一、 选择

1、下面哪些是java语言中的关键字?

A sizeof

B abstract

C NULL

D Native

2、下面语句哪个是正确的?

A char='abc';

B long l=oxfff;

C float f=0.23;

D double=0.7E-3;

3、以下程序测试String 类的各种构造方法,试选出其运行效果。
  class STR{
   public static void main(String args[]){
    String s1=new String();
    String s2=new String("String 2");
    char chars[]={'a',' ','s','t','r','i','n','g'};
    String s3=new String(chars);
    String s4=new String(chars,2,6);
    byte bytes[]={0,1,2,3,4,5,6,7,8,9};
    StringBuffer sb=new StringBuffer(s3);
    String s5=new String(sb);
    System.out.println("The String No.1 is "+s1);
    System.out.println("The String No.2 is "+s2);
    System.out.println("The String No.3 is "+s3);
    System.out.println("The String No.4 is "+s4);
    System.out.println("The String No.5 is "+s5);
   }
  }

A The String No.1 is
   The String No.2 is String 2
   The String No.3 is a string
   The String No.4 is string
   The String No.5 is a string

B The String No.1 is
   The String No.2 is String 2
   The String No.3 is a string
   The String No.4 is tring
   The String No.5 is a string

C The String No.1 is
   The String No.2 is String 2
   The String No.3 is a string
   The String No.4 is strin
   The String No.5 is a string

D 以上都不对

4、下面语句段的输出结果是什么?
  int i = 9;
  switch (i) {
  default:
  System.out.println("default");
  case 0:
  System.out.println("zero");
  break;
  case 1:
  System.out.println("one");
  case 2:
  System.out.println("two"); }

A default

B default, zero

C error default clause not defined

D no output displayed

 

二、多项选择


1、下面哪些语句能够正确地生成5个空字符串?

A String a[]=new String[5]; for(int i=0;i<5;a[++]="");

B String a[]={"","","","",""};

C String a[5];

D String[5]a;

E String []a=new String[5]; for( int i=0;i<5;a[i++]=null);

2、下面哪些选项将是下述程序的输出?
  public class Outer{
  public static void main(String args[]){
  Outer: for(int i=0; i<3; i++)
   inner:for(int j=0;j<3;j++){
    if(j>1) break;
    System.out.println(j+"and"+i);
   }
  }
  }

A 0 and 0

B 0 and 1

C 0 and 2

D 0 and 3

E 2 and 2

F 2 and 1

G 2 and 0

3、下面哪个语句正确地声明一个整型的二维数组?

A int a[][] = new int[][];

B int a[10][10] = new int[][];

C int a[][] = new int[10][10];

D int [][]a = new int[10][10];

E int []a[] = new int[10][10];



三、 编程题

1、编写一个程序,用选择法对数组a[]={20,10,50,40,30,70,60,80,90,100}进行从大到小的排序。