Proper looping construct using Arrays and List

Question

In this simple example, i want to create a String array populated with each person's first and last in my DB. I know i am missing something very obvious as i keep overriding i in the following looping method. A second eye would certainly help.

    /**
 * 
 * @return
 */
public String[] buildFullNameContainer(){

    List<Person> allPeople = Person.findAllPeople();
    String[] peopleContainer = new String[] {""};
    String fullName = "";



        for (int i = 0; i < peopleContainer.length; i++) {
            for (Person person : allPeople) {
                fullName = person.getFirstName() + " " + person.getLastName();  
                peopleContainer[i] = fullName; 

            }
        }
    return peopleContainer;
}

There is only one value when i loop through the String array after calling this method — Warz
– Warz, Commented Jun 14, 2012 at 20:12
@Warz: How would you expect there to ever be more than one element? You're creating an array with one element to start with, and arrays never expand... — Jon Skeet
– Jon Skeet, Commented Jun 14, 2012 at 20:14

Jon Skeet · Accepted Answer · 2012-06-14 20:13:34Z

4

Your array always has a single element - you should create it to be the same length as your list. Additionally, you've got two nested loops for no reason, and I see no point in the fullName variable. Here's the code I'd use:

String[] peopleContainer = new String[allPeople.size()];

for (int i = 0; i < peopleContainer.length; i++) {
    Person person = allPeople.get(i);
    peopleContainer[i] = person.getFirstName() + " " + person.getLastName();
}

answered Jun 14, 2012 at 20:13

Jon Skeet

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Comments

Eng.Fouad · Accepted Answer · 2012-06-14 20:12:47Z

3

Replace

String[] peopleContainer = new String[] {""};

with

String[] peopleContainer = new String[allPeople.size()];

Also, edit your loop as follows:

for(int i = 0; i < peopleContainer.length; i++)
{
    Person person = allPeople.get(i);
    fullName = person.getFirstName() + " " + person.getLastName();  
    peopleContainer[i] = fullName;  
}

answered Jun 14, 2012 at 20:12

Eng.Fouad

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3 Comments

Warz Over a year ago

if i remove the outter for loop, how can i reference 'i' as it does not exist

SimplyPanda Over a year ago

Initialize an int i at the beginning. In the peopleContainer[i] = fullName; line, change the i to a i++.

Warz Over a year ago

Best answer as it gets rid of the unnecessary inner for-loop. will accept in a few

ioseb · Accepted Answer · 2012-06-14 20:13:49Z

0

I believe this needs to be changed from:

String[] peopleContainer = new String[] {""};

To:

String[] peopleContainer = new String[allPeople.size()];

answered Jun 14, 2012 at 20:13

ioseb

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Comments

sharakan · Accepted Answer · 2012-06-14 20:15:54Z

0

You're looping over your result array, instead of your source data collection. You have to size the array correctly first, then loop over the size of either the array or the list. No need for a nested for.

public String[] buildFullNameContainer(){

    List<Person> allPeople = Person.findAllPeople();
    String[] peopleContainer = new String[allPeople.size()];
    for (int i = 0; i < peopleContainer.length; i++) {
        Person person = allPeople.get(i);
        String fullName = person.getFirstName() + " " + person.getLastName();  
        peopleContainer[i] = fullName; 
    }
return peopleContainer;
}

answered Jun 14, 2012 at 20:15

sharakan

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Comments

Akhi · Accepted Answer · 2012-06-14 20:16:46Z

0

Try This.

    List<Person> allPeople = Person.findAllPeople();
    String[] peopleContainer = new String[allPeople.size()];

    for (int i=0;i < allPeople.size();i++;) {
          Person person=allPeople.get(i);
          fullName = person.getFirstName() + " " + person.getLastName();  
          peopleContainer[i] = fullName; 
    }

answered Jun 14, 2012 at 20:16

Akhi

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