[Java 8] Sorting method in alphabetical order and string length order that can be used in coding tests

background

Recently, I've been declining in the WEB coding test for job change activities. I'm practicing at paiza.io because I think I have to get used to it. If you are too busy to solve it, you will see the source at a later date and mass-produce the nauseating fucking code.

This time, I will summarize the method of sorting after storing in List .

Operating environment

• java 1.8.0_191

• Because we are using a Comparator, please note that it will not work on Java 7 or earlier.

java.util.Comparator;Imagine you are importing.

# Alphabetical order

```java
List<String> list = Arrays.asList("ABC", "DEFGH", "IJKL", "abc", "defgh", "ijkl");

//Alphabetical ascending order (case insensitive)
//Output result: ABC,abc,DEFGH,defgh,IJKL,ijkl
list.sort(String.CASE_INSENSITIVE_ORDER);

//Descending alphabetical order (case insensitive)
//Output result: IJKL,ijkl,DEFGH,defgh,ABC,abc
list.sort(String.CASE_INSENSITIVE_ORDER.reversed());

//Alphabetical ascending order (case sensitive)
//Output result: ABC,DEFGH,IJKL,abc,defgh,ijkl
list.sort(Comparator.naturalOrder());

//Descending alphabetical order (case sensitive)
//Output result: ijkl,defgh,abc,IJKL,DEFGH,ABC
list.sort(Comparator.reverseOrder());

String length order

List<String> list = Arrays.asList("ABC", "DEFGH", "IJKL", "abc", "defgh", "ijkl");

//Ascending order of string length
//Output result: ABC,abc,IJKL,ijkl,DEFGH,defgh
list.sort(Comparator.comparingInt(String::length));

//String length descending
//Output result: DEFGH,defgh,IJKL,ijkl,ABC,abc
list.sort(Comparator.comparingInt(String::length).reversed());

bonus

Character string length → Sort alphabetically

list.sort(Comparator.comparingInt(String::length).thenComparing(Comparator.naturalOrder()));

How to sort Integer.

List<Integer> list = Arrays.asList(1, 3, 2);

//ascending order
Collections.sort(list);

//descending order
Collections.reverse(list);

At the end

It can be realized with Lambda, but I personally feel that Comparator is more readable, so I omitted it. I want to come out quickly without investigating this much.

Coding tests often require this sort of sorting, so it's a good idea to remember! This one is more readable! Please let us know if you have any opinions or mistakes.