Sort array after deleting value

Question

how can I sort an Array after deleting one value?

e.g. {1,2,3,4,5} --> {1,2,null,4,5} --> {1,2,4,5,null}.

public boolean removeNumber(int accountNumber) {
    for(int i = 0; i < Account.length; i++) {
        if(Account[i].getAccountNumber() == (accountNumber)) {
            Account[i] = null;
        }

Thats an other issue I havent resolved yet. But number must be int. — , Dec 19 '17 at 20:45
if `Account[i]` you can't compare to an int (and comparing is with == and not =) I'd suggest you *EDIT* and explain better or you'll question will be closed soon ;) Why would you remove an account ? because of what element ? (give Account class) — azro, Dec 19 '17 at 20:46

score 1 · Answer 1 · answered Dec 19 '17 at 20:57

You can follow this way to achieve this :

You need to find the accounts that have the accountNumber you're looking for
you set them to null on the array
You sort the array with a custom Comparator :
- if an element is null it has to go at the end
- if both are not-null you compare their accountNumber

public boolean removeNumber(int accountNumber) {
    for (int i = 0; i < Account.length; i++) {
        if (Account[i].getAccountNumber() == accountNumber) {
            Account[i] = null;
        }
    }
    Arrays.sort(Account, (o, p) -> {
        if (o == null)
            return 1;
        if (p == null)
            return -1;
        return Integer.compare(o.getAccountNumber(), p.getAccountNumber());

    });
    return true;
}

Tips :

follow naming conventions : camelCasefor attriutes ==> Account[] becomes account[]
use .equals() when you are comparing object, for an int == is right

score 1 · Accepted Answer · answered Dec 19 '17 at 22:47

Since your original array is already sorted, and assuming that only one Account can have that particular accountNumber, there is no need to sort the array again. Just locate the element to remove, then shift everything after that element down one position, and null out the newly-freed element.

I've renamed the Account field to accounts to follow Java naming conventions, to make a clearer distinction between the array (accounts) and the class (Account), both for the future developers looking at the code, and for the Java compiler.

public boolean removeNumber(int accountNumber) {
    for (int i = 0; i < accounts.length; i++) {
        if (accounts[i].getAccountNumber() == accountNumber) {
            System.arraycopy(accounts, i + 1, accounts, i, accounts.length - i - 1);
            accounts[accounts.length - 1] = null;
            return true; // Found and removed
        }
    }
    return false; // Not found, so nothing removed
}

Now, if you insist on sorting the array, you can do it like this in Java 8+:

Arrays.sort(accounts, Comparator.nullsLast(Comparator.comparing(Account::getAccountNumber)));

Thanks! Thats what i was looking for :D – Dec 20 '17 at 00:33 — , Dec 20 '17 at 00:33

Sort array after deleting value

2 Answers2