1. class TestA {  2. TestB b;  3. TestA() {  4. b = new TestB(this);  5. }  6. }  7. class TestB {  8. TestA a;  9. TestB(TestA a) {  10. this.a = a;  11. }  12. }  13. class TestAll {  14. public static void main (String args[]) {  15. new TestAll().make

题目

1. class TestA {  2. TestB b;  3. TestA() {  4. b = new TestB(this);  5. }  6. }  7. class TestB {  8. TestA a;  9. TestB(TestA a) {  10. this.a = a;  11. }  12. }  13. class TestAll {  14. public static void main (String args[]) {  15. new TestAll().makeThings(); 16. // ...code continues on  17. }  18. void makeThings() {  19. TestA test = new TestA(); 20. }  21. }  Which two statements are true after line 15, before main completes?()

  • A、 Line 15 causes a stack overflow.
  • B、 An exception is thrown at runtime.
  • C、 The object referenced by a is eligible for garbage collection.
  • D、 The object referenced by b is eligible for garbage collection.
  • E、 The object referenced by a is not eligible for garbage collection.
  • F、 The object referenced by b is not eligible for garbage collection.
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相似问题和答案

第1题:

1. public class SimpleCalc {  2. public int value;  3. public void calculate() { value += 7; }  4. } And:  1. public class MultiCalc extends SimpleCalc {  2. public void calculate() { value -= 3; }  3. public void calculate(int multiplier) {  4. calculate();  5. super.calculate();  6. value *=multiplier;  7. }  8. public static void main(String[] args) {  9. MultiCalc calculator = new MultiCalc();  10. calculator.calculate(2);  11. System.out.println(”Value is: “+ calculator.value);  12. }  13. }  What is the result?() 

  • A、 Value is: 8
  • B、 Compilation fails.
  • C、 Value is: 12
  • D、 Value is: -12
  • E、 The code runs with no output.
  • F、 An exception is thrown at runtime.

正确答案:A

第2题:

1. public class GoTest {  2. public static void main(String[] args) {  3. Sente a = new Sente(); a.go();  4. Goban b = new Goban(); b.go();  5. Stone c = new Stone(); c.go();  6. }  7. } 8.  9. class Sente implements Go {  10. public void go() { System.out.println(”go in Sente.”); }  11. }  12.  13. class Goban extends Sente {  14. public void go() { System.out.println(”go in Goban”); }  15. }  16.  17. class Stone extends Goban implements Go { }  18.  19. interface Go { public void go(); }  What is the result?() 

  • A、 go in Goban     go in Sente go in Sente
  • B、 go in Sente      go in Sente go in Goban
  • C、 go in Sente     go in Goban go in Goban
  • D、 go in Goban    go in Goban go in Sente
  • E、 Compilation fails because of an error in line 17.

正确答案:C

第3题:

classTestA{publicvoidstart(){System.out.println(”TestA”);}}publicclassTestBextendsTestA{publicvoidstart(){System.out.println(”TestB”);}publicstaticvoidmain(String[]args){((TestA)newTestB()).start();}}Whatistheresult?()

A.TestA

B.TestB

C.Compilationfails.

D.Anexceptionisthrownatruntime.


参考答案:B

第4题:

class TestA {  public void start() { System.out.println(”TestA”); }  }  public class TestB extends TestA {  public void start() { System.out.println(”TestB”); } public static void main(String[] args) {  ((TestA)new TestB()).start();  }  }  What is the result?() 

  • A、 TestA
  • B、 TestB
  • C、 Compilation fails.
  • D、 An exception is thrown at runtime.

正确答案:B

第5题:

1. class A {  2. public byte getNumber ()  {  3.   return 1;  4.   }  5. }  6.    7. class B extends A {  8. public short getNumber()  {  9.  return 2;  10. }  11.    12. public static void main (String args[]) {   13.    B  b = new B ();  14.      System.out.printIn(b.getNumber())     15.   }  16. }    What is the result?()  

  • A、 Compilation succeeds and 1 is printed.
  • B、 Compilation succeeds and 2 is printed.
  • C、 An error at line 8 causes compilation to fail.
  • D、 An error at line 14 causes compilation to fail.
  • E、 Compilation succeeds but an exception is thrown at line 14.

正确答案:C

第6题:

1. public class Outer{  2. public void someOuterMethod() {  3. // Line 3  4. }  5. public class Inner{}  6. public static void main( String[]argv ) {  7. Outer o = new Outer();  8. // Line 8  9. }  10. }  Which instantiates an instance of Inner?()  

  • A、 new Inner(); // At line 3
  • B、 new Inner(); // At line 8
  • C、 new o.Inner(); // At line 8
  • D、 new Outer.Inner(); // At line 8

正确答案:A

第7题:

1. public class A {  2. void A() {  3. System.out.println(“Class A”);  4. }  5. public static void main(String[] args) {  6. new A();  7. }  8. }  What is the result?()  

  • A、 Class A
  • B、 Compilation fails.
  • C、 An exception is thrown at line 2.
  • D、 An exception is thrown at line 6.
  • E、 The code executes with no output.

正确答案:E

第8题:

1. class A {  2. public int getNumber(int a) {  3.     return a + 1;  4. }  5. }  6.    7. class B extends A {  8. public int getNumber (int a) {  9. return a + 2  10. }  11.    12. public static void main (String args[])  {  13. A a = new B();  14. System.out.printIn(a.getNumber(0));  15.    } 16. }     What is the result?()  

  • A、 Compilation succeeds and 1 is printed.
  • B、 Compilation succeeds and 2 is printed.
  • C、 An error at line 8 causes compilation to fail.
  • D、 An error at line 13 causes compilation to fail.
  • E、 An error at line 14 causes compilation to fail.

正确答案:B

第9题:

1. class Pizza {  2. java.util.ArrayList toppings;  3. public final void addTopping(String topping) {  4. toppings.add(topping); 5. }  6. }  7. public class PepperoniPizza extends Pizza {  8. public void addTopping(String topping) {  9. System.out.println(”Cannot add Toppings”);  10. }  11. public static void main(String[] args) {  12. Pizza pizza = new PepperoniPizza();  13. pizza.addTopping(”Mushrooms”);  14. }  15. }  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.

正确答案:A

第10题:

1. public class Test { 2. public static String output =””; 3.  4. public static void foo(int i) { 5. try { 6. if(i==1) { 7. throw new Exception(); 8. } 9. output += “1”; 10. } 11. catch(Exception e) { 12. output += “2”; 13. return; 14. } 15. finally { 16. output += “3”;17. } 18. output += “4”; 19. } 20.  21. public static void main(String args[]) { 22. foo(0); 23. foo(1); 24.  25. }26. } What is the value of the variable output at line 23?()


正确答案:13423

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