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SCJP 5.0 - Generics Mock Exam - 3

1)what is the result compiling and running the following piece of code?

import java.util.*; 
class Test { 
	public static void main(String [] args) { 
		Set vals = new TreeSet<String>(); 
		vals.add("one"); 
		vals.add(1); 
		vals.add("two"); 
		System.out.println(vals); 
	} 
} 

a)Does not Compile
b)Compiles with warning and prints output [one, 1, two]
c)Compiles without warning and prints output [one, 1, two]
d)Compiles with warning and throws exception at runtime
e)Compiles without warning and throws exception at runtime

Answer:

1) D
Compiles with warning due to un-safe assignment List vals = new ArrayList<String>();
Since TreeSet<String> is used, it will try to sort by natural order. Due to the presence of Integer (vals.add(1);) in the collection, it will throw ClassCastException at runtime(While try to cast Integer in to String).

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