Core Java - Interview Questions and Answers for 'Double' | Search Interview Question

Core Java - Interview Questions and Answers for 'Double' - 8 question(s) found - Order By Newest

Q1. What is the difference between float and double?

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.

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Q2. Have you ever faced problems with rounding decimal places and what were the reasons ?

Core Java

Ans. 1. The problem with double (x*100)/100 doesn't return exact x but few fractions lesser than x and then if you are using floor rounding , it makes a big difference

2. Rounding only after getting a result vs rounding each outcome of 2 operand make difference

3. Usage of inappropriate Rounding mode and Rounding scale.

4. Results with double and BigDecimal

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Rarely asked as it was introduced with Java 8.

Q3. Difference between DoubleSummaryStatistics , IntSummaryStatistics and LongSummaryStatistics ?

Core Java

Ans. They all does the same task i.e to compute statistical information on the stream of data. They differ by the way they store the statistical information as they expect a different data type of the values being used.

IntSummaryStatistics and LongSummaryStatistics expect non floating point values and hence stores the statistical information like min,max and sum as non floating values ( int or long ) whereas DoubleSummaryStatistics stores these information as floating value.

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Q4. Name few Double data types related classes and interfaces ?

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

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Q5. Which of the following data type you will prefer to store price - BigDecimal or Double ?

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

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Q6. Why calculations in float or Double sometimes gives unpredictable results ?

Core Java

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

For example - 0.1 is actually stored as
0.1000000000000000055511151231257827021181583404541015625

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Q7. What is the advantage of BidDecimal over Double ?

Core Java

Ans. BigDecimal provides more precision as compared to double.

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Q8. Math.round method rounds the decimal to an integer by stripping off the decimal places. How can we use the same method to keep only 2 decimal places

For example -

Math.round(12.3456) will return 12. What should we do to get 12.34 without using any other class or method.

Core Java

Ans. We can multiply the value by 100 and then use Math.round on that and then divide the result by 100

For example -

(Math.round(12.3456 * 100)) / 100

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