Java OCA OCP Practice Question 2236

Question

Assuming the following program is executed with assertions enabled, which is the first line to throw an exception at runtime? 

1:  package mypkg; 
2:  public class Main { 
3:     public int m(int choices) { 
4:        assert choices++==10 : 1; 
5:        assert true!=false : new StringBuilder("Answer2"); 
6:        assert(null==null) : new Object(); 
7:        assert ++choices==11 : "Answer4"; 
8:        assert 2==3 : ""; 
9:        return choices; 
10:    } //from   w  w  w . j a v  a  2  s.co  m
11:    public final static void main(String... students) { 
12:       try { 
13:          new Main().m(10); 
14:       } catch (Error e) { 
15:          System.out.print("Bad idea"); 
16:          throw e; 
17:       } 
18:    } 
19: }
  • A. Line 4
  • B. Line 5
  • C. Line 6
  • D. Line 7
  • E. Line 8
  • F. None of the above since the class does not compile


D.

Note

The Main class, including all five assert statements, compiles without issue, making Option F incorrect.

The first three assert statements on lines 4, 5, and 6 evaluate to true, not triggering any exceptions, with choices updated to 11 after the first assertion is executed.

Lines 4 and 7 demonstrate the very bad practice of modifying data in an assertion statement, which can trigger side effects.

Regardless of whether an assertion error is thrown, turning on/off assertions potentially changes the value returned by m().

At line 7, the assertion statement 12==11 evaluates to false, triggering an AssertionError and making Option D the correct answer.

The main() method catches and rethrows the AssertionError.

Like writing assertion statements that include side effects, catching Error is also considered a bad practice.

Note that line 8 also would trigger an AssertionError, but it is never reached due to the exception on line 7.




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