Java 8 Interview Questions and Answers
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Ques 21. Provide some examples of Terminal operations.
Example of Terminal operations are:
- forEach
- toArray
- reduce
- collect
- min
- max
- count
- anyMatch
- allMatch
- noneMatch
- findFirst
- findAny
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Ques 22. Given the list of numbers, remove the duplicate elements from the list.
See the following code:
Integer[] arr=new Integer[]{1,2,3,4,3,2,4,2};
List<Integer> listWithDuplicates = Arrays.asList(arr);
Set<Integer> setWithoutDups = listWithDuplicates.stream().collect(Collectors.toSet());
setWithoutDups.forEach((i)->System.out.print(" "+i));
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Ques 23. Difference between Stream findFirst() and findAny().
- findFirst will always return the first element from the stream whereas findAny is allowed to choose any element from the stream.
- findFirst has deterministic behavior whereas findAny is nondeterministic behavior.
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Ques 24. What is consumer function interface?
It is a functional interface defined in java.util.function package. It contains an abstract accept() and a default andThen() method. It can be used as the assignment target for a lambda expression or method reference.
Consumer is single argument functional interface which does not return any value.public static void main(String[] args) {
Consumer<String> consumerString = s->System.out.println(s);
consumerString.accept("John");
}
We have created consumer object which takes String object as input and print it. It is simple use of Consumer interface to print String.
Output:
John
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Ques 25. What is predicate function interface?
Predicate is single argument function which returns true or false. It has test method which returns boolean. Usually, it used to apply in a filter for a collection of objects.
public static void main(String[] args) {
Predicate<Integer> predicate = i -> i > 100;
boolean greaterCheck = predicate.test(200);
System.out.println("is 200 greater than 100: "+greaterCheck);
}
Output:
is 200 greater than 100: true
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