Language Enhancements

Question 0

When initialize variable from primitive type does new object is used?

Answer 0

No

Question 1

Using String in switch statement uses equals method to compare Strings

Answer 1

Yes

Question 2

The integral types byte short int long can be expressed using the binary number system…

Answer 2

Yes

(byte)0b00100001

Question 3

Using binary literals 0b or 0B is the same

Answer 3

Yes

Question 4

We can use any number of underscores _ anywhere between digits in numerical literals

Answer 4

Yes

Question 5

We can place underscore in adjacent to the decimal point literal

Answer 5

No 3.14_5555 is invalid

Question 6

We can place underscore character prior to F or L suffix

Answer 6

No

Question 7

int v = _90; is valid…

Answer 7

No

Question 8

Which classes can be used as part of try with resources block…

Answer 8

Those that implement AutoClosable interface

Question 9

The compiler can check the exact type of exception can be thrown and catch it in general Exception but declare it in the throws clause as specific types…

Answer 9

Yes

Question 10

Any object that implements …, which includes all objects which implement java.io.Closeable can be used as a resource.

Answer 10

java.lang.AutoCloseable

Question 11

The class BufferedReader, in Java SE 7 and later, implements the interface …

Answer 11

java.lang.AutoCloseable

Question 12

Using try with resources if an exception is thrown from both try and finally blocks the exception from try is thrown and the exception from finally is suppressed the opposite of prior to java 7

Answer 12

Yes

Question 13

Note that the close methods of resources are called in …

Answer 13

the opposite order of their creation.

Question 14

Note: A try-with-resources statement can have catch and finally blocks just like an ordinary try statement. In a try-with-resources statement, any catch or finally block is run after the resources declared have been closed.

Answer 14

Yes

Question 15

The following are the methods and constructors in Throwable that support chained exceptions….

Answer 15

Throwable getCause()
Throwable initCause(Throwable)
Throwable(String, Throwable)
Throwable(Throwable)

Question 16

Note that it is a common mistake to forget the diamond operator
< > in the initialization expression, as in
Pair worldCup = new Pair (2010, “South Africa”); shows the compiler…

Answer 16

warning when you forget to use the diamond syntax.

Question 17

Compiler warning when you forget to use diamond syntax…

Answer 17

Yes

Question 18

subtyping does not work for generic parameters…

Answer 18

Yes

Question 19

type parameters for generics have a limitation: generic type parameters should match exactly for assignments. to overcome this subtyping problem, you can use wildcard types…

Answer 19

Yes

Question 20

You cannot instantiate a generic type using new operator. For example, assuming mem is a field, the following statement will result in a compiler error: T mem = new T(); // wrong usage - compiler error

Answer 20

Yes

Question 21

You can declare non-static fields of type T, but not of static fields of type T. For example, class X {   
T instanceMem;          // okay   
static T statMem;       // wrong usage - compiler error

Answer 21

Yes

Question 22

It is not possible to have generic exception classes; as a result, the following will not compile: 
class GenericException extends Throwable { } // wrong usage - compiler error

Answer 22

Yes

Question 23

To use collections like HashSet, you must override…

Answer 23

the hashCode() and equals() methods correctly.

Question 24

A class implementing this interface can be used for iterating with a for each statement…

Answer 24

Iterable

Question 25

In a Deque you can insert or remove elements from both the ends

Answer 25

Yes

Question 26

Note that Map hierarchy does not extend the Collection interface…

Answer 26

Yes

Question 27

You can traverse in both forward and reverse directions if a class implements the ….

Answer 27

ListIterator interface

Question 28

You can traverse over the container in the forward direction if a class implements the …

Answer 28

Iterator interface

Question 29

ArrayList Fast to search, but slow to insert or delete. Allows duplicates

Answer 29

Yes

Question 30

Methods in the Iterator Interface…

Answer 30

boolean hasNext() 
E next() 
void remove()

Question 31

Before we call remove on iterator we must call next

Answer 31

Yes

Question 32

Methods in the ListIterator Interface (in Addition to Iterator Methods…

Answer 32

boolean hasPrevious()
Element previous() 
int nextIndex() 
int previousIndex() 
void set(Element) 
void add(Element

Question 33

So, insertion and deletion is very fast in…

Answer 33

LinkedList

Question 34

The container classes store references to objects, so you cannot use primitive types with any of the collection classes. Since you have wrapper classes and auto-boxing, it is not a big problem—that is why you use Character instead of char here

Answer 34

Yes

Question 35

the methods hashCode() and equals() need to be consistent for a class. For practical purposes, ensure that you follow this one rule: the hashCode() method should return the same hash value for two objects if the equals() method returns true for them

Answer 35

Yes

Question 36

A Queue follows FIFO mechanism…

Answer 36

Yes

Question 37

The Deque interface was introduced in Java 6 in java.util.collection package

Answer 37

Yes

Question 38

Commonly Used Methods in the Deque Interface…

Answer 38

void addFirst(Element) 
void addLast(Element) 
Element removeFirst() 
Element removeLast() 
Element getFirst() 
Element getLast()

Question 39

Using deque, they do not raise exception on failure…

Answer 39

boolean offerFirst(Element)
 boolean offerLast(Element) 
Element pollFirst() 
Element pollLast() 
Element peekFirst() 
Element peekLast

Question 40

There are three concrete implementations of the Deque interface…

Answer 40

LinkedList, ArrayDeque, and LinkedBlockingDeque

Question 41

remember that you cannot add elements to the List returned by the Arrays.asList() method. But, you can make changes to the elements in the returned List, and the changes made to that List are reflected back in the array

Answer 41

Yes

Question 42

You use the extends keyword for both class type as well as an interface when specifying bounded types in generics. For specifying multiple base types, you use the & symbol. For example, in List, ? will match types, extending both

Answer 42

Yes

Question 43

An interface can be declared in a class or interface as inner…

Answer 43

Yes

Question 44

A rule of thumb is to use has-a and is-a phrases for composition and inheritance, respectively to assess when to use composition or inheritance…

Answer 44

Yes

Question 45

Class inheritance implies an is-a relationship, interface inheritance implies an is-like-a relationship, and composition implies a has-a relationship…

Answer 45

Yes

Question 46

Use inheritance when a subclass specifies a base class, so that you can exploit dynamic polymorphism. in other cases, use composition to get code that is easy to change and loosely coupled. in summary, favor composition over inheritance…

Answer 46

Yes

Question 47

In composition, the lifetime of the contained object and the container object is the same, whereas that is not the case with aggregation. For example, a computer object and a CPU object share a composition relationship, while a library object and a book object share an aggregation relationship…

Answer 47

Yes