How to Sort an Array of Objects by a Property in Java?

Question

How do I sort an array of objects by the name property in Java?

public String toString() {
    return (name + "\n" + id + "\n" + author + "\n" + publisher + "\n");
}

Answer

Sorting an array of objects in Java can be accomplished by utilizing the built-in sorting methods provided by the Java Collections Framework. In order to sort the objects based on a property, such as 'name', you will need to create a comparator or utilize the Comparable interface if this is a common operation for your object class.

import java.util.Arrays;
import java.util.Comparator;

class Book {
    String name;
    int id;
    String author;
    String publisher;

    public Book(String name, int id, String author, String publisher) {
        this.name = name;
        this.id = id;
        this.author = author;
        this.publisher = publisher;
    }

    @Override
    public String toString() {
        return (name + "\n" + id + "\n" + author + "\n" + publisher + "\n");
    }
}

public class SortArrayOfObjects {
    public static void main(String[] args) {
        Book[] books = {
                new Book("Java Programming", 1, "Author A", "Publisher A"),
                new Book("Python Programming", 2, "Author B", "Publisher B"),
                new Book("C++ Programming", 3, "Author C", "Publisher C")
        };

        Arrays.sort(books, new Comparator<Book>() {
            @Override
            public int compare(Book b1, Book b2) {
                return b1.name.compareTo(b2.name);
            }
        });

        for (Book book : books) {
            System.out.print(book);
        }
    }
}

Causes

Not using the correct method to extract the property for sorting.
Not implementing the Comparable interface in the object class.

Solutions

Use Arrays.sort with a custom Comparator that extracts the property for sorting.
Implement Comparable in the object class for natural sorting.

Common Mistakes

Mistake: Not defining a proper comparison method for sorting.

Solution: Implement the compareTo method or provide a Comparator to define sorting logic.

Mistake: Ignoring case sensitivity during string comparison.

Solution: Use compareToIgnoreCase method for case-insensitive sorting.

Helpers

sort array of objects Java
sort by property Java
Java arrays
Comparator in Java
Comparable interface Java