Difference between HashSet and HashMap?

They are entirely different constructs. A HashMap is an implementation of Map. A Map maps keys to values. The key look up occurs using the hash.

On the other hand, a HashSet is an implementation of Set. A Set is designed to match the mathematical model of a set. A HashSet does use a HashMap to back its implementation, as you noted. However, it implements an entirely different interface.

When you are looking for what will be the best Collection for your purposes, this Tutorial is a good starting place. If you truly want to know what’s going on, there’s a book for that, too.

Related Posts:

  1. HashSet vs. ArrayList
  2. How to sort a HashSet?
  3. What are the differences between a HashMap and a Hashtable in Java?
  4. When to use LinkedList over ArrayList in Java?
  5. Difference between Arrays.asList(array) and new ArrayList(Arrays.asList(array))
  6. Initialization of an ArrayList in one line
  7. How to sort an ArrayList?
  8. Exception in thread “main” java.lang.StackOverflowError
  9. Iterate through a HashMap [duplicate]
  10. Iterate through a HashMap [duplicate]
  11. Why is there no SortedList in Java?
  12. What is the significance of load factor in HashMap?
  13. How to update a value, given a key in a hashmap?
  14. Collision resolution in Java HashMap
  15. Hashtable, HashMap, HashSet , hash table concept in Java collection framework
  16. Printing HashMap In Java
  17. Java Hashmap: How to get key from value?
  18. Sorting HashMap by values
  19. FIFO based Queue implementations?
  20. HashMap get/put complexity
  21. Create a List of primitive int?
  22. How to convert int[] to Integer[] in Java?
  23. Change priorityQueue to max priorityqueue
  24. Collections.emptyMap() vs new HashMap()
  25. “Cannot create generic array of ..” – how to create an Array of Map?
  26. Sort a Map by values
  27. How to calculate the intersection of two sets?
  28. Why is a ConcurrentModificationException thrown and how to debug it
  29. Union or intersection of Java Sets
  30. Map of maps – how to keep the inner maps as maps?
  31. toring and Retrieving ArrayList values from hashmap
  32. What are the -Xms and -Xmx parameters when starting JVM?
  33. How to match “any character” in regular expression?
  34. Cannot make a static reference to the non-static method fxn(int) from the type Two
  35. How to implement a tree data-structure in Java?
  36. Difference between StringBuilder and StringBuffer
  37. How to create a sub array from another array in Java?
  38. “Missing return statement” within if / for / while
  39. A JNI error has occurred, please check your installation and try again in Eclipse x86 Windows 8.1
  40. Round a double to 2 decimal places
  41. com.atomikos.icatch.SysException: Error in init: Log already in use? tmlog in ./
  42. @ converted to %40 in HTTPPost request
  43. Global variables in Java
  44. Java implementation for Min-Max Heap?
  45. How can I convert a long to int in Java?
  46. Generic Interface
  47. Java Method Stubs
  48. What’s the purpose of META-INF?
  49. JVM Crash – “EXCEPTION_ACCESS_VIOLATION”
  50. How to connect to FTP over TLS/SSL (FTPS) server in Java
  51. How to check type of variable in Java?
  52. Spring boot – Request method ‘POST’ not supported. Tried everything
  53. Convert .class to .java
  54. What does Scanner input = new Scanner(System.in) actually mean?
  55. unused import statement for used ones in IntelliJ IDEA
  56. Unsigned long in Java
  57. Integer range when using 64bit jdk
  58. Removing whitespace from strings in Java
  59. what is this ANT build?
  60. org.glassfish.jersey.servlet.ServletContainer ClassNotFoundException
  61. How to get the current working directory in Java?
  62. What is a safe way to create a Temp file in Java?
  63. org.apache.jasper.JasperException: Unable to compile class for JSP:
  64. How do I parse command line arguments in Java?
  65. Missing method body, or declare abstract in Java
  66. java code is showing error. ( ‘;’,expected)
  67. Efficient swapping of elements of an array in Java
  68. local variables referenced from an inner class must be final or effectively final
  69. java.lang.NumberFormatException: empty String
  70. Java and Windows – error: illegal escape character
  71. How should I copy Strings in Java?
  72. Bank Account Java Program
  73. List of all special characters that need to be escaped in a regex
  74. No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?
  75. java.lang.ArithmeticException: / by zero
  76. ReferenceError: “alert” is not defined
  77. How to write an ArrayList of Strings into a text file?
  78. how to fix Cannot call sendRedirect() after the response has been committed?
  79. Correct way to add external jars (lib/*.jar) to an IntelliJ IDEA project
  80. difference between equals() and hashCode()
  81. Adding days to a date in Java
  82. The C# Shorthand getters and setters
  83. What’s the reason I can’t create generic array types in Java?
  84. Jackson with JSON: Unrecognized field, not marked as ignorable
  85. Create a two dimensional string array anArray[2][2]
  86. Convert double to Int, rounded down
  87. A beginner’s error (args[0]) [duplicate]
  88. Converting from byte to int in Java
  89. When/why to call System.out.flush() in Java
  90. Throwing multiple exceptions in Java
  91. fixing errors on a program to call methods in java
  92. How to Set the Background Color of a JButton on the Mac OS
  93. how to use drawArc()
  94. How to add RGB values into setColor() in Java?
  95. Can you write virtual functions / methods in Java?
  96. Creating video player using Java
  97. Can I override and overload static methods in Java?
  98. How can i fix this equals on primitive type(int)
  99. Split string into array of character strings
  100. intellij idea – Error: java: invalid source release 1.9

Leave a Comment