How to extract an array of only one attribute from a List

Question

I always need to extract an array of any kind of object from a list, let me explain with code:

This is my list:

List<myObj> myList = new ArrayList<myObj>();

My object has 2 objects, 'foo' and 'bar':

public class myObj{

    private Object foo;
    private Object bar;

    public myObj(Object foo, Object bar) {
        super();
        this.foo = foo;
        this.bar = bar;
    }
}

So, i populate myList:

myList.add(new myObj(foo1, bar1));
myList.add(new myObj(foo2, bar2));
myList.add(new myObj(foo3, bar3));

Is there any way to extract into a array just the foo's Objects without programming or creating a method for that? Example:

Return: Array [foo1, foo2, foo3]

I don't think there is. You'll have to iterate over myList and extract the objects you want — alexgbelov
– alexgbelov, Commented Mar 8, 2017 at 19:42
Just a side note: I don't see a reason to call super() when your class doesn't actually extend any other class. — domsson
– domsson, Commented Mar 8, 2017 at 19:44
myList.stream().map(myObj::getFoo).collect(Collectors.toList()). Don't use arrays. Use lists. — JB Nizet
– JB Nizet, Commented Mar 8, 2017 at 19:45
Are you trying to serialize a json? There are ways to ignore attributes depending on the library that you are using. — Luis Lavieri
– Luis Lavieri, Commented Mar 8, 2017 at 19:46
@domdom Yes, i know, but Java's good pratice tells to do it, just for pratice btw — KpsLok
– KpsLok, Commented Mar 8, 2017 at 19:46

KpsLok · Accepted Answer · 2017-03-08 23:40:37Z

2

As indicated by @JB Nizet in comments:

myList.stream().map(myObj::getFoo).collect(Collectors.toList‌()). Don't use arrays. Use lists

It solved my problem! Thank you!

answered Mar 8, 2017 at 23:40

KpsLok

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