Interview Questions and Answers for 'Java' | Search Interview Question

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Q561. Is java.util.Date an abstract Class ? Is java.util.Calendar an abstract Class ?

Core Java

Ans. Date is not a abstract class whereas Calendar is.

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Q562. What will the following code print ?

java.util.Calendar c = java.util.Calendar.getInstance();
c.add(Calendar.MONTH, 5);
System.out.println(c.getTime());

Core Java

Ans. Date and Time after 5 months from now.

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Q563. Which of the following code is correct ?

a. DateFormat df = DateFormat.getInstance();
b. DateFormat df = DateFormat.getDateInstance();
c. DateFormat df = DateFormat.getInstance(DateFormat.FULL);
d. DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);

Core Java

Ans. All except c are correct.

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Q564. What is the use of parse method in DateFormat ?

Ans. It is used to parse String to get the Date Object with initialized date.

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Q565. Which of the following is not a valid java.util.Locale initialization ?

a. new Locale ()
b. new Locale ( String language )
c. new Locale ( String language , String country )

Core Java

Ans. a i.e new Locale()

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Q566. Which of the following is not a valid NumberFormat initialization ?

a. NumberFormat.getInstance()
b. NumberFormat.getDateInstance()
c. NumberFormat.getCurrencyInstance()
d. NumberFormat.getNumberInstance()

Core Java

Ans. b i.e NumberFormat.getDateInstance()

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Q567. What will the following code print ?

public static void main(String[] args){
Integer i1 = new Integer("1");
Integer i2 = new Integer("2");
Integer i3 = Integer.valueOf("3");
int i4 = i1 + i2 + i3;
System.out.println(i4);
}

Core Java

Ans. 6

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Q568. Which of the following syntax are correct ?a. LinkedList<Integer> l=new LinkedList<int>();b. List<Integer> l=new LinkedList<int>();c. LinkedList<Integer> l=new LinkedList<Integer>();d. List<Integer> l = new LinkedList<Integer>();

Core Java

Ans. All are correct.

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Q569. Which of the following code is correct ?

a. Date date = DateFormat.newInstance(DateFormat.LONG, Locale.US).parse(str);

b. Date date = DateFormat.newInstance(DateFormat.LONG, Locale.US).format(str);

c. Date date = DateFormat.getDateInstance(DateFormat.LONG, Locale.US).parse(str);

Core Java

Ans. c

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Q570. Which methods of the Pattern class have equivalent methods in the String class?

Core Java

Ans. split() and macthes()

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Q571. Can we compare Integers by using equals() in Java ?

Core Java

Ans. Yes for the Wrapper class Integer but not for the primitive int.

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Very Frequently asked. Favorite question in walkins and telephonic interviews. Usually among first few questions. Asked in different variants. Must know for intermediate and expert professionals.Among Top 10 frequently asked questions.

Q572. What is rule regarding overriding equals and hashCode method ?

Core Java

Ans. A Class must override the hashCode method if its overriding the equals method.

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Q573. What is the difference between Collection and Collections ?

Core Java

Ans. Collection is an interface whereas Collections is a utility class.

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Q574. Is Java a statically typed or dynamically typed language ?

Ans. Statically typed

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Q575. How can we reverse the order in the TreeMap ?

Ans. Using Collections.reverseOrder()

Map tree = new TreeMap(Collections.reverseOrder());

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Q576. TreeMap orders the elements on which field ?

Ans. Keys

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Q577. How TreeMap orders the elements if the Key is a String ?

Ans. As String implements Comparable, It refers to the String compareTo method to identify the order relationship among those elements.

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Q578. Can we add heterogeneous elements into TreeMap ?

Ans. No, Sorted collections don't allow addition of heterogeneous elements as they are not comparable.

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Q579. Will it create any problem if We add elements with key as user defined object into the TreeMap ?

Ans. It won't create any problem if the objects are comparable i.e we have that class implementing Comparable interface.

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Q580. Can we have null keys in TreeMap ?

Core Java

Ans. No, results in exception.

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Q581. Can value be null in TreeMap ?

Core Java

Ans. Yes.

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Q582. Which interface TreeMap implements ?

Ans. TreeMap implements NavigableMap, SortedMap, Serializable and Clonable.

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Frequently asked in Phone Interviews.

Q583. What are the various Auto Wiring types in Spring ?

Ans. By Name , By Type and Constructor.

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Q584. Is It Good to use Reflection in an application ? Why ?

Core Java

Ans. no, It's like challenging the design of application.

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Q585. Why is Reflection slower ?

Ans. Because it has to inspect the metadata in the bytecode instead of just using precompiled addresses and constants.

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Q586. How many SessionFactory and Session objects are created ?

Java EE

Ans. Single SessionFactory object and multiple session objects for opening different session. Hibernate creates new Session object per thread.

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Q587. What is the difference between int[] x; and int x[]; ?

Core Java

Ans. No Difference. Both are the acceptable ways to declare an array.

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Q588. What are the annotations used in Junit with Junit4 ?

Ans. @Test

The Test annotation indicates that the public void method to which it is attached can be run as a test case.

@Before

The Before annotation indicates that this method must be executed before each test in the class, so as to execute some preconditions necessary for the test.

@BeforeClass

The BeforeClass annotation indicates that the static method to which is attached must be executed once and before all tests in the class.

@After

The After annotation indicates that this method gets executed after execution of each test.

@AfterClass

The AfterClass annotation can be used when a method needs to be executed after executing all the tests in a JUnit Test Case class so as to clean-up the set-up.

@Ignores

The Ignore annotation can be used when you want temporarily disable the execution of a specific test.

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Q589. What is asynchronous I/O ?

Ans. It is a form of Input Output processing that permits other processing to continue before the I/O transmission has finished.

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Q590. If there is a conflict between Base Class Method definition and Interface Default method definition, Which definition is Picked ?

Ans. Base Class Definition.

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