Language Fundamentals - General Questions Questions and Answers

Q: Which is a valid keyword in java?

interface is a valid keyword. 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.

Q: Which one of the following will declare an array and initialize it with five numbers?

Option B is the legal way to declare and initialize an array with five elements. 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.

Q: Which one is a valid declaration of a boolean?

Correct answer: boolean b3 = false;A boolean accepts only the literals true and false. Java performs no conversion between numbers and booleans, so 0 is not accepted - the C idiom of zero meaning false does not carry over. 'false' in single quotes is a char literal and in any case too long to be one, Boolean.false() is not a method, and no is an undeclared identifier.

Q: Which is a reserved word in the Java programming language?

The word "native" is a valid keyword, used to modify a method declaration. Option A, D and E are not keywords. Option C is wrong because the keyword for subclassing in Java is extends, not 'subclasses'.

Q: Which is a valid declarations of a String?

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).

11.

Which three are legal array declarations?

1.int [] myScores [];

2.char [] myChars;

3.int [6] myScores;

4.Dog myDogs [];

5.Dog myDogs [7];

A.1, 2, 4
B.2, 4, 5
C.2, 3, 4
D.All are correct.

Answer: A

(1), (2), and (4) are legal array declarations. With an array declaration, you can place the brackets to the right or left of the identifier. Option A looks strange, but it's perfectly legal to split the brackets in a multidimensional array, and place them on both sides of the identifier. Although coding this way would only annoy your fellow programmers, for the exam, you need to know it's legal.

(3) and (5) are wrong because you can't declare an array with a size. The size is only needed when the array is actually instantiated (and the JVM needs to know how much space to allocate for the array, based on the type of array and the size).

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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: C

(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.

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13.

Which is a valid keyword in java?

A.interface
B.string
C.Float
D.unsigned

Answer: A

interface is a valid keyword.

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.

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14.

Which one of the following will declare an array and initialize it with five numbers?

A.Array a = new Array(5);
B.int [] a = {23,22,21,20,19};
C.int a [] = new int[5];
D.int [5] array;

Answer: B

Option B is the legal way to declare and initialize an array with five elements.

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.

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15.

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: C

Correct answer: boolean b3 = false;

A boolean accepts only the literals true and false. Java performs no conversion between numbers and booleans, so 0 is not accepted - the C idiom of zero meaning false does not carry over. 'false' in single quotes is a char literal and in any case too long to be one, Boolean.false() is not a method, and no is an undeclared identifier.

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16.

Which is a reserved word in the Java programming language?

A.method
B.native
C.subclasses
D.reference
E.array

Answer: B

The word "native" is a valid keyword, used to modify a method declaration.

Option A, D and E are not keywords. Option C is wrong because the keyword for subclassing in Java is extends, not 'subclasses'.

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17.

Which one of these lists contains only Java programming language keywords?

A.class, if, void, long, Int, continue
B.goto, instanceof, native, finally, default, throws
C.try, virtual, throw, final, volatile, transient
D.strictfp, constant, super, implements, do
E.byte, break, assert, switch, include

Answer: B

All the words in option B are among the 49 Java keywords. Although goto reserved as a keyword in Java, goto is not used and has no function.

Option A is wrong because the keyword for the primitive int starts with a lowercase i.

Option C is wrong because "virtual" is a keyword in C++, but not Java.

Option D is wrong because "constant" is not a keyword. Constants in Java are marked static and final.

Option E is wrong because "include" is a keyword in C, but not in Java.

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18.

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: A

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).

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