Java-201

Question 1

What is a type-safe?

Answer 1

It preserves a method arg to assign illegal values

Question 2

Are enums case senstives?

Answer 2

Yes

Question 3

How can we get the reference of enums?

Answer 3

Volume level = Volume.LOW

Volume level = Volume.valueOf(“LOW”);

Question 4

How many ways we can create threads

Answer 4

Two ways
By implementing the runnable in interface
And by extension to the athread class

Question 5

Does the time of execution of thread is guaranteed

Answer 5

Nope

Question 6

How many executors are defined by concurrency package

Answer 6

Executor
Executor service
Scheduled executor service

Question 7

Does - is allowed in identifiers?

Answer 7

Nope

Question 8

What is the regex pattern for space

Answer 8

\s+ (one or many)

Question 9

What are Streams?

Answer 9

They are wrapper for Collections and arrays

Question 10

Does Streams don’t store its elements.

Answer 10

No

Question 11

Are Streams immutable ?

Answer 11

Yes

Question 12

Are Streams reusable?

Answer 12

No, Once traversed , Need to create a new one

Question 13

Does Stream support indexes access its elements?

Answer 13

No

Question 14

Can stream execute its operations concurrently?

Answer 14

Yes need not to write MT

Question 15

Does Stream operations are lazy when possible?

Answer 15

Yes , when someone calls(Subscribe virtually)

Question 16

Tell me the IF for Stream?

Answer 16

java.util.stream.Stream interface

Question 17

Is java.util.stream.Stream interface works with primitives?

Answer 17

No

Question 18

Which streams is to work with primitives?

Answer 18

IntStream, LongStream,DoubleStream,

Question 19

How many ways the streams are created?

Answer 19

Using stream()
List list = Arrays.asList(new String[]{"dsd","sdsd"});

Stream stream = words.stream();

Using Stream.of()

Stream stream = Stream.of(“hello”,”hola”, “hallo”, “ciao”);

String[] words = {“hello”, “hola”, “hallo”, “ciao”};
Stream stream = Stream.of(words);

Question 20

How can we create IntStream?

Answer 20

int[] nums = {1,2,3,4}

Stream.of(nums)

Question 21

If we do Stream.of(nums).count(), why it prints 1?

Answer 21

It the no of objects inside

Question 22

What is the difference it makes to call a public nested class with the hosted class object?

Answer 22

that way nested class will have its value existed to hosted class, else without hosted object it will have its own existence

Question 23

Does Arrays class also has stream functions?

Answer 23

YEs int nums[] = {1,2,34,4}

Arrays.stream(nums).count()
Or
Use the primitive version
IntStream.of(nums).count()

Question 24

How can we generate a stream with Supplier?

Answer 24

With the Stream.generate function

static Stream generate(Supplier s)

Stream s = Stream.generate(new Supplier() { 
    public Double get() { 
        return Math.random(); 
    } 
}).limit(5);

Stream s = Stream.generate(() -> Math.random()).limit(5);

Or just:

Stream s = Stream.generate(Math::random).limit(5);

Question 25

What is java.util.stream package?

Answer 25

It contains classes for stream creation and manipulation

Question 26

What is collector in Stream?

Answer 26

it provides a mutable reduction operator and store the intermediate results, and then leads to final transformation

Question 27

Do we have Builder for Primitives ?

Answer 27

Yes IntStream, DoubleStream, LongStream.Builder like classes

Question 28

Are the Builders Immutable?

Answer 28

YEs

Question 29

What is the Collectors class in Stream?

Answer 29

It is an impl for Collector, which helps is providing various reduction operators

Question 30

What is StreamSupport?

Answer 30

Low-level class for manipulating and creating Stream

Question 31

What is the general sequence of a chain of operations in the stream?

Answer 31

collections > stream > filter(where caluse) > reduce(transform or narrowing again) > aggregate operations

int sum = widgets.stram().filter(p -> p.getColor() == RED).mapToInt(p -> b.getWeight()).sum();

Question 32

What is functional programming?

Answer 32

In which you do not work on an object , you work on applying a function to data. It does not support creating models

Question 33

In what ways Stream differ from collections?

Answer 33

No Storage, functional in nature, laziness( can apply lazy filtering, mapping, duplicate kind of operations) , Possible Unbounded : allows short-circuiting operation in finite time like limit(), findFirst, consumable: can only iterate only once , a new stream has to be created to consume again

Question 34

State ways in which a Stream can be consumed?

Answer 34

Collection: stream , parallelstream
Array : Arrays.stream()
Static method in Stream : Stream.of(Object[]), InteStream.range(int, int) & Stream.iterate(Object, UnaryOperator)
File : BufferredReader.lines()
File paths: Files class methids
Random : Random.ints

BitSet.stream(), Pattern.splitAsStream(java.lang.CharSequence), and JarFile.stream().

Question 35

Can enum be equated with == ?

Answer 35

Yes and correct way

Question 36

What are the two Stream operations?

Answer 36

Intermediate & terminal operations

Question 37

How is the Stream sequecne goes?

Answer 37

pipeline(Collection, array, a generator function, I/O channel) > internediate operations Stream.filer or Stream.map > terminal operations Stream.forEach or Stream.reduce

Question 38

If we do have break is switch, what will happen?

Answer 38

It will go to the next case automatically