单项选择题

 public class ArrayTest {  
public static void main (Stringargs) { 
 float f1, f2;  
f1 = new float [10]; 
f2 = f1;  
System.out.printIn (“f2[0]=” + f2[0]);  
} 
}  
What is the result?()

A. It prints f2[0] = 0.0
B. It prints f2[0] = NaN
C. An error at line 5 causes compile to fail.
D. An error at line 6 causes compile to fail.
E. An error at line 6 causes an exception at runtime.


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3.单项选择题

public class Mycircle {  
public double radius;  
public double diameter;  
public void setRadius(double radius)  
this.radius = radius;  
this.diameter= radius * 2;  
}  
public double getRadius() { 
return radius;  
}  
Which statement is true?()  

A. The Mycircle class is fully encapsulated.
B. The diameter of a given MyCircle is guaranteed to be twice its radius.
C. Lines 6 and 7 should be in a synchronized block to ensure encapsulation.
D. The radius of a MyCircle object can be set without affecting its diameter.

4.多项选择题Which two statements are true?()

A. An inner class may be declared as static.
B. An anonymous inner class can be declared as public.
C. An anonymous inner class can be declared as private.
D. An anonymous inner class can extend an abstract class.
E. An anonymous inner class can be declared as protected.

6.单项选择题

class A {  
public byte getNumber () {  
return 1;  
}  
}  
class B extends A {  
public short getNumber() {  
return 2;  
}  
 public static void main (String args) {  
B b = new B ();  
 System.out.printIn(b.getNumber()) 
}  
}  
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.

7.单项选择题Which statement about static inner classes is true?()

A. An anonymous class can be declared as static.
B. A static inner class cannot be a static member of the outer class.
C. A static inner class does not require an instance of the enclosing class.
D. Instance members of a static inner class can be referenced using the class name of the static inner class.

8.多项选择题

class BaseClass{  
private float x= 1.0f;  
protected void setVar (float f) {x = f;}  
}  
class SubClass exyends BaseClass {  
private float x = 2.0f;  
//insert code here  8. }  
Which two are valid examples of method overriding?()

A. Void setVar(float f) {x = f;}
B. Public void setVar(int f) {x = f;}
C. Public void setVar(float f) {x = f;}
D. Public double setVar(float f) {x = f;}
E. Public final void setVar(float f) {x = f;}
F. Protected float setVar() {x=3.0f; return 3.0f; }

9.单项选择题

class A {  
public int getNumber(int a) {  
return a + 1;  
}  
}  
 class B extends A {  
public int getNumber (int a) {  
return a + 2  
}  
 public static void main (String args) {  
A a = new B();  
System.out.printIn(a.getNumber(0));  
}  
}  
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.

10.单项选择题

import java.awt.*;  
public class Test extends Frame {  
public Test() {  
add(new Label(“Hello”) );  
add(new TextField(“Hello”) );  
add(new Button(“Hello”) );  
pack();  
show();  
 }  
public static void main(String args) {  
new Test ();  
}  
}  
What is the result? () 

A. The code will not compile.
B. A Window will appear containing only a Button.
C. An IllegalArgumentException is thrown at line 6.
D. A Window button will appear but will not contain the Label, TextField, or Button.
E. A Window will appear containing a Label at the top, a TextField below the Label, and a Button  below the TextField.
F. A Window will appear containing a Label on the left, a TextField to the right of the Label, and a button to the right of the TextField.