Java Programming - Language Fundamentals

Exercise :: Language Fundamentals - General Questions

11. 

Which one is a valid declaration of a boolean?

A. boolean b1 = 0;
B. boolean b2 = 'false';
C. boolean b3 = false;
D. boolean b4 = Boolean.false();
E. boolean b5 = no;

Answer: Option C

Explanation:

A boolean can only be assigned the literal true or false.

12. 

Which three are valid declarations of a float?

  1. float f1 = -343;
  2. float f2 = 3.14;
  3. float f3 = 0x12345;
  4. float f4 = 42e7;
  5. float f5 = 2001.0D;
  6. float f6 = 2.81F;

A. 1, 2, 4
B. 2, 3, 5
C. 1, 3, 6
D. 2, 4, 6

Answer: Option C

Explanation:

(1) and (3) are integer literals (32 bits), and integers can be legally assigned to floats (also 32 bits). (6) is correct because (F) is appended to the literal, declaring it as a float rather than a double (the default for floating point literals).

(2), (4),and (5) are all doubles.


13. 

Which is a valid declarations of a String?

A. String s1 = null;
B. String s2 = 'null';
C. String s3 = (String) 'abc';
D. String s4 = (String) '\ufeed';

Answer: Option A

Explanation:

Option A sets the String reference to null.

Option B is wrong because null cannot be in single quotes.

Option C is wrong because there are multiple characters between the single quotes ('abc').

Option D is wrong because you can't cast a char (primitive) to a String (object).


14. 

What is the numerical range of a char?

A. -128 to 127
B. -(215) to (215) - 1
C. 0 to 32767
D. 0 to 65535

Answer: Option D

Explanation:

A char is really a 16-bit integer behind the scenes, so it supports 216 (from 0 to 65535) values.

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