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- Question
Which one is a valid declaration of a boolean?
Options- A. boolean b1 = 0;
- B. boolean b2 = 'false';
- C. boolean b3 = false;
- D. boolean b4 = Boolean.false();
- E. boolean b5 = no;
- Correct Answer
- boolean b3 = false;
ExplanationA boolean can only be assigned the literal true or false. - 1. Which is the valid declarations within an interface definition?
Options- A. public double methoda();
- B. public final double methoda();
- C. static void methoda(double d1);
- D. protected void methoda(double d1); Discuss
- 2. Which three piece of codes are equivalent to line 3?
- final int k = 4;
- public int k = 4;
- static int k = 4;
- abstract int k = 4;
- volatile int k = 4;
- protected int k = 4;
public interface Foo { int k = 4; /* Line 3 */ }
Options- A. 1, 2 and 3
- B. 2, 3 and 4
- C. 3, 4 and 5
- D. 4, 5 and 6 Discuss
- 3. What is the numerical range of a char?
Options- A. -128 to 127
- B. -(215) to (215) - 1
- C. 0 to 32767
- D. 0 to 65535 Discuss
- 4. Which is a valid declarations of a String?
Options- A. String s1 = null;
- B. String s2 = 'null';
- C. String s3 = (String) 'abc';
- D. String s4 = (String) '\ufeed'; Discuss
- 5. Which is a valid keyword in java?
Options- A. interface
- B. string
- C. Float
- D. unsigned Discuss
- 6. Which one of the following will declare an array and initialize it with five numbers?
Options- A. Array a = new Array(5);
- B. int [] a = {23,22,21,20,19};
- C. int a [] = new int[5];
- D. int [5] array; Discuss
- 7. Which three are valid declarations of a float?
- float f1 = -343;
- float f2 = 3.14;
- float f3 = 0x12345;
- float f4 = 42e7;
- float f5 = 2001.0D;
- float f6 = 2.81F;
Options- A. 1, 2, 4
- B. 2, 3, 5
- C. 1, 3, 6
- D. 2, 4, 6 Discuss
Language Fundamentals problems
Search Results
Correct Answer: public double methoda();
Explanation:
Option B is wrong. The final modifier means that this method cannot be constructed in a subclass. A final method cannot be abstract.
Option C is wrong. static is concerned with the class and not an instance.
Option D is wrong. protected is not permitted when declaring a method of an interface. See information below.
Member declarations in an interface disallow the use of some declaration modifiers; you cannot use transient, volatile, or synchronized in a member declaration in an interface. Also, you may not use the private and protected specifiers when declaring members of an interface.
Correct Answer: 1, 2 and 3
Explanation:
(1), (2) and (3) are correct. Interfaces can have constants, which are always implicitly public, static, and final. Interface constant declarations of public, static, and final are optional in any combination.
Correct Answer: 0 to 65535
Explanation:
Correct Answer: String s1 = null;
Explanation:
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).
Correct Answer: interface
Explanation:
Option B is wrong because although "String" is a class type in Java, "string" is not a keyword.
Option C is wrong because "Float" is a class type. The keyword for the Java primitive is float.
Option D is wrong because "unsigned" is a keyword in C/C++ but not in Java.
Correct Answer: int [] a = {23,22,21,20,19};
Explanation:
Option A is wrong because it shows an example of instantiating a class named Array, passing the integer value 5 to the object's constructor. If you don't see the brackets, you can be certain there is no actual array object! In other words, an Array object (instance of class Array) is not the same as an array object.
Option C is wrong because it shows a legal array declaration, but with no initialization.
Option D is wrong (and will not compile) because it declares an array with a size. Arrays must never be given a size when declared.
Correct Answer: 1, 3, 6
Explanation:
(2), (4),and (5) are all doubles.
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