Core Java - Interview Questions and Answers for 'Data type' | Search Java Interview Question - javasearch.buggybread.com

Javasearch.buggybread.com

Search Interview Questions

3273 questions in repository.

There are more than 200 unanswered questions.
Click here and help us by providing the answer.

Have a video suggestion.
Click Correct / Improve and please let us know.

Submit Question

Core Java - Interview Questions and Answers for 'Data type' - 39 question(s) found - Order By Newest

Q1. What is casting?

^Anonymous

Ans. There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types casting type casting basic interview question Asked in 8 Companies basic frequent}

Q2. What are the Wrapper classes available for primitive types ?

^Anonymous

Ans. boolean - java.lang.Boolean
byte - java.lang.Byte
char - java.lang.Character
double - java.lang.Double
float - java.lang.Float
int - java.lang.Integer
long - java.lang.Long
short - java.lang.Short
void - java.lang.Void

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java5 data types wrapper classes adapter design pattern rare}

Q3. What are wrapper classes ?

^Anonymous

Ans. They are wrappers to primitive data types. They allow us to access primitives as objects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types wrapper classes Asked in 3 Companies basic frequent}

Q4. What is Generalization and Specialization in terms of casting ?

^{Admin
info@buggybread.com}

Ans. Generalization or UpCasting is a phenomenon where a sub class is prompted to a super class, and hence becomes more general. Generalization needs widening or up-casting. Specialization or DownCasting is a phenomenon where a super class is narrowed down to a sub class. Specialization needs narrowing or down-casting.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types casting type casting up casting type casting downcasting type casting generalization specialization Asked in 2 Companies}

Q5. Why Java is not considered pure OOP's language ?

Ans. There are 2 reasons for it.

1. Usage of Primitive types - Though Java provides classes for the primitive data types but as the usage of primitives is permissible, its considered unpure OOP's language.

2. Usage of Static members - Static members belong to the class and not objects and hence not considered fit for pure OOP's programming.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve oops object oriented programming object oriented language primitive data types Asked in 2 Companies}

Q6. What are the default or implicitly assigned values for data types in java ?

^Anonymous

Ans. boolean ---> false
byte ----> 0
short ----> 0
int -----> 0
long ------> 0l
char -----> /u0000
float ------> 0.0f
double ----> 0.0d
any object reference ----> null

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types default values}

Try 1 Question(s) Test

Q7. What is the difference between float and double?

^{Admin
info@buggybread.com}

Ans. Float can represent up to 7 digits accurately after decimal point, where as double can represent up to 15 digits accurately after decimal point.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types float double difference between basic interview question}

Q8. How do you prefer to store money values in your application ?

^{2016-11-15 09:38:25}

Ans. At Application level we use either Double or BigDecimal , preferably BigDecimal. At Database level we use Number with decimal precision 3.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data types}

Q9. Difference between long.Class and Long.TYPE ?

^Anonymous

Ans. They both represent the long primitive type. They are exactly the same.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types long.Class long.TYPE advanced expert rare}

Q10. What data type Variable can be used in a switch statement ?

^{Admin
info@buggybread.com}

Ans. Variables used in a switch statement can only be a byte, short, int, or char ( and String with Java 7 and above )

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java switch variable data type basic rare}

Q11. Variable of the boolean type is automatically initialized as?

^{Admin
info@buggybread.com}

Ans. The default value of the boolean type is false.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data type boolean initialization default object construction default constructor default value}

Q12. Name few classes that extends Number Class ?

^{Admin
info@buggybread.com}

Ans. http://www.buggybread.com/2015/02/java-util-classes-that-inherit-number.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types number class}

Q13. Name few Boolean classes and interfaces ?

^{Admin
info@buggybread.com}

Ans. http://www.buggybread.com/2015/01/java-data-types-double-classes-and_31.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types boolean}

Q14. Name few Double data types related classes and interfaces ?

^{Admin
info@buggybread.com}

Ans. http://www.buggybread.com/2015/01/java-data-types-double-classes-and.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types double}

Q15. Name few float data type related classes and interfaces ?

^{Admin
info@buggybread.com}

Ans. http://www.buggybread.com/2015/01/java-data-types-float-classes-and.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types float}

Q16. Name few Integer related classes and interfaces ?

^{Admin
info@buggybread.com}

Ans. http://www.buggybread.com/2015/01/java-data-types-integer-classes-and.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types integer}

Q17. Name few long data type related classes and interfaces ?

^{Admin
info@buggybread.com}

Ans. http://www.buggybread.com/2015/01/java-data-types-long-classes-and.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types long}

Q18. What is the difference between Data Type and Data Structure ?

^{Admin
info@buggybread.com}

Ans. Data type: a set of values together with operations on that type
Data structure: a physical implementation of a data type

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops data structure data type}

Q19. Is it correct to say that Interfaces are abstract data types ?

^{Admin
info@buggybread.com}

Ans. No.

Data Type holds data whereas Interface doesn't hold anything. Interface is a contract about how to communicate with the underlying Class.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java interface data type}

Q20. Do you see Class as a Data Type or Data Structure ?

^{Admin
info@buggybread.com}

Ans. Class can be better seen as Data Type. This could be implemented as a Data Structure too in some cases.

One thing worth understanding here is that Data type and Data structure are conceptual things. Class could be implementation of either of these.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops class data type data structure}

Q21. Which of the following data type you will prefer to store price - BigDecimal or Double ?

^{Admin
info@buggybread.com}

Ans. BigDecimal if memory and Performance is not critical concern, otherwise double.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types double bigdecimal}

Q22. Which takes more memory - float or Float ?

^{Admin
info@buggybread.com}

Ans. float is a native data type whereas Float is a class. A Float object will always take more memory than float variable as there are metadata overheads with the objects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data type float Asked in 3 Companies basic frequent}

Q23. What is the size of long data type ?

a. 16 bit
b. 32 bit
c. 64 bit
d. 128 bit

^Anonymous

Ans. 64 bit

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types}

Q24. What is the size of double type ?

a. 16 bit
b. 32 bit
c. 64 bit
d. 128 bit

^Anonymous

Ans. 64 bit

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types}

Q25. What is the size of short type ?

a. 8 bit
b. 16 bit
c. 32 bit
d. 128 bit

^Anonymous

Ans. 16 bit

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types}

Q26. What is ADT or Abtstract Data Type ?

Ans. ADT is a container which holds different types of objects with specifications.

For example - Stack, Array, Liked list, Tree

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data types abstract data types}

Q27. Why calculations in float or Double sometimes gives unpredictable results ?

^{2016-11-21 11:26:07}

Ans. Because the way float values are stored its not precise.

For example - 0.1 is actually stored as
0.1000000000000000055511151231257827021181583404541015625

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve double float data type basic frequent}

Q28. How does Java handle integer overflows and underflows?

^{2017-01-12 11:18:41}

Ans. It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve integer data types Asked in 1 Companies rare}

Q29. What are the different primitive data types in Java ?

^{2017-01-28 15:14:23}

Ans. boolean
byte
char
double
float
int
long
short
void

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data types primitive data types Asked in 1 Companies Basic}

Q30. Difference between int and short data types ?

^{2017-03-24 09:15:23}

Ans. Both holds numeric values. short is a 16-bit signed two's complement integer whereas int is a 32-bit signed two's complement integer.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data types short vs int}

Q31. What is widening and narrowing conversion in Java ?

^{2017-06-06 12:30:31}

Ans. Conversion means that the expression / literal / value of one type getting converted to other type.

Widening conversion is the conversion from Type A to Type B where B requires a wider space than A. For example - int to long, float to double, char to String etc. As the value moves to a wider space, there is no loss of information.

Narrowing conversion is the conversion from Type A to Type B where B requires a narrower space space than A. For example - int to long, float to double, char to String etc.As the value moves to a narrower space, there is a loss of information.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data type widening conversion narrowing conversion}

Q32. What is Boxing conversion ?

^{2017-06-06 12:31:36}

Ans. Boxing conversion converts expressions of primitive type to corresponding expressions of reference type.

For example

boolean to Boolean
long to Long
double to Double

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data type boxing wrapper classes}

Q33. Is String a Data type in Java ?

^{2017-06-18 18:04:10}

Ans. String is not a primitive type in java. Anything defined within double quotes like "abc" is an object of String class.

Sample Code for String

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve string data type Basic}

Q34. Are char,String and Char data types in java ?

^{2017-06-18 18:05:30}

Ans. char is a primitive data type. String is a class. Char is a wrapper class for primitive char.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve char string data type Basic}

Q35. What will be the output of following code and Why ?

int x = 5;
int y = 7;
float f = 5f;
float z = y / x * f;
System.out.println(z);

^{2017-07-23 20:00:12}

Ans. 5.0

operation between two ints generate int only. so 7/5 generates 1 and not 1.4. Multiplication between int and float generates float and hence

1 * 5.0 = 5.0

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve arithmetic calculation data types}

Q36. What do we mean by a Data Type ?

^{2017-08-08 15:15:15}

Ans. if you have similar type of data or objects or entities, then we can give them a type with unique name. And this name will be our Data type.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data type}

Q37. In the Following code which foo will get called.

foo(Integer i){
}

foo(String s){
}

public static void main(){
passing foo(null);
}

^{2018-01-21 17:16:39}

Ans. ambiguity error

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve code method function data types Asked in 1 Companies}

Q38. What is the advantage of BidDecimal over Double ?

^{2018-04-10 15:04:39}

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve BigDecimal Double data types}

Q39. What will be the output of following ?

public class BuggyBread {

   private int x;
   private Integer y;

   BuggyBread(int x,int y){};

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread(1,2);
      System.out.println(buggybread.x);
      System.out.println(buggybread.y);
   }
}    Reference

a. 0 0

b. 0 null

c. null 0

d. null null

Ans.b. 0 null