Java sort string array using Array.sort() like python's sorted with key=lambda x:

I'm occasionally learning Java. As a person from python background, I'd like to know whether there exists something like sorted(iterable, key=function) of python in java.

For exmaple, in python I can sort a list ordered by an element's specific character, such as

>>> a_list = ['bob', 'kate', 'jaguar', 'mazda', 'honda', 'civic', 'grasshopper']
>>> s=sorted(a_list) # sort all elements in ascending order first
>>> s
['bob', 'civic', 'grasshopper', 'honda', 'jaguar', 'kate', 'mazda'] 
>>> sorted(s, key=lambda x: x[1]) # sort by the second character of each element
['jaguar', 'kate', 'mazda', 'civic', 'bob', 'honda', 'grasshopper'] 

So a_list is sorted by ascending order first, and then by each element's 1 indexed(second) character.

My question is, if I want to sort elements by specific character in ascending order in Java, how can I achieve that?

Below is the Java code that I wrote:

import java.util.Arrays;

public class sort_list {
  public static void main(String[] args)
  {
    String [] a_list = {"bob", "kate", "jaguar", "mazda", "honda", "civic", "grasshopper"};
    Arrays.sort(a_list);
    System.out.println(Arrays.toString(a_list));}
  }
}

and the result is like this:

[bob, civic, grasshopper, honda, jaguar, kate, mazda] 

Here I only achieved sorting the array in ascending order. I want the java array as the same as the python list result.

Java is new to me, so any suggestion would be highly appreciated.

Thank you in advance.

Use a custom comparator to compare two strings.

Arrays.sort(a_list, Comparator.comparing(s -> s.charAt(1)));

This compares two strings by the string's second character.

This will result in

[kate, jaguar, mazda, civic, bob, honda, grasshopper]

I see that jaguar and kate are switched in your output. I'm not sure how Python orders two String that are equal. The Arrays.sort does stable sort.

> This sort is guaranteed to be <i>stable</i>: equal elements will
not be reordered as a result of the sort.

You can supply a lambda function to Arrays.sort. For your example, you could use:

Arrays.sort(a_list, (String a, String b) -> a.charAt(1) - b.charAt(1));

Assuming you have first sorted the array alphabetically (using Arrays.sort(a_list)) this will give you your desired result of:

['jaguar', 'kate', 'mazda', 'civic', 'bob', 'honda', 'grasshopper'] 

You can use Comparator.comparing to sort the list

Arrays.sort(a_list, Comparator.comparing(e -> e.charAt(1)));

And if you want to sort and collect in the new list using Java Stream API

String [] listSorted =  Arrays.stream(a_list)
                              .sorted(Comparator.comparing(s -> s.charAt(1)))
                              .toArray(String[]::new);