How to sort Java ArrayList in Descending Order

by Online Tutorials Library July 22, 2022

How to Sort Java ArrayList in Descending Order

By using Collections.reverseOrder(Comparator<T>cmp) method, we can sort the collection in reverse order. The reverseOrder() method does the reversing on the basis of given Comparator. In case of null, it will reverse collection in natural ordering.

Let’s see a simple example to sort the ArrayList in descending order.

SmartPhone.java

 import java.util.Comparator; public class SmartPhone { String brand; String model; intprice; intrating; SmartPhone(String brand,String model,intprice, intrating){ this.brand = brand; this.model = model; this.price = price; this.rating = rating;  } public String getBrand() { returnbrand; } public void setBrand(String brand) { this.brand = brand; } public String getModel() { returnmodel; } public void setModel(String model) { this.model = model; } public int getPrice() { returnprice; } public void setPrice(intprice) { this.price = price; } public int getRating() { returnrating; } public void setRating(intrating) { this.rating = rating; } public String toString() { return”SmartPhone [brand=” + brand + “, model=” + model + “, price=” + price + “, rating=” + rating + “]”; } public int compareTo(SmartPhone sp) { returnthis.price – sp.price;  } } class RatingComparator implements Comparator<SmartPhone> { @Override public int compare(SmartPhone obj1, SmartPhone obj2) { return (obj1.rating<obj2.rating) ? -1 : (obj1.rating>obj2.rating) ? 1 : 0; } } 

ArrayListLearning.java

 public class ArrayListLearning { @SuppressWarnings(“unchecked”) public static void main(String[] args) {  List<SmartPhone> phoneList = new ArrayList<>(); SmartPhone ph1 = new SmartPhone(“Apple”, “6s”, 50000, 10); SmartPhone ph2 = new SmartPhone(“lg”, “pro2”, 40000, 9); SmartPhone ph3 = new SmartPhone(“MI”, “3s”, 10000, 6); SmartPhone ph4 = new SmartPhone(“Letv”, “le2”, 12000, 7);  phoneList.add(ph1); phoneList.add(ph2); phoneList.add(ph3); phoneList.add(ph4); System.out.println(“Actual List”); System.out.println(phoneList); System.out.println(“Sorting the list as comparator”); Collections.sort(phoneList, new RatingComparator());  System.out.println(phoneList); System.out.println(“Reversing the Comparator sorting”); Comparator<SmartPhone> cmp = Collections.reverseOrder(new RatingComparator());  Collections.sort(phoneList, cmp); System.out.println(“Printing the reverse list”); System.out.println(phoneList); }  } 

Output:

Actual List [SmartPhone [brand=Apple, model=6s, price=50000, rating=10],  SmartPhone [brand=lg, model=pro2, price=40000, rating=9],  SmartPhone [brand=MI, model=3s, price=10000, rating=6],  SmartPhone [brand=Letv, model=le2, price=12000, rating=7]] Sorting the list as comparator [SmartPhone [brand=MI, model=3s, price=10000, rating=6],  SmartPhone [brand=Letv, model=le2, price=12000, rating=7],  SmartPhone [brand=lg, model=pro2, price=40000, rating=9],  SmartPhone [brand=Apple, model=6s, price=50000, rating=10]] Reversing the Comparator sorting Printing the reverse list [SmartPhone [brand=Apple, model=6s, price=50000, rating=10],  SmartPhone [brand=lg, model=pro2, price=40000, rating=9],  SmartPhone [brand=Letv, model=le2, price=12000, rating=7],  SmartPhone [brand=MI, model=3s, price=10000, rating=6]]

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