Java Bank

1. What is the base class of all classes ?
 Answer: java.lang.Object

2. What type of language is Java?
Answer: Pure Object Oriented

3. Which package in Java is automatically imported ( imported implicitly ) ?
Answer: java.lang

4. Which one of the following is a valid boolean declaration ?
Answer: boolean b = false;

5. What is the numerical range of a char?
Answer: 0 to 65535

6. What does the following code do ?

• public static void main(String[] args)
• {
•    int a[] = { 1, 3, 5, 7, 9 };
•    for(int b:a)
•        System.out.println(b);
• }
• Answer: Print the values of a
• Explanation: ':' is 'for each' operator and is special in Java.
• 
  
• 7. Predict the output
• public static void main(String[] args)
• {
•      int a;      System.out.println(a); 
• }
• Answer: None of the above (neither 0 nor garbage) 
• Explanation: This produces 'variable not initialized' error   
• 
  
• 8. Predict the output
• public static void main(String[] args)
• {
•     String str = "Sona";
•     System.out.println(str[1]);
• } 
• Answer: Error
• Explanation: The [] operator is available only for array data types. String is a class.
• 
  
• 9. How will you find the number of elements in an array ( of any data type ) in Java ?
• Answer: Using the length member of the array object
• 
  
• 10. What will you use to find the length of a String in Java.
• Answer: length() method.
• 
  
• 11. How to you compare two String objects in Java ?
• Answer: s1.equals(s2)
• Explanation: The equals method available in the String class makes the comparison between the String objects and returns a boolean. 
• 
  
• 12. How do you force garbage collection in Java ?
• Answer: System.gc();
• Explanation: Though Java supports automatic garbage collection, manually garbage collection is also possible by calling gc() method of System class.
• 
  
• 13. How can you achieve multiple inheritance in Java ?
• Answer: Through interface it can be achieved
• Explanation: Not only through interface, but also through multi-level inheritance, multiple inheritance is indirectly achievable in Java.
• 
  
• 14. What is the base class of the class Object ?
• Answer: null
• Explanation: All the classes are derived from the Object class, whereas the Object class has no super class. In other words, Object class is not derived from any other class.
• 
  
• 15. How do you redirect the output to a file in Java ?
• Answers: Use PrintStream object everywhere instead of System.out,
•                  Pass the PrintStream object to setOut method of System class.
• Explanation: Both the answers are actually correct. But, the most general thing is the latter, because, if we want the output in console, we can comment just one statement.

16. Which import statment will you use to simply call pow() instead of Math.pow() ?Answer: import static java.lang.Math.*;Explanation: This statement imports all static methods available in the Math class from java.lang package.

17. What is the use of finalize() method ?Answer: It acts as a destructor

18. What is the purpose of using final modifier?

• Answer: To make the variable constant

19. Why is finally keyword used?

• Answer: For executing statements after try & catch blocks
• Explanation: The finally block is executed even when an exception occurs (after executing catch block).

20. Is overloading supported in Java?

• Answer: Only method overloading is supported

21. Find the output of the following program  

public class Test 

{ 

   public static void main(String[] args) 

  { 

     System.out.printf(“%d”, 7); 

  } 

}
Answer: 7

22. Which is the fastest loop?

Answer: for – each

23. Predict the output
public class Test 

{ 

    public static void main(String[] args) 

    { 

         System.out.println(“2 + 2 = ” + 2 + 2); 

    } 

}
Answer: 2 + 2 = 22

Explanation: Here, string concatenation takes place and not addition. The statement should be corrected as System.out.println("2 + 2 = " + (2 + 2)); to display the result 2 + 2 = 4.

24. What is 'if' ?

Answer: Keyword

Explanation: 

'if' is a keyword, which is used for writing conditional statements.

For example:

'if' is a keyword.

'if(condition)

{

  true_statements;

}' is a conditional statement (which uses 'if' keyword).

25. What was the initial name of Java?

Answer: Oak

26. Which among the following are used for handling exceptions in Java ?

Answer: Both try and catch

27. What is the efficient way of sorting arrays?

Answer: sort() method available in the Arrays class

28. What is the purpose of final class ?

Answer: final class can not be inherited

29. What is the equivalent of Macros of C/C++ in Java ?

Answer: Interface

30. Predict the output. 

public class Main 

{ 

    public static void main(String[] args) 

    { 

         Integer i = 3; 

         System.out.println(i); 

    } 

}

Answer: 3

31. Predict the outputpublic class A {    void A()     {         System.out.println("Class A");     }     public static void main(String[] args)     {         new A();     } }Answer: No outputExplanation: void A() is a method as it has a return type. Most of you have will assume void A() as a constructor and answer 'Class A'. It will be a constructor only if the prototype is A() without a return type.

32. What is the efficient way of copying an array 'b' to a new array 'a' ?int b[] = { 1, 2, 3, 4, 5}

• Answer: copy() method available in the Arrays class
• Explanation: 
• int[] a = b; makes a reference and when you change content of 'b', the content of 'a' will also change.
• for(int i = 0; i < b.length; i++) { a[i] = b[i] };. This is not an efficient way
• copy() method available in the Arrays class is used to copy an array.

33. What is the purpose of final method ?

• Answer: final method can not be overridden

34. Which among the following is a static method?Answer: Both parseInt() and pow()Explanation: We call both methods without creating object.

35. Predict the output. class Inherit {    public Inherit(int i)    {        System.out.println("Value = " + i);     }}public class Main extends Inherit {     public static void main(String[] args)      {          super(7);      } }

• Answer: Value = 7
• Explanation: super() calls the base class constructor.