Java OCA OCP Practice Question 839

Question

Consider the following code: 

interface Pet{ String getName ();  } 

class Bird implements Pet{ 
    public String name; 
    public Bird (String name){ 
        this.name = name; 
     } /*from  w w  w . j  ava 2 s .  co m*/
    public String getName (){ return name;  } 
} 

class Eagle extends Bird  {  
    public Eagle (String name){ 
        super (name); 
     } 
} 

public class Main  { 
    public static void main (String [] args) throws Exception  { 
        Pet f = new Eagle ("American Bald Eagle"); 
        //PRINT NAME HERE 
    } 
}

Which of the following lines of code will print the name of the Eagle object?

Select 3 options 

A. System .out.println (f.name); 
B. System .out.println (f.getName ()); 
C. System .out.println (((Eagle)f).name); 
D. System .out.println (((Bird)f).getName ()); 
E. System .out.println (Eagle.name); 
F. System .out.println (Eagle.getName (f)); 



Correct Options are  : B C D

Note

While accessing a method or variable, the compiler will only allow you to access a method or variable that is visible through the class of the reference.

When you try to use f.name, the class of the reference f is Pet and Pet has no field named "name", thus, it will not compile.

But when you cast f to Bird (or Eagle), the compiler sees that the class Bird (or Eagle, because Eagle inherits from Bird) does have a field named "name" so ((Eagle)f).name or ((Bird)f).name will work fine.

f.getName() will work because Pet does have a getName() method.




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