Interview Questions and Answers - Order By Newest Q71. What will be the output of this code ? Set mySet = new TreeSet(); mySet.add("4567"); mySet.add("5678"); mySet.add("6789"); for(String s: mySet){ System.out.println(s); }
Ans. 4567 5678 6789 Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   set   treeset   coding   code Q72. public enum Day { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY } public class Test { Set mySet = new HashSet(); mySet.add(Day.MONDAY); mySet.add(Day.SUNDAY); mySet.add(Day.SATURDAY); for(Day d: mySet){ System.out.println(d); } }
Ans. SUNDAY MONDAY SATURDAY Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  enum   set   collections   hashset   coding   code Try 3 Question(s) Test Q73. How is HashSet maintained in memory by Java ? Core Java
Ans. HashSet is maintained as HashMap by Java with values of the HashSet as Keys of the HashMap and value of the HashMap as the constant PRESENT. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  ebay  java   collections   hashset   hashmap expert Q74. What is ConcurrentLinkedDeque ? Core Java
Ans. It's a Collections concrete class that provides implementation of a Double Ended queue that allows concurrent insertion, removal, and access operations that can be executed safely across multiple threads. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   queue   deque   concurrent collections Q75. What is CopyOnWriteArrayList ?
Ans. Its a type of ArrayList in which all Write operations , i.e add and set are performed by creating a new copy. This array never changes during the lifetime of the iterator, so it never throws ConcurrentModificationException Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   list   arraylist   copyonwritearraylist   ConcurrentModificationException Asked in 1 Companies Q76. What are the advantages and disadvantages of CopyOnWriteArrayList ? Core Java
Ans. This collections class has been implemented in such a manner that it can never throw ConcurrentModificationException. As it performs update and write operations by creating a new copy of ArrayList, It's slower compared to ArrayList. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   list   arraylist   copyonwritearraylist   advantages-disadvantages   ConcurrentModificationException Asked in 4 Companies Expert Q77. Name few Concurrent Collection Classes ?
Ans. ConcurrentHashMap ConcurrentLinkedDeque ConcurrentLinkedQueue ConcurrentMap ConcurrentNavigableMap ConcurrentSkipListMap ConcurrentSkipListSet Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   concurrent collections Q78. Name few Collections Map implementations ?
Ans. AbstractMap ConcurrentHashMap ConcurrentSkipListMap EnumMap HashMap IdentityHashMap LinkedHashMap SystemFlavorMap TreeMap WeakHashMap Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   map Q79. Name few interfaces that extends Collection Interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-interfaces-that.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   collection interface Q80. Name few classes that extends Collections class ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-inherit.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   collections class Q81. Name few abstract classes of Java collections framework ?
Ans. http://www.buggybread.com/2015/02/java-collections-abstract-classes.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections Q82. Name few classes that implement Set interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_78.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   set Q83. Name few classes that implement iterable interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_45.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   iterable Q84. Name few classes that implement Map interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_82.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   map Q85. Name few classes that implement List interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_35.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   list Q86. Name few classes that implement Queue interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_1.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections.queue Q87. Name few classes that implement Collection interface ?
Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   collection interface Q88. Name few Hash collections classes and interfaces ?
Ans. http://www.buggybread.com/2015/01/java-hash-collections-classes-and.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   hash collections Q89. Name few Queue classes and interfaces ?
Ans. http://www.buggybread.com/2015/01/java-collections-queue-classes-and.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   queue Q90. What are few iterator classes provided by Java ?
Ans. http://www.buggybread.com/2015/01/java-iterator-classes-and-interfaces.html Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   iterator Q91. Which sorting algorithm is used by Collections.sort() in Java ? Core Java
Ans. The sorting algorithm is a modified mergesort. This algorithm offers guaranteed n log(n) performance. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   algorithm   collections   collections.sort   sorting algorithm expert Try 1 Question(s) Test Q92. Difference between HashMap and WeakHashMap ?
Ans. WeakHashMap uses weak reference for keys, which means if the key object doesn't have any reference then both key/value mapping will become eligible for garbage collection. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   hashmap   weakhashmap   difference between   garbage collection   ebay Q93. Which tree is used to implement TreeMap in Java?
Ans. Red Black Tree Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   treemap   map expert Q94. What is collision in hash collections ? Core Java
Ans. Collision is the situation when two different elements have the same Hash Code. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  java   collections   collision   hashcode  hash code   hash collections   ebay Asked in 1 Companies intermediate   frequent Q95. What will the following code result ? List> intList = new ArrayList>(); intList.add(Optional.empty()); intList.add(Optional.of(2)); intList.add(Optional.of(3)); intList.add(Optional.of(4)); System.out.println(intList.get(null));
Ans. Compile time error at last line as the get method expect argument of type native int. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  arraylist   list   coding   collections Q96. What will the following code result ? Will it compile ? List> intList = new ArrayList>(); intList.add(Optional.empty()); intList.add(Optional.of(2)); intList.add(Optional.of(3)); intList.add(Optional.of(4)); System.out.println(intList.get((Integer)null));
Ans. Yes but the last line will throw NullPointerException upon execution. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  collections   arraylist   list   coding Q97. Do you know of any facility to convert between Scala and Java Util Collections ? Scala
Ans. We can use JavaConversions which is a part of Scala Library. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  scala   scala collections   java collections Q98. If we add Enum constants to a sorted collection ( Treemap , TreeSet ), What will be the order in which they will be maintained ? a. Sorted Collection wont maintain them in any order. b. Insertion Order c. Order in which constants are declared. d. Natural Sorting Order.
Ans. Order in which constants are declared. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  enum   collections   sorted collections   treemap   treeset   compareto   comparable   java Q99. Which interface does java.util.Hashtable implement ? a. List b. Set c. Collection d. Map Core Java
Ans. Map Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  hashtable   java   collections Q100. Which of the following is false ? a. HashMap came before HashTable. b. HashMap allows null values whereas Hashtable doesn’t allow null values. c. HashTable and HashMap allow Key-Value pairs. d. Hashtable is synchronized whereas HashMap is not.
Ans. HashMap came before HashTable. Help us improve. Please let us know the company, where you were asked this question : Like Discuss Correct / Improve  map   hashmap   hashtable   collection   java Try 2 Question(s) Test