In this article, we will discuss how to sort contents of LinkedHashSet
Key points about LinkedList:
- LinkedHashSet maintains insertion-order
- It uses doubly-linked list and hash table to store element/objects
Different ways to sort LinkedHashSet :
- Convert LinkedHashSet to TreeSet for natural-ordering
- Convert LinkedHashSet to TreeSet for reverse-ordering by providing Comparator based customized-sorting logic
- Using ArrayList and Collections class’ utility method sort();
Let us move forward to discuss different ways to sort LinkedHashSet contents
1. Convert LinkedHashSet to TreeSet for natural-ordering
- Create new LinkedHashSet object
- Store/add contents to LinkedHashSet
- Create new TreeSet object,
- Pass LinkedHashSet contents as argument to TreeSet’ inter-conversion constructor
Syntax:
// convert LinkedHashSet to TreeSet
TreeSet<String> tSet = new TreeSet<String>(lhsCompanies);
SortingLinkedHashSetUsingTreeSet.java
package in.bench.resources.collection;
import java.util.LinkedHashSet;
import java.util.TreeSet;
public class SortingLinkedHashSetUsingTreeSet {
public static void main(String[] args) {
// creating LinkedHashSet object of type String
LinkedHashSet<String> lhsCompanies =
new LinkedHashSet<String>();
// adding elements to LinkedHashSet object
lhsCompanies.add("LinkedIn");
lhsCompanies.add("Amazon");
lhsCompanies.add("Google");
lhsCompanies.add("Apple");
lhsCompanies.add("Facebook");
lhsCompanies.add("Oracle");
lhsCompanies.add("Microsoft");
// Iterating using enhanced for-loop
System.out.println("Insertion Order:"
+ " Iterating LinkedHashSet\n");
for(String company : lhsCompanies) {
System.out.println(company);
}
// convert LinkedHashSet to TreeSet
TreeSet<String> tSet = new TreeSet<String>(lhsCompanies);
// Iterating using enhanced for-loop
System.out.println("\n\nAscending sorting-order:"
+ " Iterating TreeSet\n");
for(String company : tSet) {
System.out.println(company);
}
}
}
Output:
Insertion Order: Iterating LinkedHashSet
LinkedIn
Amazon
Google
Apple
Facebook
Oracle
Microsoft
Ascending sorting-order: Iterating TreeSet
Amazon
Apple
Facebook
Google
LinkedIn
Microsoft
Oracle
2. Convert LinkedHashSet to TreeSet for reverse-ordering
- Create new LinkedHashSet object
- Store/add contents to LinkedHashSet
- Create new TreeSet object and provide reverse-order sorting-logic using Comparator
- Add LinkedHashSet contents to TreeSet using addAll(); method
Syntax:
// create new TreeSet object and provide reverse-sorting logic
TreeSet<String> tSet = new TreeSet<String>(
new Comparator<String>() {
@Override
public int compare(String str1, String str2) {
return str2.compareTo(str1);
}
});
ReverseSortingLinkedHashSetUsingTreeSet.java
package in.bench.resources.collection;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.TreeSet;
public class ReverseSortingLinkedHashSetUsingTreeSet {
public static void main(String[] args) {
// creating LinkedHashSet object of type String
LinkedHashSet<String> lhsCompanies =
new LinkedHashSet<String>();
// adding elements to LinkedHashSet object
lhsCompanies.add("LinkedIn");
lhsCompanies.add("Amazon");
lhsCompanies.add("Google");
lhsCompanies.add("Apple");
lhsCompanies.add("Facebook");
lhsCompanies.add("Oracle");
lhsCompanies.add("Microsoft");
// Iterating using enhanced for-loop
System.out.println("Insertion Order:"
+ " Iterating LinkedHashSet\n");
for(String company : lhsCompanies) {
System.out.println(company);
}
// create new TreeSet object and provide reverse-sorting logic
TreeSet<String> tSet = new TreeSet<String>(
new Comparator<String>() {
@Override
public int compare(String str1, String str2) {
return str2.compareTo(str1);
}
});
// add LinkedHashSet to TreeSet for reverse-sorting elements
tSet.addAll(lhsCompanies);
// Iterating using enhanced for-loop
System.out.println("\n\nDescending sorting-order:"
+ " Iterating TreeSet\n");
for(String company : tSet) {
System.out.println(company);
}
}
}
Output:
Insertion Order: Iterating LinkedHashSet
LinkedIn
Amazon
Google
Apple
Facebook
Oracle
Microsoft
Descending sorting-order: Iterating TreeSet
Oracle
Microsoft
LinkedIn
Google
Facebook
Apple
Amazon
3. Using ArrayList and Collections’ class utility method sort()
- Create new LinkedHashSet object
- Store/add contents to LinkedHashSet
- Convert LinkedHashSet to ArrayList using inter-conversion constructor
- Invoke sort(); method on ArrayList contents using Collections‘ class
- Invoke clear(); method on original LinkedHashSet, if we want to convert back ArrayList to LinkedHashSet
- Finally, convert ArrayList to LinkedHashSet by adding ArrayList contents to LinkedHashSet, as LinkedHashSet maintains insertion-order, if we want to retain original LinkedHashSet
- Note : we can sort in reverse-order using Comparator and providing reverse-order sorting logic
Syntax:
// convert LinkedHashSet to ArrayList
List<String> lst = new ArrayList<String>(lhsCompanies);
// sort using Collections class
Collections.sort(lst);
// clear or empty LinkedHashSet
lhsCompanies.clear();
// convert sorted ArrayList to LinkedHashSet, afetr clear();
lhsCompanies.addAll(lst);
SortingLinkedHashSetUsingArrayList.java
package in.bench.resources.collection;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
public class SortingLinkedHashSetUsingArrayList {
public static void main(String[] args) {
// creating LinkedHashSet object of type String
LinkedHashSet<String> lhsCompanies =
new LinkedHashSet<String>();
// adding elements to LinkedHashSet object
lhsCompanies.add("LinkedIn");
lhsCompanies.add("Amazon");
lhsCompanies.add("Google");
lhsCompanies.add("Apple");
lhsCompanies.add("Facebook");
lhsCompanies.add("Oracle");
lhsCompanies.add("Microsoft");
// Iterating using enhanced for-loop
System.out.println("Insertion Order:"
+ " Iterating LinkedHashSet\n");
for(String company : lhsCompanies) {
System.out.println(company);
}
// convert LinkedHashSet to ArrayList
List<String> lst = new ArrayList<String>(lhsCompanies);
// sort using Collections class
Collections.sort(lst);
// clear or empty LinkedHashSet
lhsCompanies.clear();
// convert sorted ArrayList to LinkedHashSet, afetr clear();
lhsCompanies.addAll(lst);
// Iterating using enhanced for-loop
System.out.println("\n\nAscending sorting-order:"
+ " Iterating LinkedHashSet\n");
for(String company : lhsCompanies) {
System.out.println(company);
}
}
}
Output:
Insertion Order: Iterating LinkedHashSet
LinkedIn
Amazon
Google
Apple
Facebook
Oracle
Microsoft
Ascending sorting-order: Iterating LinkedHashSet
Amazon
Apple
Facebook
Google
LinkedIn
Microsoft
Oracle
References:
- https://docs.oracle.com/javase/tutorial/collections/intro/
- https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html
- https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Set.html
- https://docs.oracle.com/javase/7/docs/api/java/util/class-use/HashSet.html
- https://docs.oracle.com/javase/7/docs/api/java/util/HashSet.html
- https://docs.oracle.com/javase/7/docs/api/java/util/LinkedHashSet.html
- http://docs.oracle.com/javase/7/docs/api/index.html?java/util/class-use/LinkedHashSet.html
Happy Coding !!
Happy Learning !!
