How to add multiple object in ArrayList which declared generic?

Question

How to do that?

Following is tried code.

[Tried code]

package com.company;

import java.util.ArrayList;
import java.util.Date;

public class Main {
    public static void main(String[] args) {
        ArrayList<String, Integer, Date> myArray = new ArrayList<String, Integer, Date>();

        myArray.add("FIRST");
        myArray.add("SECOND");
        myArray.add("THIRD");

        // add multiple object
        myArray.add(new Integer(10));

        // add multiple object
        myArray.add(new Date());

    }
}

What you are going to achieve by this? Seems you are doing something wrong — Abimaran Kugathasan
– Abimaran Kugathasan, Commented Nov 29, 2013 at 6:08
You can't do like that, I mean, you can't make it add only those three object types. — Abimaran Kugathasan
– Abimaran Kugathasan, Commented Nov 29, 2013 at 6:11

Suresh Atta · Accepted Answer · 2013-11-29 06:08:04Z

1

Yes, But not recommended.

ArrayList<Object> myArray = new ArrayList<Object>();

Taking Object as a type , it accept all the types.

ArrayList<Object> myArray = new ArrayList<Object>();
myArray.add("FIRST");   //accepted
myArray.add(new Integer(10));  //accepted
myArray.add(new Date());  //accepted

So while getting also you need to take care of which Object you are getting back.

But, good recommendation is to take that individual list's for each type.

answered Nov 29, 2013 at 6:08

Suresh Atta

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Comments

Rahul · Accepted Answer · 2013-11-29 06:08:17Z

0

The below line wouldn't even compile.

ArrayList<String, Integer, Date> myArray = new ArrayList<String, Integer, Date>();

What you're trying to achieve can be done using

ArrayList<Object> myArray = new ArrayList<>(); // Object type

but it is not at all a recommended option to do it. And while fetching the values back from the ArrayList, you need to handle the different types of objects manually, which is quite troublesome as well.

Therefore, it is always create ArrayList of the specific types you want to use.

ArrayList<String> myString = new ArrayList<>(); // For strings
ArrayList<Date> myDates = new ArrayList<>(); // For Date

answered Nov 29, 2013 at 6:08

Rahul

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3 Comments

S.J. Lim Over a year ago

I can't understand why generic of JAVA doesn't have this feature which can specify each objects.

S.J. Lim Over a year ago

Thank R.J. You make me know it's recommended way.

Rahul Over a year ago

@user868754 - Glad to be of help to you! :)

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