Making use of Arrays in java

Question

Consider the following code,

import java.util.ArrayList;
public class UselessCode {
public static void main(String args[]){

    ArrayList<Integer> x = new ArrayList<Integer>();
        x.add(81);
        x.add(53);
        x.add(27);

            for(int i=0; i < Data.size(); ++i)
            {
                System.out.println(x.get(i));
            }
        }
    }

The output of the code above prints out the three numbers I have added to the array as expected.

Is there a way to modify the code so it adds a persons name to each number?

For example, the output would the be ("Mark", 81), ("Scot", 53) and so on.

You probably need a list of Person objects, each Person having a name field and a number field. Instead of ArrayList<Integer>, you would thus have an ArrayList<Person>. — JB Nizet
– JB Nizet, Commented Feb 15, 2014 at 12:10

Jeroen Vannevel · Accepted Answer · 2014-02-15 12:09:50Z

First of all: you're looking at ArrayLists, not arrays.

And yes, that's possible. This is when you create your own class that holds these two fields.

class Person {
    private int age; // Or make it a date object
    private String name;

    // Constructor
    // Getters
}

After which you simply have a list of Person objects:

List<Person> people = new ArrayList<>();
people.add(new Person("John", 21));

You should read through this tutorial for a good overview.

Sidenote: you can't have spaces in your class name. I also suggest you follow the Java Naming Conventions by starting the classname with an uppercase character (and by making it descriptive).

Another possibility is using a HashMap<String, Integer> but I feel like a custom class is more warranted here.

There are quite a bit of links in this post, I suggest you read through them all since these are elementary concepts that all your programs will depend on.

Warlord · Accepted Answer · 2014-02-15 12:16:01Z

2

ArrayList<Integer> is set to store only Integer values, if you need to add another items, I would suggest that you consider creating your own class, such as Person, that would contain both number and name.

class Person {

public int number;
public String name;

}

and then you can make an ArrayList<Person>, that contains the whole object and access its individual fields like this:

System.out.println("Id of the person %d", list.get(i).number);
System.out.println("Name of the person %s", list.get(i).name);

edited Feb 15, 2014 at 12:16

answered Feb 15, 2014 at 12:10

Warlord

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Comments

Saddam Abu Ghaida · Accepted Answer · 2014-02-15 12:15:16Z

0

you need to use map instead of array , or create a class for name and number and to the array but now you add objects instead of integeres

edited Feb 15, 2014 at 12:15

answered Feb 15, 2014 at 12:10

Saddam Abu Ghaida

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