Sorting Arrays.asList In Java

Question

import java.util.Arrays;
import java.util.List;

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

        List<String> topNames2017 = Arrays.asList(
            "Amelia", 
            "Olivia", 
            "emily", 
            "Isla", 
            "Ava", 
            "oliver", 
            "Jack",
            "Charlie", 
            "harry", 
            "Jacob"
        );               

        for(int i = 0; i < topNames2017.size(); i++) {
            topNames2017.set(i, capitalize(topNames2017.get(i))); 
        }   

        List<String> sorted = Arrays.asList(
            topNames2017.stream().sorted(
                (s1, s2) -> s1.compareToIgnoreCase(s2)
                ).toArray(String[]::new)
            );

        sorted.forEach(System.out::println);
    }
    private static String capitalize(final String line) {
        return Character.toUpperCase(line.charAt(0)) + line.substring(1);
    }
}

The above code works and sorts it the way I want to.

How can I sort that alphabetically and making sure the first letter is capitalized using method references?

Help is greatly appreciated!

Answer 1

It is not entirely clear whether you really want the case insensitive order, or whether capitalizing the strings and then sorting them (case-sensitively) would be sufficient, but the difference should not be important.

You asked

How can I sort that alphabetically and making sure the first letter is capitalized using method references?

In order to use the reference for the capitalize method, you have to use the YourClassName::capitalize syntax.

An example is shown below:

• It creates a Stream of names from the given list
• The stream of names is mapped to capitalized names, using a method reference to the capitalize method
• The stream of capitalized names is sorted (case-insensitively - you could just omit the String.CASE_INSENSITIVE_ORDER if this didn't matter)
• The resulting stream is collected into a new List<String>

The full code:

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class CapitalizeAndSort {

    public static void main(String[] args) {

        List<String> topNames2017 = Arrays.asList(
            "Amelia", 
            "Olivia", 
            "emily", 
            "Isla", 
            "Ava", 
            "oliver", 
            "Jack",
            "Charlie", 
            "harry", 
            "Jacob"
        );               

        List<String> sorted = topNames2017.stream()
            .map(CapitalizeAndSort::capitalize)
            .sorted(String.CASE_INSENSITIVE_ORDER)
            .collect(Collectors.toList());

        sorted.forEach(System.out::println);
    }

    private static String capitalize(final String line) {
        return Character.toUpperCase(line.charAt(0)) + line.substring(1);
    }
}

Answer 2

You can sort alphabetically writing like below:

Collections.sort(topNames2017, String.CASE_INSENSITIVE_ORDER);

and make first letter capitalized writing like below:

topNames2017 = topNames2017.substring(0, 1).toUpperCase() + topNames2017.substring(1);