedHashSet is-a Collection.
B．Vector is-a List.
C．LinkedList is-a Queue.
D．LinkedHashMap is-a Collection.
E．TreeMap is-a SortedMap.
F．Queue is-a Collection.
G．Hashtable is-a Set.
单项选择题

Given:
2. class Grandfather {
3. static String name = "gf ";
4. String doStuff() {return "grandf "; }
5. }
6. class Father extends Grandfather {
7. static String name = "fa ";
8. String doStuff() {return "father "; }
9. }
10. public class Child extends Father {
11. static String name = "ch ";
12. String doStuff() {return "child "; }
13. public static void main(String[] args) {
14. Father f = new Father();
15. System.out.print(((Grandfather)f).name + ((Grandfather)f) .doStuff());
16. Child c = new Child();
17. System. out.println(((Grandfather) c) .name + ((Grandfather)c) .doStuff() + ((Father)c) .doStuff());
18. } }
What is the result (Choose all that apply.)

A．Compilation fails.
B．fa father ch child child
C．gf father gf child child
D．fa grandf ch grandf father
E．gf grandf gf grandf father
F．An exception is thrown at runtime.
多项选择题

Given:
1. class MyClass { }
And given that MyClass2 has properly overridden equals() and hashCode() objects from which classes make good hashing keys (Choose all that apply.)

A．MyClass
B．MyClass2
C．java.lang.String
D．java.lang.Integer
E．java.lang.StringBuilder
多项选择题

Given:
2. public class Buffalo {
3. static int x;
4. int y;
5. public static int getX() {return x; }
6. public static void setX(int newX) {x = newX; }
7. public int getY() {return y; }
8. public void setY(int newY) {y = newY; }
9. }
Which lines of code need to be changed to make the class thread safe (Choose all that apply.)

A．Line 2
B．Line 3
C．Line 4
D．Line 5
E．Line 6
F．Line 7
G．Line 8
多项选择题

Given:
2. class Animal { }
3. class Dog extends Animal { }
4. class Cat extends Animal { }
5. public class Mixer＜A extends Animal＞ {
6. public ＜C extends Cat＞ Mixer＜ super Dog＞ useMe(A a, C c) {
7. //Insert Code Here
8. } }
Which, inserted independently at line 7, compile (Choose all that apply.)

A．return null;
B．return new Mixer＜Dog＞();
C．return new Mixer＜Animal＞();
D．return new Mixer＜A＞();
E．return new Mixer＜a＞();
F．return new Mixer＜c＞();
多项选择题

Given:
2. class Chilis {
3. Chilis(String c, int h) {color = c; hotness = h; }
4. String color;
5. private int hotness;
6. public boolean equals(Object o) {
7. Chilis c = (Chilis)o;
8. if(color.equals(c.color) && (hotness == c.hotness)) return true;
9. return false;
10. }
11. // insert code here
12. }
Which, inserted independently at line 11, fulfill the equals() and hashCode() contract for Chilis (Choose all that apply.)

A．public int hashCode() {return 7; }
B．public int hashCode() {return hotness; }
C．public int hashCode() {return color.length(); }
D．public int hashCode() {return (int)(Math.random() * 200); }
E．public int hashCode() {return (color.length() + hotness); }
单项选择题

Given the proper import(s), and this code in a method:
4. List＜String＞ x = new LinkedList＜String＞();
5. Set＜String＞ hs = new HashSet＜String＞();
6. String[] v = {"a", "b", "c", "b", "a"};
7. for(String s: v) {
8. x.add(s); hs.add(s);
9. }
10. System.out.print(hs.size() + " " + x.size() + " ");
11. HashSet hs2 = new HashSet(x);
12. LinkedList x2 = new LinkedList(hs);
13. System.out.println(hs2.size() + " " + x2.size());
What is the result

A．3 3 3 3
B．3 5 3 3
C．3 5 3 5
D．5 5 3 3
E．5 5 5 5
F．Compilation fails.
G．An exception is thrown at runtime.
单项选择题

Given the proper import(s), and given:
4. public static void main(String[] args) {
5. List＜Integer＞ x = new ArrayList＜Integer＞();
6. x.add(new Integer(3));
7. doStuff (x);
8. for(Integer i: x)
9. System.out.print (i + " ");
10. }
11. static void doStuff(List y) {
12. y.add(new Integer(4));
13. y.add(new Float(3.14f));
14. }
What is the result (Choose all that apply.)

A．Compilation fails.
B．The output will be "4 "
C．The output will be "3 4"
D．The output will be "3 4 3.14"
E．The output will be "3 3.14 4 "
F．The output will be "3 4 ", followed by an exception.
G．An exception will be thrown before any output is produced.
单项选择题

Given:
3. class Bonds {
4. Bonds force() {return new Bonds(); }
5. }
6. public class Covalent extends Bonds {
7. Covalent force() {return new Covalent(); }
8. public static void main(String[] args) {
9. new Covalent() .go(new Covalent());
10. }
11. void go(Covalent c) {
12. go2(new Bonds() .force(), c.force());
13. }
14. void go2(Bonds b, Covalent c) {
15. Covalent c2 = (Covalent)b;
16. Bonds b2 = (Bonds)c;
17. } }
What is the result (Choose all that apply.)

A．A ClassCastException is thrown at line 15.
B．A ClassCastException is thrown at line 16.
C．Compilation fails due to an error on line 7.
D．Compilation fails due to an error on line 12.
E．Compilation fails due to an error on line 15.
F．Compilation fails due to an error on line 16.
单项选择题

Given:
1. import java.util.*;
2. public class Drawers {
3. public static void main(String[] args) {
4. List＜String＞ desk = new ArrayList＜String＞();
5. desk.add("pen"); desk.add("scissors"); desk.add("redStapler");
6. System.out.print(desk.indexOf("redStapler"));
7. Collection.reverse(desk);
8. System.out.print(" " + desk.indexOf("redStapler"));
9. Collection.sort(desk);
10. System.out.println(" " + desk.indexOf("redStapler"));
11. } }
What is the result

A．1 1 1
B．2 0 1
C．2 0 2
D．2 2 2
E．Compilation fails.
F．An exception is thrown at runtime.
单项选择题

Given:
1. import java.util. *;
2. class Radio {
3. String getFreq() {return "97.3"; }
4. static String getF() {return "97.3"; }
5. }
6. vclass Ham extends Radio {
7. String getFreq() {return "50.1"; }
8. static String getF() {return "50.1"; }
9. public static void main(String[] args) {
10. List＜Radio＞ radios = new ArrayList＜Radio＞();
11. radios.add(new Radio());
12. radios.add(new Ham());
13. for(Radio r: radios)
14. System.out.print(r.getFreq() + " " + r.getF() + " ");
15. } }
What is the result

A．50.1 50.1 50.1 50.1
B．50.1 97.3 50.1 97.3
C．97.3 50.1 50.1 50.1
D．97.3 97.3 50.1 50.1
E．97.3 97.3 50.1 97.3
F．97.3 97.3 97.3 97.3
G．Compilation fails.
H．An exception is thrown at runtime.
单项选择题

Given two files:
1. package com;
2. public class MyClass {
3. public static void howdy() {System.out.print("howdy "); }
4. public static final int myConstant = 343;
5. public static final MyClass mc = new MyClass();
6. public int instVar = 42;
7. }
11. import static com. MyClass.*;
12. public class TestImports {
13. public static void main(String[] args)
14. System.out.print(myConstant + " ");
15. howdy();
16. System.out.print(mc.instVar + " ");
17. System.out.print(instVar + " ");
18. } }
What is the result (Choose ALL that apply.)

A．343 howdy 42 42
B．Compilation fails due to an error on line 11.
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 17.
单项选择题

Given this code in a method:
4. int x = 0;
5. int[] primes = {1,2,3,5};
6. for(int i: primes)
7. switch (i) {
8. case 1: x += i;
9. case 5: x += i;
10. default: x += i;
11. case 2: x += i;
12. }
13. System.out.println (x);
What is the result

A．11
B．13
C．24
D．27
E．Compilation fails due to an error on line 7.
F．Compilation fails due to an error on line 10.
G．Compilation fails due to an error on line 11.
多项选择题

Given:
1. import java.util.*;
2. public class Elway {
3. public static void main(String[] args) {
4. ArrayList[] ls = new ArrayList[3];
5. for(int i = 0; i ＜ 3; i++) {
6. ls[i] = new ArrayList();
7. ls[i].add("a" + i);
8. }
9. Object o = ls;
10. do3(ls) ;
11. for(int i = 0; i ＜ 3; i++) {
12. // insert code here
13. }
14. }
15. static Object do3(ArrayList[] a) {
16. for(int i = 0; i ＜ 3; i++) a[i] .add("e");
17. return a;
18. } }
And the following fragments:
Ⅰ. System.out.print (o [i ] + " ");
Ⅱ. System.out.print((ArrayList[]) [i] + " ");
Ⅲ. System.out.print( ((Object[])o) [i] + " ");
Ⅳ. System.out.print(((ArrayList[])o) [i] + " ");
If the fragments are added to line 12, independently, which are true (Choose all that apply.)

A．Fragment Ⅰ will compile.
B．Fragment Ⅱ will compile.
C．Fragment Ⅲ will compile.
D．Fragment Ⅳ will compile.
E．Compilation fails due to other errors.
F．Of those that compile, the output will be [a0] [a1] [a2]
G．Of those that compile, the output will be [a0, e] [a1, e] [a2, e]
多项选择题

Given:
1. enum MyEnum {HI, ALOHA, HOWDY};
2. public class PassEnum {
3. public static void main(String[] args) {
4. PassEnum p = new PassEnum();
5. MyEnum[] v = MyEnum.values();
6. v = MyEnum.getValues();
7. for(MyEnum me: MyEnum.values()) p.getEnum(me);
8. for(int x = 0; x＜MyEnum.values().length; x++) p.getEnum(v[x]);
9. for(int x = 0; x ＜ MyEnum.length; x++) p.getEnum(v[x]);
10. for(MyEnum me: v) p.getEnum(me);
11. }
12. public void getEnum(MyEnum e) {
13. System.out.print(e + " ");
14. } }
Which line(s) of code will cause a compiler error (Choose all that apply.)

A．line 1
B．line 5
C．line 6
D．line 7
E．line 8
F．line 9
G．line 10
H．line 12
单项选择题

Given:
3. public class Drip extends Thread {
4. public static void main(String[] args) {
5. Thread t1 = new Thread(new Drip());
6. t1.start();
7. t1.join();
8. for(int i = 0; i ＜ 1000; i++) // Loop #1
9. System.out.print(Thread.currentThread() .getName() + " ");
10. }
11. public void run() {
12. for(int i = 0; i ＜ 1000; i++) // Loop #2
13. System.out.print(Thread.currentThread() .getName() + " ");
14. } }
Which are true (Choose all that apply.)

A．Compilation fails.
B．An exception is thrown at runtime.
C．Loop #1 will run most of its iterations before Loop #2.
D．Loop #2 will run most of its iterations before Loop #1.
E．There is no way to predict which loop will mostly run first.
单项选择题

Given this code in a method:
5. int x = 3;
6. for(int i = 0; i ＜ 3; i++) {
7. if(i == 1) x = x++;
8. if(i % 2 == 0 && x % 2 == 0) System.out.print(".");
9. if(i % 2 == 0 && x % 2 == 1) System.out.print("-");
10. if(i == 2 ^ x == 4) System.out.print(",");
11. }
12. System. out.println ("＜");
What is the result

A．-.,＜
B．--,＜
C．-.,,＜
D．--,,＜
E．-.-,,＜
F．Compilation fails.
多项选择题

Given:
2. public class Incomplete {
3. public static void main(String[] args) { // change code here
4. // insert code here
5. new Incomplete() .doStuff();
6. // insert code here
…
10. }
11. static void doStuff() throws Exception
12. throw new Exception();
13. }
Which are true (Choose all that apply.)

A．Compilation succeeds with no code changes.
B．Compilation succeeds if main() is changed to throw an Exception.
C．Compilation succeeds if a try-catch is added, surrounding line 5.
D．Compilation succeeds if a try-finally is added, surrounding line 5.
E．Compilation succeeds only if BOTH main() declares an Exception AND a try-catch is added, surrounding line 5.
单项选择题

Given the proper imports, and given:
24. Date d1 = new Date();
25. Date d2 = d1;
26. System.out.println(d1);
27. d2.setTime(d1.getTime() + (7 * 24 * 60 * 60));
28. System.out.println(d2);
Which are true (Choose all that apply.)

A．Compilation fails.
B．An exception is thrown at runtime.
C．Some of the output will be today"s date.
D．Some of the output will be next week"s date.
E．Some of the output will represent the Java "epoch" (i.e., January 1, 1970).
单项选择题

Given:
2. interface Machine { }
3. interface Engine { }
4. abstract interface Tractor extends Machine, Engine {
5. void pullStuff();
6. }
7. class Deere implements Tractor {
8. public void pullStuff() {System.out.print("pulling "); }
9. }
10. class LT255 implements Tractor extends Deere {
11. public void pullStuff() {System.out.print("pulling harder "); }
12. }
13. public class LTI55 extends Deere implements Tractor, Engine { }
What is the result (Choose all that apply.)

A．Compilation succeeds.
B．Compilation fails because of error(s) in Tractor.
C．Compilation fails because of error(s) in Deere.
D．Compilation fails because of error(s) in LT255.
E．Compilation fails because of error(s) in LT155.
单项选择题

Given this code in a method:
5. boolean[] ba = {true, false};
6. short[] [] gr = {{1,2}, {3,4}};
7. int i = 0;
8. for( ; i ＜ i0; ) i++;
9. for(short s: gr) ;
10. for(int j = 0, k = 10; k ＞ j; ++j, k--);
11. for(int j = 0; j ＜ 3; System.out.println(j++))
12. for(Boolean b: ba);
What is the result (Choose all that apply.)

A．Compilation succeeds.
B．Compilation fails due to an error on line 8.
C．Compilation fails due to an error on line 9.
D．Compilation fails due to an error on line 10.
E．Compilation fails due to an error on line 11.
F．Compilation fails due to an error on line 12.
多项选择题

Given:
2. class Pancake { }
3. class BlueberryPancake extends Pancake { }
4. public class SourdoughBlueberryPancake2 extends BlueberryPancake {
5. public static void main(String[] args) {
6. Pancake p4 = new SourdoughBlueberryPancake2();
7. // insert code here
8. } }
And the following six declarations (which are to be inserted independently at line 7):
Ⅰ. Pancake p5 = p4;
Ⅱ. Pancake p6 = (BlueberryPancake)p4;
Ⅲ. BlueberryPancake b2 = (BlueberryPancake)p4;
Ⅳ. BlueberryPancake b3 = (SourdoughBlueberryPancake2)p4;
Ⅴ. SourdoughBlueberryPancake2 s1 = (BlueberryPancake)p4;
Ⅵ. SourdoughBlueberryPancake2 s2 = (SourdoughBlueberryPancake2)p4;
Which are true (Choose all that apply.)

A．All six declarations will compile.
B．Exactly one declaration will not compile.
C．More than one of the declarations will not compile.
D．Of those declarations that compile, none will throw an exception.
E．Of those declarations that compile, exactly one will throw an exception.
F．Of those declarations that compile, more than one will throw an exception.
单项选择题

Given:
3. class IcelandicHorse {
4. void tolt() {System.out.print("4-beat "); }
5. }
6. public class Vafi extends IcelandicHorse {
7. public static void main(String[] args) {
8. new Vafi() .go();
9. new IcelandicHorse() .tolt();
10. }
11. void go() {
12. IcelandicHorse h1 = new Vafi();
13. hl.tolt()
14. Vafi v = (Vafi) h1;
15. v.tolt();
16. }
17. void tolt() {System.out.print("pacey "); }
18. }
What is the result (Choose all that apply.)

A．4-beat pacey pacey
B．pacey pacey 4-beat
C．4-beat 4-beat 4-beat
D．4-beat pacey 4-beat
E．pacey, followed by an exception
F．4-beat, followed by an exception
单项选择题

Given:
1. class MyException extends RuntimeException { }
2. public class Houdini {
3. public static void main(String[] args) throws Exception
4. throw new MyException();
5. System.out.println("success");
6. } }
Which are true (Choose all that apply.)

A．The code runs without output.
B．The output "success" is produced.
C．Compilation fails due to an error on line 1.
D．Compilation fails due to an error on line 3.
E．Compilation fails due to an error on line 4.
F．Compilation fails due to an error on line 5.
单项选择题

Given:
3. public class Avast {
4. static public void main (String[] scurvy)
5. System.out.print (scurvy[1] + " ");
6. main(scurvy[2]);
7. }
8. public static void main(String dogs) {
9. assert (dogs == null);
10. System.out.println(dogs);
11. } }
And, if the code compiles, the command-line invocation:
java Avast -ea 1 2 3
What is the result (Choose all that apply.)

A．1 2
B．2 3
C．Compilation fails due to an error on line 4.
D．Compilation fails due to an error on line 6.
E．Compilation fails due to an error on line 8.
F．Compilation fails due to an error on line 9.
G．Some output is produced and then an AssertionError is thrown.
多项选择题

Given:
2. class Wheel {
3. Wheel(int s) {size = s; }
4. int size;
5. void spin() {System.out.print(size + "inch wheel spinning, "); }
6. }
7. public class Bicycle {
8. public static void main(String[] args) {
9. Wheel[] wa = {new Wheel(15), new Wheel(17)};
10. for(Wheel w: wa)
11. w.spin();
12. } }
Which are true (Choose all that apply.)

A．Compilation fails.
B．If size was private, the degree of coupling would change.
C．If size was private, the degree of cohesion would change.
D．The Bicycle class is tightly coupled with the Wheel class.
E．The Bicycle class is loosely coupled with the Wheel class.
F．If size was private, the degree of encapsulation would change.
单项选择题

Given:
2. public class Mouthwash {
3. static int x = 1;
4. public static void main(String[] args)
5. int x = 2;
6. for(int i=0; i＜ 3; i++) {
7. if(i==1) System. out.print(x + " ");
8. }
9. go();
10. System.out.print(x + " " + i);
11. }
12. static void go() {int x = 3; }
13. }
What is the result

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

Given the proper imports, and given:
23. String s = "123 888888 x 345 -45";
24. Scanner sc = new Scanner(s);
25. while(sc.hasNext())
26. if(sc.hasNextShort())
27. System.out.print(sc.nextShort() + " ");
What is the result

A．The output is 123 345
B．The output is 123 345 -45
C．The output is 123 888888 345 -45
D．The output is 123 followed by an exception.
E．The output is 123 followed by an infinite loop.
多项选择题

Given:
1. interface Horse {public void nicker(); }
Which will compile (Choose all that apply.)

A．public class Eyra implements Horse {public void nicker() { } }
B．public class Eyra implements Horse {public void nicker(int x) { } }
C．public class Eyra implements Horse {public void nicker() {System.out.println("huhuhuhuh..."); }}
D．public abstract class Eyra implements Horse {public void nicker(int loud) { }}
E．public abstract class Eyra implements Horse {public void nicker(int loud);}
单项选择题

Given:
2. public class LaoTzu extends Philosopher
3. public static void main(String[] args)
4. new LaoTzu();
5. new LaoTzu("Tigger");
6. }
7. LaoTzu() {this("Pooh"); }
8. LaoTzu(String s) {super(s); }
9. }
10. class Philosopher {
11. Philosopher(String s) {System.out.print(s + " "); }
12. }
What is the result

A．Pooh Pooh
B．Pooh Tigger
C．Tigger Pooh
D．Tigger Tigger
E．Compilation fails due to a single error in the code.
F．Compilation fails due to multiple errors in the code.
多项选择题

Which are capabilities of Java"s assertion mechanism (Choose all that apply.)

A．You can, at the command line, enable assertions for a specific class.
B．You can, at the command line, disable assertions for a specific package.
C．You can, at runtime, enable assertions for any version of Java.
D．It"s considered appropriate to catch and handle an AssertionError programmatically.
E．You can programmatically test whether assertions have been enabled without throwing an AssertionError.
多项选择题

Given:
4. public class Stone implements Runnable {
5. static int id = i;
6. public void run() {
7. try {
8. id = 1 - id;
9. if(id == 0) {pick(); } else {release(); }
10. } catch (Exception e) { }
11. }
12. private static synchronized void pick() throws Exception {
13. System.out.print ("P "); System.out.print("Q ");
14. }
15. private synchronized void release() throws Exception {
16. System.out.print("R "); System.out.print("S ");
17. }
18. public static void main(String[] args) {
19. Stone st = new Stone();
20. new Thread(st) .start();
21. new Thread(st) .start();
22. } }
Which are true (Choose all that apply.)

A．The output could be P Q R S
B．The output could be P R S Q
C．The output could be P R Q S
D．The output could be P Q P Q
E．The program could cause a deadlock.
F．Compilation fails.
单项选择题

Given:
3. public class States {
4. static String s;
5. static Boolean b;
6. static Boolean t1() {return new Boolean("howdy");
7. static boolean t2() {return new Boolean(s); }
8. public static void main(String[] args) {
9. if(t1()) System.out.print("t1 ");
10. if(!t2()) System.out.print("t2 ");
11. if(t1() != t2()) System.out.print("!= ");
12. }
13. }
Which are true (Choose all that apply.)

A．Compilation fails.
B．No output is produced.
C．The output will contain "t1 "
D．The output will contain "t2 "
E．The output will contain "!= "
F．The output is "t1 ", followed by an exception.
多项选择题

Which are valid command-line switches when working with assertions (Choose all that apply.)

A．-ea
B．-da
C．-dsa
D．-eva
E．-enableassertions
多项选择题

Given:
4. class Account {Long acctNum, password; }
5. public class Banker {
6. public static void main(String[] args) {
7. new Banker() .go();
8. // do more stuff
9. }
10. void go() {
11. Account a1 = new Account();
12. al.acctNum = new Long("1024");
13. Account a2 = a1;
14. Account a3 = a2;
15. a3.password = a1.acctNum.longValue();
16. a2.password = 4455L;
17. } }
When line 8 is reached, which are true (Choose all that apply.)

A．a1.acctNum == a3.password
B．a1.password == a2.password
C．Three objects are eligible for garbage collection.
D．Four objects are eligible for garbage collection.
E．Six objects are eligible for garbage collection.
F．Less than three objects are eligible for garbage collection.
G．More than six objects are eligible for garbage collection.
单项选择题

Given:
2. public class Coyote {
3. public static void main(String[] args)
4. int x = 4;
5. int y = 4;
6. while((x = jump(x)) ＜ 8)
7. do {
8. System.out.print(x + " ");
9. } while ((y = jump(y)) ＜ 6);
10. }
11. static int jump(int x) {return ++x; }
12. }
What is the result

A．5 5 6 6
B．5 5 6 7
C．5 5 6 6 7
D．5 6 5 6 7
E．Compilation fails due to a single error.
F．Compilation fails due to multiple errors.
多项选择题

Given:
2. class Engine {
3. public class Piston {
4. static int count = 0;
5. void go() {System.out.print(" pump " + ++count); }
6. }
7. public Piston getPiston() {return new Piston(); }
8. }
9. public class Auto {
10. public static void main(String[] args) {
11. Engine e = new Engine();
12. // Engine.Piston p = e.getPiston();
13. e.Piston p = e.getPiston();
14. p.go(); p.go();
15. } }
In order for the code to compile and produce the output" pump 1 pump 2", which are true (Choose all that apply.)

A．The code is correct as it stands.
B．Line 4 must be changed, count can"t be declared "static"
C．Line 12 must be un-commented, and line 13 must be removed.
D．Somewhere in the code, a second instance of Piston must be instantiated.
E．There are errors in the code that must be fixed, outside of lines 4, 12, and 13.
单项选择题

Given:
2. public class Juggler extends Thread {
3. public static void main(String[] args) {
4. try {
5. Thread t = new Thread(new Juggler());
6. Thread t2 = new Thread(new Juggler());
7. } catch (Exception e) {System.out.print("e "); }
8. }
9. public void run() {
10. for(int i = 0; i ＜ 2; i++) {
11. try {Thread.sleep(500); }
12. catch(Exception e) {System.out.print("e2 "); }
13. System.out.print(Thread.currentThread() .getName() + " ");
14. } } }
Which are true (Choose all that apply.)

A．Compilation fails.
B．No output is produced.
C．The output could be Thread-1 Thread-1 e
D．The output could be Thread-1 Thread-1 Thread-3 Thread-3
E．The output could be Thread-1 Thread-3 Thread-1 Thread-3
F．The output could be Thread-1 Thread-1 Thread-3 Thread-2
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