How to Sort LinkedHashSet of Custom Class Objects using TreeSet in Java?
The LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all elements present in java.util package. When the iteration order is needed to be maintained, this class is used.
Input : Student = {{"c",2},{"b",1},{"a",3}}
Output:
Sort by name = {{"a",3},{"b",1},{"c",2}}
Sort by rollNo = {{"b",1},{"c",2},{"a",3}}
Approach 1:
In the example instead of using custom classes, the wrapper classes of java like Integer, Double, Float, etc to sort LinkedHashSet using TreeSet is used. For doing this convert LinkedHashSet element into TreeSet and can do this in three different ways:-
- By using the constructor of TreeSet.
- By using for loop and add() method.
- By using addAll() method.
Implementation:
Java
// Java Program to sort LinkedHashSet of custom // class objects using TreeSet import java.util.Collections; import java.util.LinkedHashSet; import java.util.TreeSet; public class GFG { public static void main(String[] args) { // creating a LinkedHashSet LinkedHashSet<Double> lset0 = new LinkedHashSet<>(); // adding elements to LinkedHashSet lset0.add(1.009); lset0.add(1.10); lset0.add(1.01); lset0.add(1.019); // creating a TreeSet // and adding LinkedHashSet element to TreeSet // using the constructor of the TreeSet TreeSet<Double> tset0 = new TreeSet<>(lset0); // Displaying the output System.out.println("Sorted Set(ascending): " + tset0); // creating a LinkedHashSet LinkedHashSet<Integer> lset1 = new LinkedHashSet<>(); // adding elements to LinkedHashSet lset1.add(10); lset1.add(7); lset1.add(2); lset1.add(20); // creating TreeSet TreeSet<Integer> tset1 = new TreeSet<>(); // adding LinkedHashSet element to TreeSet // using for loop and add() method for (Integer i : lset1) tset1.add(i); // Displaying the output System.out.println("Sorted Set(ascending): " + tset1); // creating LinkedHashSet LinkedHashSet<Character> lset2 = new LinkedHashSet<>(); // adding elements to the LinkedHashSet lset2.add('s'); lset2.add('h'); lset2.add('i'); lset2.add('n'); // creating a TreeSet TreeSet<Character> tset2 = new TreeSet<>(); // adding LinkedHashSet element to TreeSet // element using addAll() method tset2.addAll(lset2); System.out.println("Sorted Set(ascending): " + tset2); // creating a LinkedHashSet LinkedHashSet<String> lset3 = new LinkedHashSet<>(); // adding elements to the // LinkedHashSet lset3.add("Sandra"); lset3.add("Shishya"); lset3.add("Sarthak"); lset3.add("Sarah"); lset3.add("Sagar"); lset3.add("Sashi"); lset3.add("Sonika"); // creating a TreeSet but this time it will // sort it in descending order // so for sorting in descending order // we will use Collections.reverseOrder() in // the constructor of TreeSet TreeSet<String> tset3 = new TreeSet<>(Collections.reverseOrder()); // adding elements of LinkedHashSet to treeSet // using addAll() method tset3.addAll(lset3); // Displaying output System.out.println("Sorted Set(descending): " + tset3); } } |
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Output
Sorted Set(ascending): [1.009, 1.01, 1.019, 1.1] Sorted Set(ascending): [2, 7, 10, 20] Sorted Set(ascending): [h, i, n, s] Sorted Set(descending): [Sonika, Shishya, Sashi, Sarthak, Sarah, Sandra, Sagar]
Approach 2:
In this, the Comparator interface is used. Comparator interface is used to order the objects of user-defined classes. A comparator object is capable of comparing two objects of two different classes.
Implementation:
Java
Java Program to sort LinkedHashSet of custom // class objects using TreeSet import java.util.Comparator; import java.util.LinkedHashSet; import java.util.TreeSet; class friendsMarks { // class field String name; String nickName; int marks; // parameterised constructor public friendsMarks(String name, String nickName, int marks) { this.name = name; this.nickName = nickName; this.marks = marks; } // getter for name public String getName() { return name; } // setter for name public void setName(String name) { this.name = name; } // getter for marks public int getMarks() { return marks; } // setter for marks public void setMarks(int marks) { this.marks = marks; } // getter for nickname public String getNickName() { return nickName; } // setter for nickname public void setNickName(String nickName) { this.nickName = nickName; } //@Override toString method public String toString() { return "friendsMarks{" + "name='" + name + '\'' + ", nickName='" + nickName + '\'' + ", marks=" + marks + '}'; } } // for comparing names class nameCompare implements Comparator<friendsMarks> { @Override public int compare(friendsMarks friend1, friendsMarks friend2) { return friend1.getName().compareTo( friend2.getName()); } } // for comparing nick name class nickNameCompare implements Comparator<friendsMarks> { @Override public int compare(friendsMarks obj1, friendsMarks obj2) { return obj1.getNickName().compareTo( obj2.getNickName()); } } // for comparing marks class marksCompare implements Comparator<friendsMarks> { @Override public int compare(friendsMarks f1, friendsMarks f2) { if (f1.getMarks() > f2.getMarks()) { return 1; } else { return -1; } } } public class Main { public static void main(String[] args) { // Creating LinkedHashSet LinkedHashSet<friendsMarks> linkedHashSet = new LinkedHashSet<>(); // adding elements to LinkedHashSet linkedHashSet.add( new friendsMarks("Raushan", "Chamgader", 99)); linkedHashSet.add( new friendsMarks("Yashdeep", "Dopa", 95)); linkedHashSet.add( new friendsMarks("Rupesh", "Gian", 92)); linkedHashSet.add( new friendsMarks("Shishya", "Gorilla", 47)); linkedHashSet.add( new friendsMarks("Sarthak", "Nagin", 78)); linkedHashSet.add( new friendsMarks("Sonika", "Chipkali", 67)); linkedHashSet.add( new friendsMarks("Himanshu", "Lalten", 57)); // Creating TreeSet // and we have to pass Comparator object // of marksCompare class // in the TreeSet constructor // so that we can sort according to the marks TreeSet<friendsMarks> treeSet0 = new TreeSet<>(new marksCompare()); // storing elements of LinkedHashSet // into TreeSet by using method addAll() treeSet0.addAll(linkedHashSet); System.out.println("Sorting on the basis of marks"); // Displaying using loop for (friendsMarks tree : treeSet0) System.out.println(tree); // Creating TreeSet // and we have to pass Comparator object // of nameCompare class // in the TreeSet constructor // so that we can sort according to the name TreeSet<friendsMarks> treeSet1 = new TreeSet<>(new nameCompare()); // storing elements of LinkedHashSet // into TreeSet by using method addAll() treeSet1.addAll(linkedHashSet); // Displaying using loop System.out.println( "\n\nSorting on the basis of name"); for (friendsMarks tree : treeSet1) System.out.println(tree); // Creating TreeSet // and we have to pass Comparator object // of nickNameCompare class // in the TreeSet constructor // so that we can sort according to the nickname TreeSet<friendsMarks> treeSet2 = new TreeSet<>(new nickNameCompare()); // storing elements of LinkedHashSet // into TreeSet by using method addAll() treeSet2.addAll(linkedHashSet); // Displaying using loop System.out.println( "\n\nSorting on the basis of nick-name"); for (friendsMarks tree : treeSet2) System.out.println(tree); } } |
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Output
Sorting on the basis of marks
friendsMarks{name='Shishya', nickName='Gorilla', marks=47}
friendsMarks{name='Himanshu', nickName='Lalten', marks=57}
friendsMarks{name='Sonika', nickName='Chipkali', marks=67}
friendsMarks{name='Sarthak', nickName='Nagin', marks=78}
friendsMarks{name='Rupesh', nickName='Gian', marks=92}
friendsMarks{name='Yashdeep', nickName='Dopa', marks=95}
friendsMarks{name='Raushan', nickName='Chamgader', marks=99}
Sorting on the basis of name
friendsMarks{name='Himanshu', nickName='Lalten', marks=57}
friendsMarks{name='Raushan', nickName='Chamgader', marks=99}
friendsMarks{name='Rupesh', nickName='Gian', marks=92}
friendsMarks{name='Sarthak', nickName='Nagin', marks=78}
friendsMarks{name='Shishya', nickName='Gorilla', marks=47}
friendsMarks{name='Sonika', nickName='Chipkali', marks=67}
friendsMarks{name='Yashdeep', nickName='Dopa', marks=95}
Sorting on the basis of nick-name
friendsMarks{name='Raushan', nickName='Chamgader', marks=99}
friendsMarks{name='Sonika', nickName='Chipkali', marks=67}
friendsMarks{name='Yashdeep', nickName='Dopa', marks=95}
friendsMarks{name='Rupesh', nickName='Gian', marks=92}
friendsMarks{name='Shishya', nickName='Gorilla', marks=47}
friendsMarks{name='Himanshu', nickName='Lalten', marks=57}
friendsMarks{name='Sarthak', nickName='Nagin', marks=78}
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