Java ArrayList sort() Method

Java ArrayList Java ArrayList

The sort() method sorts the elements in the dynamic array according to the specified order.

The syntax of the sort() method is:

arraylist.sort(Comparator c)

Note:arraylist is an object of the ArrayList class.

Parameter Description:

  • comparator - the ordering method

Return Value

The sort() method does not return any value; it simply changes the order of the elements in the dynamic array list.

Example

Sort in natural order; the following is the order of the letters:

Example

import java.util.ArrayList;
import java.util.Comparator;

class Main {
    public static void main(String[] args){

        // Create a dynamic array
        ArrayList<String> sites = new ArrayList<>();
       
        sites.add("Example");
        sites.add("Google");
        sites.add("Wiki");
        sites.add("Taobao");
        System.out.println("Website list: " + sites);

        System.out.println("Unsorted: " + sites);

        // Sort the elements in ascending order
        sites.sort(Comparator.naturalOrder());
        System.out.println("Sorted: " + sites);
    }
}

Executing the above program produces the following output:

网站列表: [Example, Google, Wiki, Taobao]
不排序: [Example, Google, Wiki, Taobao]
排序后: [Google, Example, Taobao, Wiki]

In the above example, we used the sort() method to sort a dynamic array named sites.

Note this line:

sites.sort(Comparator.naturalOrder());

Here, the naturalOrder() method of the Java Comparator interface specifies that the elements are sorted in natural order (ascending).

The Comparator interface also provides a method for sorting elements in descending order:

Example

import java.util.ArrayList;
import java.util.Comparator;

class Main {
    public static void main(String[] args){

        // Create a dynamic array
        ArrayList<String> sites = new ArrayList<>();
       
        sites.add("Example");
        sites.add("Google");
        sites.add("Wiki");
        sites.add("Taobao");
        System.out.println("Website list: " + sites);

        System.out.println("Unsorted: " + sites);

        // Descending order
        sites.sort(Comparator.reverseOrder());
        System.out.println("Descending sort: " + sites);
    }
}

Executing the above program produces the following output:

网站列表: [Example, Google, Wiki, Taobao]
不排序: [Example, Google, Wiki, Taobao]
降序排序: [Wiki, Taobao, Example, Google]

In the above example, the reverseOrder() method of the Comparator interface specifies that the elements are sorted in reverse order (descending).

Java ArrayList Java ArrayList

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