LinkedHashSet<\/code> class of the Java collections framework provides functionalities of both the hashtable and the linked list data structure.<\/p>\n\n\n\nIt implements the\u00a0Set interface.<\/p>\n\n\n\n![\"Java](\"https:\/\/cdn.programiz.com\/sites\/tutorial2program\/files\/java-linkedhashset.png\")
<\/figure>\n\n\n\nElements of\u00a0LinkedHashSet<\/code>\u00a0are stored in hash tables similar to\u00a0HashSet.<\/p>\n\n\n\nHowever, linked hash sets maintain a doubly-linked list internally for all of its elements. The linked list defines the order in which elements are inserted in hash tables.<\/p>\n\n\n\n
\n\n\n\nCreate a LinkedHashSet<\/h2>\n\n\n\n
In order to create a linked hash set, we must import the java.util.LinkedHashSet<\/code> package first.<\/p>\n\n\n\nOnce we import the package, here is how we can create linked hash sets in Java.<\/p>\n\n\n\n
\/\/ LinkedHashSet with 8 capacity and 0.75 load factor\nLinkedHashSet<Integer> numbers = new LinkedHashSet<>(8, 0.75);\n<\/code><\/pre>\n\n\n\nHere, we have created a linked hash set named numbers<\/var>.<\/p>\n\n\n\nNotice, the part new LinkedHashSet<>(8, 0.75)<\/code>. Here, the first parameter is capacity<\/strong> and the second parameter is loadFactor<\/strong>.<\/p>\n\n\n\n- capacity<\/strong> – The capacity of this hash set is 8. Meaning, it can store 8 elements.<\/li>
- loadFactor<\/strong> – The load factor of this hash set is 0.6. This means, whenever our hash table is filled by 60%, the elements are moved to a new hash table of double the size of the original hash table.<\/li><\/ul>\n\n\n\n
Default capacity and load factor<\/strong><\/p>\n\n\n\nIt’s possible to create a linked hash set without defining its capacity and load factor. For example,<\/p>\n\n\n\n
\/\/ LinkedHashSet with default capacity and load factor\nLinkedHashSet<Integer> numbers1 = new LinkedHashSet<>();\n<\/code><\/pre>\n\n\n\nBy default,<\/p>\n\n\n\n
- the capacity of the linked hash set will be 16<\/li>
- the load factor will be 0.75<\/li><\/ul>\n\n\n\n
\n\n\n\nCreating LinkedHashSet from Other Collections<\/h2>\n\n\n\n
Here is how we can create a linked hash set containing all the elements of other collections.<\/p>\n\n\n\n
import java.util.LinkedHashSet;\nimport java.util.ArrayList;\n\nclass Main {\n public static void main(String[] args) {\n \/\/ Creating an arrayList of even numbers\n ArrayList<Integer> evenNumbers = new ArrayList<>();\n evenNumbers.add(2);\n evenNumbers.add(4);\n System.out.println(\"ArrayList: \" + evenNumbers);\n\n \/\/ Creating a LinkedHashSet from an ArrayList\n LinkedHashSet<Integer> numbers = new LinkedHashSet<>(evenNumbers);\n System.out.println(\"LinkedHashSet: \" + numbers);\n }\n}\n\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nArrayList: [2, 4]\nLinkedHashSet: [2, 4]\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nMethods of LinkedHashSet<\/h2>\n\n\n\n
The LinkedHashSet<\/code> class provides methods that allow us to perform various operations on the linked hash set.<\/p>\n\n\n\n
\n\n\n\nInsert Elements to LinkedHashSet<\/h2>\n\n\n\nadd()<\/code> – inserts the specified element to the linked hash set<\/li>addAll()<\/code> – inserts all the elements of the specified collection to the linked hash set<\/li><\/ul>\n\n\n\nFor example,<\/p>\n\n\n\n
import java.util.LinkedHashSet;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> evenNumber = new LinkedHashSet<>();\n\n \/\/ Using add() method\n evenNumber.add(2);\n evenNumber.add(4);\n evenNumber.add(6);\n System.out.println(\"LinkedHashSet: \" + evenNumber);\n\n LinkedHashSet<Integer> numbers = new LinkedHashSet<>();\n \n \/\/ Using addAll() method\n numbers.addAll(evenNumber);\n numbers.add(5);\n System.out.println(\"New LinkedHashSet: \" + numbers);\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet: [2, 4, 6]\nNew LinkedHashSet: [2, 4, 6, 5]\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nAccess LinkedHashSet Elements<\/h2>\n\n\n\n
To access the elements of a linked hash set, we can use the iterator()<\/code> method. In order to use this method, we must import the java.util.Iterator<\/code> package. For example,<\/p>\n\n\n\nimport java.util.LinkedHashSet;\nimport java.util.Iterator;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> numbers = new LinkedHashSet<>();\n numbers.add(2);\n numbers.add(5);\n numbers.add(6);\n System.out.println(\"LinkedHashSet: \" + numbers);\n\n \/\/ Calling the iterator() method\n Iterator<Integer> iterate = numbers.iterator();\n\n System.out.print(\"LinkedHashSet using Iterator: \");\n\n \/\/ Accessing elements\n while(iterate.hasNext()) {\n System.out.print(iterate.next());\n System.out.print(\", \");\n }\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet: [2, 5, 6]\nLinkedHashSet using Iterator: 2, 5, 6,\n<\/samp><\/code><\/pre>\n\n\n\nNote<\/strong>:<\/p>\n\n\n\nhasNext()<\/code> returns true<\/code> if there is a next element in the linked hash set<\/li>next()<\/code> returns the next element in the linked hash set<\/li><\/ul>\n\n\n\n
\n\n\n\nRemove Elements from HashSet<\/h2>\n\n\n\nremove()<\/code> – removes the specified element from the linked hash set<\/li>removeAll()<\/code> – removes all the elements from the linked hash set<\/li><\/ul>\n\n\n\nFor example,<\/p>\n\n\n\n
import java.util.LinkedHashSet;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> numbers = new LinkedHashSet<>();\n numbers.add(2);\n numbers.add(5);\n numbers.add(6);\n System.out.println(\"LinkedHashSet: \" + numbers);\n\n \/\/ Using the remove() method\n boolean value1 = numbers.remove(5);\n System.out.println(\"Is 5 removed? \" + value1);\n\n boolean value2 = numbers.removeAll(numbers);\n System.out.println(\"Are all elements removed? \" + value2);\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet: [2, 5, 6]\nIs 5 removed? true\nAre all elements removed? true\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nSet Operations<\/h2>\n\n\n\n
The various methods of the LinkedHashSet<\/code> class can also be used to perform various set operations.<\/p>\n\n\n\n
\n\n\n\nUnion of Sets<\/h3>\n\n\n\n
Two perform the union between two sets, we can use the addAll()<\/code> method. For example,<\/p>\n\n\n\nimport java.util.LinkedHashSet;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> evenNumbers = new LinkedHashSet<>();\n evenNumbers.add(2);\n evenNumbers.add(4);\n System.out.println(\"LinkedHashSet1: \" + evenNumbers);\n\n LinkedHashSet<Integer> numbers = new LinkedHashSet<>();\n numbers.add(1);\n numbers.add(3);\n System.out.println(\"LinkedHashSet2: \" + numbers);\n\n \/\/ Union of two set\n numbers.addAll(evenNumbers);\n System.out.println(\"Union is: \" + numbers);\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet1: [2, 4]\nLinkedHashSet2: [1, 3]\nUnion is: [1, 3, 2, 4]\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nIntersection of Sets<\/h3>\n\n\n\n
To perform the intersection between two sets, we can use the retainAll()<\/code> method. For example<\/p>\n\n\n\nimport java.util.LinkedHashSet;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> primeNumbers = new LinkedHashSet<>();\n primeNumbers.add(2);\n primeNumbers.add(3);\n System.out.println(\"LinkedHashSet1: \" + primeNumbers);\n\n LinkedHashSet<Integer> evenNumbers = new LinkedHashSet<>();\n evenNumbers.add(2);\n evenNumbers.add(4);\n System.out.println(\"LinkedHashSet2: \" + evenNumbers);\n\n \/\/ Intersection of two sets\n evenNumbers.retainAll(primeNumbers);\n System.out.println(\"Intersection is: \" + evenNumbers);\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet1: [2, 3]\nLinkedHashSet2: [2, 4]\nIntersection is: [2]\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nDifference of Sets<\/h3>\n\n\n\n
To calculate the difference between the two sets, we can use the removeAll()<\/code> method. For example,<\/p>\n\n\n\nimport java.util.LinkedHashSet;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> primeNumbers = new LinkedHashSet<>();\n primeNumbers.add(2);\n primeNumbers.add(3);\n primeNumbers.add(5);\n System.out.println(\"LinkedHashSet1: \" + primeNumbers);\n\n LinkedHashSet<Integer> oddNumbers = new LinkedHashSet<>();\n oddNumbers.add(1);\n oddNumbers.add(3);\n oddNumbers.add(5);\n System.out.println(\"LinkedHashSet2: \" + oddNumbers);\n\n \/\/ Difference between LinkedHashSet1 and LinkedHashSet2\n primeNumbers.removeAll(oddNumbers);\n System.out.println(\"Difference : \" + primeNumbers);\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet1: [2, 3, 5]\nLinkedHashSet2: [1, 3, 5]\nDifference: [2]\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nSubset<\/h3>\n\n\n\n
To check if a set is a subset of another set or not, we can use the containsAll()<\/code> method. For example,<\/p>\n\n\n\nimport java.util.LinkedHashSet;\n\nclass Main {\n public static void main(String[] args) {\n LinkedHashSet<Integer> numbers = new LinkedHashSet<>();\n numbers.add(1);\n numbers.add(2);\n numbers.add(3);\n numbers.add(4);\n System.out.println(\"LinkedHashSet1: \" + numbers);\n\n LinkedHashSet<Integer> primeNumbers = new LinkedHashSet<>();\n primeNumbers.add(2);\n primeNumbers.add(3);\n System.out.println(\"LinkedHashSet2: \" + primeNumbers);\n\n \/\/ Check if primeNumbers is a subset of numbers\n boolean result = numbers.containsAll(primeNumbers);\n System.out.println(\"Is LinkedHashSet2 is subset of LinkedHashSet1? \" + result);\n }\n}\n<\/code><\/pre>\n\n\n\nOutput<\/strong><\/p>\n\n\n\nLinkedHashSet1: [1, 2, 3, 4]\nLinkedHashSet2: [2, 3]\nIs LinkedHashSet2 is a subset of LinkedHashSet1? true\n<\/samp><\/code><\/pre>\n\n\n\n
\n\n\n\nOther Methods Of LinkedHashSet<\/h2>\n\n\n\nMethod<\/th> Description<\/th><\/tr> clone()<\/code><\/td>Creates a copy of the LinkedHashSet<\/code><\/td><\/tr>contains()<\/code><\/td>Searches the LinkedHashSet<\/code> for the specified element and returns a boolean result<\/td><\/tr>isEmpty()<\/code><\/td>Checks if the LinkedHashSet<\/code> is empty<\/td><\/tr>size()<\/code><\/td>Returns the size of the LinkedHashSet<\/code><\/td><\/tr>clear()<\/code><\/td>Removes all the elements from the LinkedHashSet<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n