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Java Methods, Loops, Keywords (Interview Questions)

  1. Which declaration of the main method below would allow a class to be started as a standalone program. Select the one correct answer. 
    A. public static int main(char args[]) 
B. public static void main(String args[]) 
C. public static void MAIN(String args[]) 
D. public static void main(String args) 
E. public static void main(char args[])


    Answer: B
    public static void main(String [] args)
  2. What is the output when the following code is compiled and run?
    Select the three correct answers.
    public class Xyz {
 public static void main(String args[]) {
  for(int i = 0; i < 2; i++) {
   for(int j = 2; j>= 0; j--) {
    if(i == j) break;
     System.out.println("i=" + i + " j="+j);
    }
   }
  }
}


    a.	i=0 j=0 
b.	i=0 j=1 
c.	i=0 j=2 
d.	i=1 j=0 
e.	i=1 j=1 
f.	i=1 j=2 
g.	i=2 j=0 
h.	i=2 j=1 
i.	i=2 j=2


    Answer:c, b, f : In that order.
  3. What gets printed when the following code is compiled and run with the following command 
    java Test 2
    Select the one correct answer. 
    public class Test {
 public static void main(String args[]) { 
  Integer intObj=Integer.valueOf(args[args.length-1]);
   int i = intObj.intValue();
   if(args.length > 1) 
    System.out.println(i);
   if(args.length > 0)
    System.out.println(i - 1);
   else 
    System.out.println(i - 2);
 }
}


    A.	Test 
B.	Test -1 
C.	0 
D.	1 
E.	2


    Answer: D
  4. In Java SE17, what expression can be used to represent the number of elements in an array named arr ?

    Answer:
    In Java SE17, the number of elements in an array named `arr` can be determined by utilizing the `length` property of the array. The expression to represent this is written as `arr.length`. This property provides the total count of elements that the array can hold, which is set at the time of its creation and remains fixed throughout the array's lifetime.
    For example, if you have an array of integers named `arr`, the expression to find its size would be as follows: 
    int size = arr.length;

    This expression will store the number of elements in `arr` into the integer variable `size`.

  5. How would the number 5 be represented in hex using up-to four characters?

    Answer:
    In Decimal base 10 the number 5 is also 5 in Hex base 16.
    Decimal number (base 10) 5 is in Hexadecimal (base 16) also 5.
  6. Which of the following is a Java keyword. (Select the four correct answers.)
    1. extern
    2. synchronized
    3. volatile
    4. friend
    5. friendly
    6. transient
    7. this
    8. then


    Answer: b, c, f, g
    See the following link: Java Keywords and identifiers
  7. Is the following statement true or false.
    The constructor of a class must not have a return type.
    A. true
    B. false


    Answer:
    True
    If it has a return type, it is not a constructor, it is a method.
  8. What is the number of bytes used by Java primitive long?
    Select the one correct answer.
    The number of bytes is compiler dependent.
    a. 2
    b. 4
    c. 8
    d. 64

    Answer: d
    Explanation: The data type long supports 64-bit integer values whose values range from -(263) to 263 - 1.
  9. What is returned when the method substring (2, 4) is invoked on the string "example"?
    Include the answer in quotes as the result is of type String.

    Answer: 
    public class Test1 {
 public static void main(String[] args) {
  String s1=  "example";
  System.out.println(s1.substring (2, 4));
 s}
}

    "am"
  10. Which of the following is correct? Select the two correct answers.
    1. The native keyword indicates that the method is implemented in another language like C/C++.
    2. The only statements that can appear before an import statement in a Java file are comments.
    3. The method definitions inside interfaces are public and abstract. They cannot be private or protected.
    4. A class constructor may have public or protected keyword before them, nothing else.


    Answer: a, c
    Explanation:
    a) The native keyword is applied to a method to indicate that the method is implemented in native code using JNI.
    b) The method definitions inside an interface are public and abstract methods.
    3) Yes, a constructor can be private. There are different uses of this.
    One such use is for the singleton design anti-pattern, which I would advise against you using.
    Another, more legitimate use is in delegating constructors. You can have one constructor that takes many different options that is really an implementation detail, so you make it private, but then your remaining constructors delegate to it.

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