Java语言程序设计单元测试3

临沂师范学院2009—2010学年度第1学期

《Java语言程序设计》单元测试3

I Single-choice Topic （30 points）

1. Assume double m =45.5, Which of the following statement output this variable value? ________

A. System.out.printf(“m =%f”,m);

B. System.out.printf(“m =%d”,m);

C. System.out.printf(“m =%s”,”m”);

D. System.out.printf(“m =%s”,m);

2. Which of the following initializer lists would correctly set the elements of array n?

A. int[] n = { 1, 2, 3, 4, 5 ,6,7,8 };.

B. array n[ int ] = { 1, 2, 3, 4, 5 ,6,7,8 };.

C. int n[ 5 ] = { 1; 2; 3; 4; 5 ;6;7;8 };.

D. int n = new int( 1, 2, 3, 4, 5 ,6,7,8);.

3. Which of the following elements should usually be private?________ A．methods B．constructors C．variables (or fields). D．All of the above

4. Analyze the following code and select the correct choice __________

public class Test {

public static void main(String[] args) { add(23, 67); }

public static void add(int n, int f) {System.out.println("return void”);}

public static int add(int x, int y) { System.out.println("return int");

return x; }}

A. The program displays return void.

B. The program displays long, long.

C. The program display an exception.

D. The program does not compile because the compiler cannot distinguish which info method to call.

5 What is k after the following block executed? __________

{ int i = 2; System.out.println("A message" + i );}

A. 1

B. 2

C. 3

D. k is not defined outside the block.

6. The visibility of these modifiers increases in this order:__________.

A. private, protected, none (if no modifier is used), and public.

B. private, none (if no modifier is used), protected, and public.

C. none (if no modifier is used), private, protected, and public.

D. none (if no modifier is used), protected, private, and public.

7.What is the output of running A? ___________

public class A extends B {

int x = 1;

public static void main(String[] args) {

System.out.print(new A().x);

System.out.print(new B().x); }}

class B { int x = 5; }

A. 1 5

B. 5 1

C. 1 1

D. 5 5

8. What modifier should you use on a class so that a class in the same package can access it but a class in a different package cannot access it______?

A. public

B. private

C. protected

D. Use the default modifier.

9. Which of the following classes cannot be extended_________?

class My { } B. abstract class My{ private test();}

C. class My {protected A() { };}

D. final class My {}

10. What is the output of the following code: _________

public class Test {

public static void main(String[] args) {

Object o1 = new Object(); Object o2 = new Object();

System.out.print((o1 == o2) + " " + (o1.equals(o2))); }}

A. false false

B. true true

C. false true

D. true false

11.Which of the following classes is an abstract class________?

abstract class A{ } B. public classA{ } C. final class A { } D. static class A { } 12. Which of the following declares an abstract method in an abstract Java class________?

A. public abstract method();

B. public abstract void method();

public void static Method(); D. public void method() {}

13.which of the following keywords is used to define an interface?_____