join two lists in java without null

Question

i have two lists they are of type car .

car class has 4 strings variable :

    color;
 model;

//for second

color;
model;

now i want to join these two lists with out any null cuz first list has :

color="red";
model=null;

second list ;

color=null
model="2010"

so I want them like:

color="red";
model="2010"

without null

Where are these lists and why do you say 4 string variables? That looks like 2 per Car. — Martin Dinov
– Martin Dinov, Commented Mar 15, 2014 at 19:59
So it seems like there are just two Car objects with 2 strings in there. Where are the lists? — Martin Dinov
– Martin Dinov, Commented Mar 15, 2014 at 20:02
Why not construct the code so you don't have those nulls in the first place? — wakjah
– wakjah, Commented Mar 15, 2014 at 20:06
cuz i read it from database and don't know where is the null — user3376574
– user3376574, Commented Mar 15, 2014 at 20:11

clcto · Accepted Answer · 2014-03-15 20:04:14Z

1

If I understand you correctly, then you want to create a List<Car> that gets the color from one list and the model from the other. To do this, just create new Cars and add them to a new List:

List<Car> newlist = new ArrayList<Car>();
for( int i = 0; i < list1.size() && i < list2.size(); ++i )
    newlist.Add( new Car( list1.get(i).getColor(), list2.get(i).getModel() ) );

However if you do not know which list contains null for each car, you would have to do some checks:

for( int i = 0; i < list1.size() && i < list2.size(); ++i )
{
    String color = list1.get(i).getColor();
    if( color == null )
        color = list2.get(i).getColor();

    String model = list1.get(i).getModel();
    if( model == null )
        model = list2.get(i).getModel();

    newlist.Add( new Car( color, model ) );
}

Note: I assumed Car has a common interface, ie:

class Car
{
    public String getModel(){ return model; }
    public String getColor(){ return color; }
    public Car( String c, String m )
    {
        color = c;
        model = m;
    }
}

answered Mar 15, 2014 at 20:04

clcto

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3 Comments

user3376574 Over a year ago

note that size of list1 not equal list2 so it will get out of index

clcto Over a year ago

It won't get out of index, it just won't look at all of them.

user3376574 Over a year ago

if size of list1 is 5 and size of list2 10 then the code will out in i=4

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