Question

How can I filter an array in Java?

I have an array of objects, for example cars:

Class:

public class Car{
    public int doors;
    public Car(int d){
        this.doors = d;
    }
}

Use:

Car [] cars = new Cars[4];
cars[0] = new Car(3);
cars[1] = new Car(2);
cars[2] = new Car(4);
cars[3] = new Car(6);

Now I want to filter the array of cars, keeping only 4 doors and more:

for(int i = 0; i<cars.length; i++){
    if(cars[i].doors > 4)
         //add cars[i] to a new array
    }
}

How should I do this?

Before I did it with a Vector:

Vector subset = new Vector();
for(int i = 0; i<cars.length; i++){
    if(cars[i].doors > 4)
         //add cars[i] to a new array
        subset.addElement(cars[i]);
    }
}

And then I would make a new array with the size of the Vector. Then I would loop over the vector again and fill the new array. I know this is a very large procedure for something simple.

I’m using J2ME.

Answer 1

EDIT: saw that ArrayList is not in J2ME, but based on documentation, it does have a Vector. If that Vector class is different than J2SE Vector (as this documentation indicates), then perhaps the following code would work:

Vector carList = new Vector();
for(int i = 0; i<cars.length; i++){
    if(cars[i].doors > 4)
         carList.addElement(cars[i]);
    }
}
Car[] carArray = new Car[carList.size()];
carList.copyInto(carArray);