Set 24

Multiple Choice Question

QID: 
382

Note: This question may be considered too advanced for this exam.

Given the declaration :
interface Worker { void perform_work(); }

which of the following methods/classes are valid?

Select 2 options 

A.    Worker getWorker(int i){   
return new Worker(){  
 public void perform_work() {         
System.out.println(i); }    }; } 
B.    Worker getWorker(final int i){   
return new Worker() {  
 public void perform_work() {   
 System.out.println(i); }    }; } 
C.    Worker getWorker(int i){  
 int x = i;   
class MyWorker implements Worker  {          
 public void perform_work() {
System.out.println(x); }    }; 
 return new MyWorker(); } 
D.    Worker getWorker(final int i){   
class MyWorker implements Worker {       
  public void perform_work() { 
System.out.println(i); }    };  
 return new MyWorker(); }

Multiple Choice Question

QID: 
381

What, if anything, is wrong with the following code?

// Filename: TestClass.java 

class TestClass implements T1, T2{   
public void m1(){} } 
interface T1{  
 int VALUE = 1;   
void m1(); } 
interface T2{   
int VALUE = 2;  
 void m1(); }

Select 1 option

A. TestClass cannot implement them both because it leads to ambiguity. 
B. There is nothing wrong with the code. 
C. The code will work fine only if VALUE is removed from one of the interfaces. 
D. The code will work fine only if m1() is removed from one of the interfaces. 
E. None of the above. 

Multiple Choice Question

QID: 
380

Given the following code, which statements are true?

interface Automobile { String describe(); }
class FourWheeler implements Automobile{
String name;
public String describe(){ return " 4 Wheeler " + name; }
}
class TwoWheeler extends FourWheeler{
String name;
public String describe(){ return " 2 Wheeler " + name; }
}

Select 3 options

A. An instance of TwoWheeler is also an instance of FourWheeler.
B. An instance of TwoWheeler is a valid instance of Automobile.
C. The use of inheritance is not justified here because a TwoWheeler is not really a FourWheeler.
D. The code will compile only if name is removed from TwoWheeler.
E. The code will fail to compile.

Multiple Choice Question

QID: 
379

Consider the following interface definition:

interface Bozo{
int type = 0;
public void jump();
}
Now consider the following class:
public class Type1Bozo implements Bozo{
public Type1Bozo(){
type = 1;
}
public void jump(){
System.out.println("jumping..."+type);
}
public static void main(String[] args){
Bozo b = new Type1Bozo();
b.jump();
}
}

What will the program print when compiled and run?

Select 1 option

A. jumping...0
B. jumping...1
C. This program will not compile.
D. It will throw an exception at runtime.

Multiple Choice Question

QID: 
378

Which of these statements about interfaces are true?

Select 3 options

A. Interfaces are abstract by default.
B. An interface can have static methods.
C. All methods in an interface are abstract although you need not declare them to be so.
D. Fields of an interface may be declared as transient or volatile but not synchronized.
E. interfaces cannot be final.

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