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 Q1111. What is the problem with this code ?

class BuggyBread1 {

private BuggyBread2 buggybread2;

public static void main(String[] args){
try {
BuggyBread1 buggybread1 = new BuggyBread1();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
e.printStackTrace();
}
}
}		Core Java
Ans. Though we are trying to serialize BuggyBread1 object but we haven't declared the class to implement Serializable.

This will throw java.io.NotSerializableException upon execution.

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 Q1112. Will this code run fine if BuggyBread2 doesn't implement Serializable interface ?

class BuggyBread1 implements Serializable{
private BuggyBread2 buggybread2 = new BuggyBread2();

public static void main(String[] args){
try {
BuggyBread1 buggybread1 = new BuggyBread1();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
e.printStackTrace();
}
}
}		Core Java
Ans. No, It will throw java.io.NotSerializableException.

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 Q1113. Will this code work fine if BuggyBread2 doesn't implement Serializable ?

class BuggyBread1 extends BuggyBread2 implements Serializable{
private int x = 5;

public static void main(String[] args){
try {
BuggyBread1 buggybread1 = new BuggyBread1();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
e.printStackTrace();
}
}
}		Core Java
Ans. Yes.

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   Like         Discuss         Correct / Improve     java   io   file   fileio   coding   code   serialization   yesno  file handling

 Q1114. Will this code Work ? If not , Why ?

java.util.Calendar c = new java.util.Calendar();		Core Java
Ans. No. It gives the error "Cannot Instantiate the type Calendar". Calendar is an abstract class and hence Calendar object should be instantiated using Calendar.getInstance().

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   Like         Discuss         Correct / Improve     java   date   calendar   abstract class   yes-no

 Q1115. 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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 Q1116. 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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 Q1117. 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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 Q1118. 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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 Q1119. 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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 Q1120. 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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 Q1121. 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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 Q1122. 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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 Q1123. What's wrong with this code ?

public static void main(String[] args) {
String regex = "(\\w+)*";
String s = "Java is a programming language.";

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(s);
while (matcher.next()) {
System.out.println("The e-mail id is: " + matcher.group());
}
}		Core Java
Ans. matcher.find() should have been used instead of matcher.next() within while.

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   Like         Discuss         Correct / Improve     java   regex   pattern.matcher   java.util   coding   code

 Q1124. Which methods of the Pattern class have equivalent methods in the String class? Core Java
Ans. split() and macthes()

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 Q1125. 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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 Q1126. What is comparator interface used for ?Core Java
Ans. The purpose of comparator interface is to compare objects of the same class to identify the sorting order. Sorted Collection Classes ( TreeSet, TreeMap ) have been designed such to look for this method to identify the sorting order, that is why class need to implement Comparator interface to qualify its objects to be part of Sorted Collections.

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   Like         Discuss         Correct / Improve     java   collections   treemap   treeset   comparator     Asked in 2 Companies      Intermediate
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 Q1127. Which are the sorted collections ?Core Java
Ans. TreeSet and TreeMap

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   Like         Discuss         Correct / Improve     java   collections   treemap   treeset   basic interview question      basic        frequent

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.
  Q1128. 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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   Like         Discuss         Correct / Improve     java   collections   hashcode  hash code   equals   collections     Asked in 44 Companies      intermediate        frequent
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 Q1129. 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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  Q1130. What do you mean by "Java is a statically typed language" ?Core Java
Ans. It means that the type of variables are checked at compile time in Java.The main advantage here is that all kinds of checking can be done by the compiler and hence will reduce bugs.

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  Q1131. Can we have null keys in TreeMap ?Core Java
Ans. No, results in exception.

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 Q1132. Can value be null in TreeMap ?Core Java
Ans. Yes.

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 Q1133. What is a ConcurrentHashMap ?Core Java
Ans. ConcurrentHashMap is a hashMap that allows concurrent modifications from multiple threads as there can be multiple locks on the same hashmap.

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 Q1134. Why are Getter and Setter better than directly changing and retrieving fields ?

or

What is the significance of variable hiding in Java ?

or

Why it's preferred to keep variables private and allow their access through getter and setter methods ?		Core Java
Ans. 1. Methods can participate in runtime polymorphism whereas member variables cannot.

For example -

Vehicle vehicle = new Car();

car.getObjVariable();// will return variable defined in Car

whereas

car.variable

will return the variable from Car class irrespective of the object it holds.

2. Validations can be performed before setting the variables.

3. If the input format changes or some other value or calculated value needs to be returned , that can be absorbed by making change ( wrapping ) in the setter and getter. By this the call to method from outside or interface to the object will remain the same.

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  Q1135. Can we overload main method in Java ?Core Java
Ans. Yes, but the overloaded main methods without single String[] argument doesn't get any special status by the JVM. They are just another methods that needs to be called explicitly.

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 Q1136. 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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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q1137. What is the difference between ArrayList and LinkedList ?Core Java
Ans. Underlying data structure for ArrayList is Array whereas LinkedList is the linked list and hence have following differences -

1. ArrayList needs continuous memory locations and hence need to be moved to a bigger space if new elements are to be added to a filled array which is not required for LinkedList.

2. Removal and Insertion at specific place in ArrayList requires moving all elements and hence leads to O(n) insertions and removal whereas its constant O(1) for LinkedList.

3. Random access using index in ArrayList is faster than LinkedList which requires traversing the complete list through references.

4. Though Linear Search takes Similar Time for both, Binary Search using LinkedList requires creating new Model called Binary Search Tree which is slower but offers constant time insertion and deletion.

5. For a set of integers you want to sort using quicksort, it's probably faster to use an array; for a set of large structures you want to sort using selection sort, a linked list will be faster.

  Sample Code for ArrayList

  Sample Code for LinkedList

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 Q1138. 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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Frequently asked these days as there are major changes in Java 8.
  Q1139. What are new features introduced with Java 8 ?Core Java
Ans. Lambda Expressions , Interface Default and Static Methods , Method Reference , Parameters Name , Optional , Streams, Concurrency.

  Sample Code for Lambda

  Sample Code for interface default

  Sample Code for Optional

  Sample Code for Streams

  Sample Code for java.time

  Sample Code for Predicate

  Sample Code for Consumer

  Sample Code for MapMerge

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   Like         Discuss         Correct / Improve     java   java8   technical lead   technical architect     Asked in 14 Companies      expert        frequent

Rarely asked as default methods have been introduced with Java 8.
 Q1140. Can we have a default method without a Body ?Core Java
Ans. No. Compiler will give error.

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