How to Sort Java List Objects by Date property with Examples

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How to Sort Java List Objects by Date property with Examples

In the tutorial, We discuss how to Sort Java List Objects by Date property with difference Date types: java.util.Date(using SimpleDateFormat), LocalDate, LocalDateTime. Java provides 2 main approaches for sorting Java List with Comparator:

• Using java.util.Collections.sort(List list, Comparator super Customer> c): sorting the specified list according to the order providing by the specified comparator.
• Using Java 8 Stream API to sort java.util.Collection.stream().sorted(Comparator super T> comparator): returning a stream consisting of the elements of this stream, sorted according to the provided Comparator.

Let's do more details with Java syntax examples (Java 7 and Java 8 Stream + Lamda Expression) by descending and ascending sorting order.

Overview Sorting with Collections.sort()

For sorting a Java List with Objects, we use Collections.sort() API:

public static <T> void sort(List<T> list, Comparator<? super T> c) {
    list.sort(c);
}

• Sorts the specified list according to the order induced by the specified comparator.
• According to Oracle: "This implementation is a stable, adaptive, iterative mergesort that requires far fewer than n lg(n) comparisons when the input array is partially sorted, while offering the performance of a traditional mergesort when the input array is randomly ordered. If the input array is nearly sorted, the implementation requires approximately n comparisons. Temporary storage requirements vary from a small constant for nearly sorted input arrays to n/2 object references for randomly ordered input arrays."

Exception:

• ClassCastException - if the list contains elements that are not mutually comparable using the specified comparator.
• UnsupportedOperationException - if the specified list's list-iterator does not support the set operation.
• IllegalArgumentException - (optional) if the comparator is found to violate the Comparator contract

  Using Collections.sort() - Sorting Java Objects Examples by java.util.Date property

  We create a Java Class Object that has a birthday property with java.util.Date type as below:

import java.text.SimpleDateFormat;
import java.util.Date;

class Customer {
    private int id;
    private String name;
    private Date birthday;
    
    public Customer(int id, String name, Date birthday){
        this.id = id;
        this.name = name;
        this.birthday = birthday;
    }
    
    public int getId() {
        return id;
    }
    
    public Date getBirthday() {
        return this.birthday;
    }
    
    public String toString() {
        return String.format("id = %d, name = %s, birthday = %s", this.id, this.name, this.birthday.toString());
    }
}

• Create a List of Customer as below:

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https://grokonez.com/java/how-to-sort-java-list-objects-by-date-property-with-examples

How to Sort Java List Objects by Date property with Examples