OCJP Preparation - Java Inner Classes

1. Given the program

What is the output?

• A. 2
• B. 3
• C. 1 2
• D. 2 3
• E. 1 2 3
• F. Compilation fails.
• G. An exception is thrown at runtime.

Answer: D

Given the command line java Test:

2. What become the output?

• A. Compilation fails.
• B. An exception is thrown at runtime.
• C. doStuff x = 6 main x = 6
• D. doStuff x = 6 main x = 7
• E. doStuff x = 7 main x = 6
• F. doStuff x = 7 main x = 7

Answer: B

3. Given the program

What become the output?

• A. Compilation fails.
• B. An exception is thrown at runtime.
• C. doStuff x = 6 main x = 6
• D. doStuff x = 5 main x = 5
• E. doStuff x = 5 main x = 6
• F. doStuff x = 6 main x = 5

Answer: D

4. Given the program

What become the output?

• A. 1
• B. 2
• C. Compilation fails.
• D. The code runs with no output.
• E. An exception is thrown at runtime.

Answer: C
The operator || is undefined for the argument type(s) int, boolean

5. Given the program

What become the output?

• A. null
• B. life
• C. universe
• D. everything
• E. Compilation fails.
• F. An exception is thrown at runtime.

Answer:
-> D is correct. This is a ternary nested in a ternary with a little unboxing thrown in. Both of the ternary expressions are false.
-> A, B, C, E, and F are incorrect based on the above.

6. Given the program

Which, inserted independently at line 5, will compile? (Choose all that apply.)

• A. b = (Number instanceof s);
• B. b = (s instanceof Short);
• C. b = s.instanceof(Short);
• D. b = (s instanceof Number);
• E. b = s.instanceof(Object);
• F. b = (s instanceof String);

Answer:
-> B and D correctly use boxing and instanceof together.
-> A is incorrect because the operands are reversed. C and E use incorrect instance of syntax. F is wrong because Short isn't in the same inheritance tree as String.