Cameron's SCJA Mock Exam Question (pg.200, 9-4)

[Rob Poulos]

Here is the question:

Given the following code snippet, What would be valid lines of code to replace the comment "//line xxx"?

Vector V = new Vector();
v.add(10.1F);
//line xxx

potential aswers (choose 1):

a) Double d = (Double)v.elementAt(0);
b) Float f = (Float)v.elementAt(0);
c) float f = (Float)v.elementAt(0);
d) int j = (Integer)v.elementAt(0);

According to the book, the correct answer is A and it explains that the other answers will compile but will trigger a runtime exception.

now. I tried this in Eclipse and found the following:

Vector v = new Vector();
v.add(10.1F);
Double d = (Double)v.elementAt(0);
System.out.println(d);

this results in a "Exception in thread "main" java.lang.ClassCastException: java.lang.Float cannot be cast to java.lang.Double" error

Vector v = new Vector();
v.add(10.1F);
Float f = (Float)v.elementAt(0);
System.out.println(f);

this results in the code successfully compiling and running; printing 10.1 to the system.out

Vector v = new Vector();
v.add(10.1F);
float f = (Float)v.elementAt(0);
System.out.println(f);

this results in the code successfully compiling and running; printing 10.1 to the system.out

Vector v = new Vector();
v.add(10.1F);
int j = (Integer)v.elementAt(0);
System.out.println(j);

this results in a "Exception in thread "main" java.lang.ClassCastException: java.lang.Float cannot be cast to java.lang.Integer" error

This being said, i would think both B and C would be the only valid answers. Or am i missing something?