单项选择题
现有:
1.class Over {
2.int dolt (long x) { return 3; }
3. }
4.
5. class Under extends Over {
6.//insert code here
7. }
和四个方法:
short dolt (int y) { return 4; }
int dolt(long Xr long y) { return 4; }
private int dolt(short y) { return 4; }
protected int dolt (long x) { return 4; }
分别插入到第6行,有几个可以通过编译?()
A. 1
B. 2
C. 3
D. 4
点击查看答案&解析
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单项选择题
现有: class Guy {String greet() {return "hi"; } } class Cowboy extends Guy ( String greet() ( return "howdy ¨; ) ) class Surfer extends Guy (String greet() (return "dude! ";)) class Greetings { public static void main (String [] args) { Guy [] guys = ( new Guy(), new Cowboy(), new Surfer() ); for (Guy g: guys) System.out.print (g.greet()}; } } 结果为:()
A. hi howdy dude!
B.运行时异常被抛出。
C.第7行出现一个错误,编译失败。
D.第8行出现一个错误,编译失败。 -
单项选择题
现有: class Cat { Cat (int c) {System.out.print {"cat"+c+" "); } } class SubCat extends Cat { SubCat (int c){super (5); System.out.print ("cable");} SubCat() { this (4); } public static void main (String [] args) { SubCat s= new SubCat(); } } 结果为:()
A. cat5
B. cable
C. cat5 cable
D. cable cat5 -
单项选择题
现有: class Dog{ } class Harrier extends Dog { } class DogTest{ public static void main (String [] args) { Dog dl=new Dog(); Harrier hl=new Harrier(); Dog d2=hl; Harrier h2= (Harrier) d2; Harrier h3=d2; } } 下面哪一项是正确的?()
A.2个Dog对象被创建
B.2个Harrier对象被创建
C.3个Harrier对象被创建
D.编译失败
