1. public class X implements Runnable( 2. private int x; 3. private int y; 4. 5. public static void main(String[]args) 6. X that = new X(); 7. (new Thread(that)).start(); 8. (new Thread(that)).start(); 9. ) 10. 11. public void run() ( 12. for (;;) ( 13. x++; 14. y++; 15. System.out.printIn(“x=” + x + “, y = ” + y); 16. ) 17. ) What is the result?()A、 Errors at lines 7 and 8 cause compilation to fail.B、 The program prints pairs of values for x and y that might not always be the same on the same line (for example, “x=2, y=1”).C、 The program prints pairs of values for x and y that are always the same on the same line (for example, “x=1, y=1”. In addition, each value appears twice (for example, “x=1, y=1” followed by “x=1, y=1”).D、 The program prints pairs of values for x and y that are always the same on the same line (for example, “x=1, y=1”. In addition, each value appears only for once (for example, “x=1, y=1” followed by “x=2, y=2”).
1. public class X implements Runnable( 2. private int x; 3. private int y; 4. 5. public static void main(String[]args) 6. X that = new X(); 7. (new Thread(that)).start(); 8. (new Thread(that)).start(); 9. ) 10. 11. public void run() ( 12. for (;;) ( 13. x++; 14. y++; 15. System.out.printIn(“x=” + x + “, y = ” + y); 16. ) 17. ) What is the result?()
- A、 Errors at lines 7 and 8 cause compilation to fail.
- B、 The program prints pairs of values for x and y that might not always be the same on the same line (for example, “x=2, y=1”).
- C、 The program prints pairs of values for x and y that are always the same on the same line (for example, “x=1, y=1”. In addition, each value appears twice (for example, “x=1, y=1” followed by “x=1, y=1”).
- D、 The program prints pairs of values for x and y that are always the same on the same line (for example, “x=1, y=1”. In addition, each value appears only for once (for example, “x=1, y=1” followed by “x=2, y=2”).
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下列程序片段中,能通过编译的是A.public abstract class Animal{ public void speak();}B.public abstract class Animal{ public void speak(){}}C.public class Animal{ public abstract void speak();}D.public abstract class Animal{ public abstract void speak(){}}
下列虚基类的声明中正确的是( )。A.class virtual B:public AB.virtual class B:public AC.class B:public A virtualD.class B:virtual public A
Given:Which two, inserted at line 11, will allow the code to compile?() A.public class MinMax? {B.public class MinMax? extends Number {C.public class MinMaxN extends Object {D.public class MinMaxN extends Number {E.public class MinMax? extends Object {F.public class MinMaxN extends Integer {
public class SomeException { } Class a: public class a { public void doSomething() { } } Class b: public class b extends a { public void doSomething() throws SomeException { } } Which is true about the two classes?() A、 Compilation of both classes will fail.B、 Compilation of both classes will succeed.C、 Compilation of class a will fail. Compilation of class b will succeed.D、 Compilation of class a will fail. Compilation of class a will succeed.
1. public class Target { 2. private int i = 0; 3. public int addOne() { 4. return ++i; 5. } 6. } And: 1. public class Client { 2. public static void main(String[] args) { 3. System.out.println(new Target().addOne()); 4. } 5. } Which change can you make to Target without affecting Client?() A、 Line 4 of class Target can be changed to return i++;B、 Line 2 of class Target can be changed to private int i = 1;C、 Line 3 of class Target can be changed to private int addOne() {D、 Line 2 of class Target can be changed to private Integer i = 0;
1. public interface A { 2. public void doSomething(String thing); 3. } 1. public class AImpl implements A { 2. public void doSomething(String msg) { } 3. } 1. public class B { 2. public A doit() { 3. // more code here 4. } 5. 6. public String execute() { 7. // more code here 8. } 9. } 1. public class C extends B { 2. public AImpl doit() { 3. // more code here 4. } 5. 6. public Object execute() { 7. // more code here 8. } 9. } Which statement is true about the classes and interfaces in the exhibit?() A、 Compilation will succeed for all classes and interfaces.B、 Compilation of class C will fail because of an error in line 2.C、 Compilation of class C will fail because of an error in line 6.D、 Compilation of class AImpl will fail because of an error in line 2.
1. public class a { 2. public void method1() { 3. try { 4. B b=new b(); 5. b.method2(); 6. // more code here 7. } catch (TestException te) { 8. throw new RuntimeException(te); 9. } 10. } 11. } 1. public class b { 2. public void method2() throws TestException { 3. // more code here 4. } 5. } 1. public class TestException extends Exception { 2. } Given: 31. public void method() { 32. A a=new a(); 33. a.method1(); 34. } Which is true if a TestException is thrown on line 3 of class b?()A、 Line 33 must be called within a try block.B、 The exception thrown by method1 in class a is not required to be caught.C、 The method declared on line 31 must be declared to throw a RuntimeException.D、 On line 5 of class a, the call to method2 of class b does not need to be placed in a try/catch block.
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 AB、 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.
Which three demonstrate an “is a” relationship?() A、 public class X { } public class Y extends X { }B、 public interface Shape { } public interface Rectangle extends Shape{ }C、 public interface Color { } public class Shape { private Color color; }D、 public interface Species { } public class Animal { private Species species; }E、 public class Person { } public class Employee { public Employee(Person person) { }F、 interface Component { } class Container implements Component { private Component[] children; }
interface Data { public void load(); } abstract class Info { public abstract void load(); } Which class correctly uses the Data interface and Info class?() A、 public class Employee extends Info implements Data { public void load() { /*do something*/ } }B、 public class Employee implements Info extends Data { public void load() { /*do something*/ } }C、 public class Employee extends Info implements Data { public void load() { /*do something */ } public void Info.load() { /*do something*/ } }D、 public class Employee implements Info extends Data { public void Data.load() { /*dsomething */ } public void load() { /*do something */ } }E、 public class Employee implements Info extends Data { public void load() { /*do something */ } public void Info.load(){ /*do something*/ } }F、 public class Employee extends Info implements Data{ public void Data.load() { /*do something*/ } public void Info.load() { /*do something*/ } }
Which two allow the class Thing to be instantiated using new Thing()?A、 public class Thing { }B、 public class Thing { public Thing() {} }C、 public class Thing { public Thing(void) {} }D、 public class Thing { public Thing(String s) {} }E、 public class Thing { public void Thing() {} public Thing(String s) {} }
Which the two demonstrate an “is a” relationship?()A、 public interface Person {} Public class Employee extends Person {}B、 public interface Shape {} public interface Rectangle extends Shape {}C、 public interface Color {} public class Shape { private Color color; }D、 public class Species {} public class Animal { private Species species; }E、 interface Component {} Class Container implements Component {private Component [] children;
Which two demonstrate an “is a” relationship?() A、 public interface Person { } public class Employee extends Person { }B、 public interface Shape { } public class Employee extends Shape { }C、 public interface Color { } public class Employee extends Color { }D、 public class Species { } public class Animal (private Species species;)E、 interface Component { } Class Container implements Component ( Private Component[ ]children; )
What produces a compiler error?() A、 class A { public A(int x) {} }B、 class A {} class B extends A { B() {} }C、 class A { A() {} } class B { public B() {} }D、 class Z { public Z(int) {} } class A extends Z {}
1. public class OuterClass { 2. private double d1 = 1.0; 3. // insert code here 4. } Which two are valid if inserted at line 3?() A、 static class InnerOne { public double methoda() { return d1; } }B、 static class InnerOne { static double methoda() { return d1; } }C、 private class InnerOne { public double methoda() { return d1; } }D、 protected class InnerOne { static double methoda() { return d1; } }E、 public abstract class InnerOne { public abstract double methoda(); }
1. class super { 2. public float getNum() {return 3.0f;} 3. } 4. 5. public class Sub extends Super { 6. 7. } Which method, placed at line 6, will cause a compiler error?() A、 Public float getNum() {return 4.0f; }B、 Public void getNum () { }C、 Public void getNum (double d) { }D、 Public double getNum (float d) {retrun 4.0f; }
1. public class enclosingone ( 2. public class insideone{} 3. ) 4. public class inertest( 5. public static void main (string[]args)( 6. enclosingone eo= new enclosingone (); 7. //insert code here 8. ) 9. ) Which statement at line 7 constructs an instance of the inner class?() A、 InsideOnew ei= eo.new InsideOn();B、 Eo.InsideOne ei = eo.new InsideOne();C、 InsideOne ei = EnclosingOne.new InsideOne();D、 EnclosingOne.InsideOne ei = eo.new InsideOne();
单选题interface Data { public void load(); } abstract class Info { public abstract void load(); } Which class correctly uses the Data interface and Info class?()A public class Employee extends Info implements Data { public void load() { /*do something*/ } }B public class Employee implements Info extends Data { public void load() { /*do something*/ } }C public class Employee extends Info implements Data { public void load() { /*do something */ } public void Info.load() { /*do something*/ } }D public class Employee implements Info extends Data { public void Data.load() { /*dsomething */ } public void load() { /*do something */ } }E public class Employee implements Info extends Data { public void load() { /*do something */ } public void Info.load(){ /*do something*/ } }F public class Employee extends Info implements Data{ public void Data.load() { /*do something*/ } public void Info.load() { /*do something*/ } }
多选题Which three demonstrate an “is a” relationship?()Apublic class X { } public class Y extends X { }Bpublic interface Shape { } public interface Rectangle extends Shape{ }Cpublic interface Color { } public class Shape { private Color color; }Dpublic interface Species { } public class Animal { private Species species; }Epublic class Person { } public class Employee { public Employee(Person person) { }Finterface Component { } class Container implements Component { private Component[] children; }
单选题1. public class enclosingone ( 2. public class insideone{} 3. ) 4. public class inertest( 5. public static void main (string[]args)( 6. enclosingone eo= new enclosingone (); 7. //insert code here 8. ) 9. ) Which statement at line 7 constructs an instance of the inner class?()A InsideOnew ei= eo.new InsideOn();B Eo.InsideOne ei = eo.new InsideOne();C InsideOne ei = EnclosingOne.new InsideOne();D EnclosingOne.InsideOne ei = eo.new InsideOne();
单选题public class SomeException { } Class a: public class a { public void doSomething() { } } Class b: public class b extends a { public void doSomething() throws SomeException { } } Which is true about the two classes?()A Compilation of both classes will fail.B Compilation of both classes will succeed.C Compilation of class a will fail. Compilation of class b will succeed.D Compilation of class a will fail. Compilation of class a will succeed.
多选题Which two allow the class Thing to be instantiated using new Thing()?Apublic class Thing { }Bpublic class Thing { public Thing() {} }Cpublic class Thing { public Thing(void) {} }Dpublic class Thing { public Thing(String s) {} }Epublic class Thing { public void Thing() {} public Thing(String s) {} }
单选题1. class super { 2. public float getNum() {return 3.0f;} 3. } 4. 5. public class Sub extends Super { 6. 7. } Which method, placed at line 6, will cause a compiler error?()A Public float getNum() {return 4.0f; }B Public void getNum () { }C Public void getNum (double d) { }D Public double getNum (float d) {retrun 4.0f; }
单选题现有: 1. interface Animal { 2. void eat(); 3. } 4. 5. // insert code here 6. 7. public class HouseCat extends Feline { 8. public void eat() { } 9. } 和五个声明: abstract class Feline implements Animal { } abstract class Feline implements Animal { void eat(); } abstract class Feline implements Animal { public void eat(); } abstract class Feline implements Animal { public void eat() { } } abstract class Feline implements Animal { abstract public void eat(); } 分别插入到第5行,有几个可以通过编译?()A0B1C2D3
单选题1. public class a { 2. public void method1() { 3. try { 4. B b=new b(); 5. b.method2(); 6. // more code here 7. } catch (TestException te) { 8. throw new RuntimeException(te); 9. } 10. } 11. } 1. public class b { 2. public void method2() throws TestException { 3. // more code here 4. } 5. } 1. public class TestException extends Exception { 2. } Given: 31. public void method() { 32. A a=new a(); 33. a.method1(); 34. } Which is true if a TestException is thrown on line 3 of class b?()A Line 33 must be called within a try block.B The exception thrown by method1 in class a is not required to be caught.C The method declared on line 31 must be declared to throw a RuntimeException.D On line 5 of class a, the call to method2 of class b does not need to be placed in a try/catch block.
多选题1. public class OuterClass { 2. private double d1 = 1.0; 3. // insert code here 4. } Which two are valid if inserted at line 3?()Astatic class InnerOne { public double methoda() { return d1; } }Bstatic class InnerOne { static double methoda() { return d1; } }Cprivate class InnerOne { public double methoda() { return d1; } }Dprotected class InnerOne { static double methoda() { return d1; } }Epublic abstract class InnerOne { public abstract double methoda(); }
多选题1. public class A { 2. public void method1() { 3. B b=new B(); 4. b.method2(); 5. // more code here 6. } 7. } 1. public class B { 2. public void method2() { 3.C c=new C(); 4. c.method3(); 5. // more code here 6. } 7. } 1. public class C { 2. public void method3() { 3. // more code here 4. } 5. } Given: 25. try { 26. A a=new A(); 27. a.method1(); 28. } catch (Exception e) { 29. System.out.print(”an error occurred”); 30. } Which two are true if a NullPointerException is thrown on line 3 of class C?()AThe application will crash.BThe code on line 29 will be executed.CThe code on line 5 of class A will execute.DThe code on line 5 of class B will execute.EThe exception will be propagated back to line 27.
单选题What produces a compiler error?()A class A { public A(int x) {} }B class A {} class B extends A { B() {} }C class A { A() {} } class B { public B() {} }D class Z { public Z(int) {} } class A extends Z {}