Core java interview Questions You'll Most Likely Be Asked (Second Edition)

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What is StringJoiner? Explain with a code sample.
Answer:
StringJoiner is a new class added by Java 8. It helps to
concatenate Strings separated by a delimiter and having a prefix
and suffix. The following code demonstrates this:
StringJoiner strJoiner = new StringJoiner(“–”,”[“,”]”);
//Line 1
strJoiner.add(“cat”); //Line 2
strJoiner.add(“dog”); //Line 3
strJoiner.add(“mouse”); //Line 4
System.out.println(strJoiner); //Line 5
This code creates a StringJoiner. It uses the colon symbol(:)
as the delimiter and square brackets ([]) as the prefix and suffix. It
then invokes the add() method with some String values. So this
code prints the following output:
[cat:dog:mouse]
Explain the differences between the Comparator.reverse
and Comparator.reverseOrder methods.
Answer:
Both the Comparator.reversed and
Comparator.reverseOrder are methods added by Java 8 to
the Comparator interface. Both help in sorting a Collection in
reverse order. However, there are some differences between the
two as follows:
Comparator.reversed is a default method while
Comparator.reverseOrder is a static method.

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260.
The Comparator.reversed requires a comparator to be
present. It simply reverses that comparator. The
Comparator.reverseOrder does not require a
Comparator to be present. It directly returns a comparator that
sorts in reverse order.
The Comparator.reversed returns a Comparator that
imposes the reverse ordering of the Comparator on which it is
invoked. The Comparator.reverseOrder on the other
hand returns a Comparator that imposes the reverse of the
natural ordering of the elements in the Collection.
Identify the error in the code below and explain what