Core Java - Interview Questions and Answers for 'Java8' | Search Interview Question

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Rarely asked as it was introduced with Java 8.

Q31. Difference between DoubleSummaryStatistics , IntSummaryStatistics and LongSummaryStatistics ?

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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Not frequently asked as it was introduced with Java 8.

Q32. What is StringJoiner ?

Core Java

Ans. StringJoiner is a util method to construct a string with desired delimiter. This has been introduced with wef from Java 8.

Sample Code

StringJoiner strJoiner = new StringJoiner(".");

strJoiner.add("Buggy").add("Bread");

System.out.println(strJoiner); // prints Buggy.Bread

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Not frequently asked as it was introduced with Java 8.

Q33. What is the use of Optional ?

Core Java

Ans. Optional is a good way to protect application from runtime nullPointerException in case the the absent value has been represented as null. So basically Optional class provides the type checking during compile time and hence will never result in NPE.

For ex -

List> intList = new ArrayList>();
intList.add(Optional.empty());
intList.add(Optional.of(new Employee("abc")));
intList.add(Optional.of(new Employee("xyz")));
intList.add(Optional.of(new Employee("123")));
System.out.println(intList.get(0).getName());

So Now , even when the first list element is empty, this code will never throw an NullPointerException.

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Rarely asked as it was introduced with Java 8.

Q34. Name few "Optional" classes introduced with Java 8 ?

Core Java

Ans. http://www.buggybread.com/2015/01/java-optional-classes-and-interfaces.html

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Rarely asked as it was introduced with Java 8.

Q35. What are the changes in Java.io in Java 8 ?

Core Java

Ans. http://www.buggybread.com/2015/01/migrating-to-java-8-new-classes_62.html

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Q36. Name few Java Util classes introduced with Java 8 ?

Core Java

Ans. http://www.buggybread.com/2015/01/migrating-to-java-8-new-classes_25.html

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Rarely asked as it was introduced with Java 8.

Q37. Name few java.lang classes introduced with Java 8 ?

Core Java

Ans. http://www.buggybread.com/2015/01/migrating-to-java-8-new-classes.html

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Rarely asked as it was introduced with Java 8.

Q38. What is DocLint in Java 8 ?

Core Java

Ans. DocLint Provide a means to detect errors in Javadoc comments early in the development cycle and in a way that is easily linked back to the source code.

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Rarely asked as it was introduced with Java 8.

Q39. What are the errors identified by DocLint ?

Core Java

Ans. Bad syntax, such as unescaped characters or unmatched parentheses

Bad HTML, such as invalid or missing tags or attributes

Bad references, such as referencing a non-existent type with @see

Accessibility errors, such as a missing summary or caption from a table

Missing info, such as an undocumented parameter

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Rarely asked as it was introduced with Java 8.

Q40. Which keyword specify that a variable is effectively final ? a. final b. No Keyword c. Both of the above d. None of the above

Core Java

Ans. No Keyword

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Rarely asked as it was introduced with Java 8.

Q41. Which of the following has been introduced with Java 8 ? a. StringBuffer b. StringBuilder c. StringFilter d. StringJoiner

Core Java

Ans. StringJoiner

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