Java: Just sorting strings after the space?

Question

I'm making a program that sorts names based on last name, but user enters a full name such as "John Smith" and I can't get it to sort by the name after the space.

It seems to only want to sort by the first name entered and ignore the last, but I want to sort by last name

        System.out.println("Welcome to name sorter program");

    //Set max names to 10
    String [] names = new String[10];
    String temp;
    for (int i = 0; i < names.length; i++)
    {
        System.out.println("Enter person " +(i + 1));
        //Name entered is assigned to each array slot
        names[i] = userInput.nextLine();
    }
        for (int i = 0; i < names.length; i++)
    {
        for (int j = i + 1; j < names.length; j++ )
        {
            if (names[i].compareTo(names[j]) > 0)
            {
                temp = names[i];
                names[i] = names[j];
                names[j] = temp;
            }
        }
    }
    System.out.println("Sorted Names Are...");
    for (int i = 0; i < names.length - 1; i++)
    {
        System.out.println(names[i]);
    }
        System.out.println(names[names.length - 1]);
}

Okay. Why can't you? Is there a question you meant to ask here? — Stack Exchange Broke The Law
– Stack Exchange Broke The Law, Commented Sep 27, 2016 at 3:22
Because my code seems to only sort by the first name entered — user6861432
– user6861432, Commented Sep 27, 2016 at 3:23
Yes, that is what your code does. Why can't you change it so it does what you want it to do? — Stack Exchange Broke The Law
– Stack Exchange Broke The Law, Commented Sep 27, 2016 at 3:23
Split the string, and only compare the part after the space. — Miki P
– Miki P, Commented Sep 27, 2016 at 3:29

Marcel · Accepted Answer · 2016-09-27 04:49:32Z

My answer is almost the same of @BahramdunAdil:

public class Main {

    public static void main(String[] args) {

        final int MAX = 10;

        Scanner userInput = new Scanner(System.in);

        List<Person> names = new ArrayList<Person>();

        System.out.println("Welcome to name sorter program!\n");

        for (int i = 0; i < MAX; i++) {
            System.out.println("Enter person " + (i + 1) + ":");
            names.add(new Person(userInput.nextLine()));
        }

        userInput.close();

        Collections.sort(names);

        System.out.println("\nSorted Names Are...");

        for (Person name : names)
            System.out.println(name);
    }

}

i.e, you can turn your code simpler creating a Person Class that implements Comparable:

public class Person implements Comparable<Person> {
    private String firstName;
    private String lastName;

    public Person(String name) {
        this.firstName = name.split(" ")[0];
        this.lastName = name.split(" ")[1];
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    @Override
    public int compareTo(Person o) {
        return lastName.compareTo(o.getLastName());
    }

    @Override
    public String toString() {
        return firstName + " " + lastName;
    }
}

Input:

Welcome to name sorter program!

Enter person 1:
Bill Gates
Enter person 2:
Amancio Ortega
Enter person 3:
Warren Buffett
Enter person 4:
Carlos Slim Helu
Enter person 5:
Jeff Bezos
Enter person 6:
Mark Zuckerberg
Enter person 7:
Larry Ellison
Enter person 8:
Michael Bloomberg
Enter person 9:
Charles Koch
Enter person 10:
David Koch

Output:

Sorted Names Are...
Jeff Bezos
Michael Bloomberg
Warren Buffett
Larry Ellison
Bill Gates
Charles Koch
David Koch
Amancio Ortega
Carlos Slim
Mark Zuckerberg

Bahramdun Adil · Accepted Answer · 2016-09-27 06:42:16Z

You can do it with the Collections, here is an example: Create a Person class and implement the Comparable interface and then do comparison in the compareTo() method...

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    List<Person> persons = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        System.out.println("Enter person " +(i + 1));
        String line = in.nextLine();
        // split the name with apace
        String[] array = line.split(" ");
        // crate a new Person
        Person person = new Person(array[0], array[1]);
        // add to the Person list
        persons.add(person);
    }

    // now sort it
    Collections.sort(persons);

    // after sort
    System.out.println("persons = " + persons);
}

static class Person implements Comparable<Person> {
    private String firstName;
    private String lastName;

    public Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    @Override
    public int compareTo(Person o) {
        return lastName.compareTo(o.lastName);
    }

    @Override
    public String toString() {
        return "Person{" + "firstName='" + firstName + '\'' + ", lastName='" + lastName + '\'' + '}';
    }
}

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