Im trying to loop over an array of objects to return the indexes where there is a match

Question

I am trying to write a class that contains a method that returns a list of indexes of the objects based on a search of one the objects properties.

I have an array Car which has 5 objects with three different properties Color, Make, Model.

public class Car {
    String color;
    String make;
    String model;

public Car(String color, String make, String model){
        this.color = color;
        this.make = make;
        this.model = model;
}

 Car[] myCars =new Car[5];

        myCars[0]=new Car("red", "lexus", "rc350");           
        myCars[1]=new Car("white", "honda", "accord");
        myCars[2]=new Car("red", "honda", "accord");
        myCars[3]=new Car("black", "ford", "mustang");
        myCars[4]=new Car("gray", "lincoln", "navigator");

Now I am trying to loop through this array so that I can search for a given property such as color being red and I would like the indexes 0 and 2 to be added to a new list.

Something like this is what im trying and thinking to do In hopes that it would return an ArrayList or array of ‘0’ and ‘2’:

public class SearchObject{
    List <Integer> getObject (String propertyName, String propertyValue)

searchobject. getObject(“color”,“red”);

I am new to Java and programming in general and would really appreciate any help. Thanks in advance.

if the data doesn't change often, could also pre-populate hashtables (one for each property/facet of the object) to make the search faster — George Birbilis
– George Birbilis, Commented Apr 5, 2018 at 20:19

Hamid Ghasemi · Accepted Answer · 2018-04-05 20:12:37Z

search over objects by strings is a little odd in Java. you can create a sample Entity and fill the variables you want to search. something like the below code:

public class Car {
    String color;
    String make;
    String model;

    public Car(){

    }

    public Car(String color, String make, String model) {
        this.color = color;
        this.make = make;
        this.model = model;
    }

    public boolean equals(Car car){
        if(car.color!= null && !car.color.equals(this.color) )
            return false;
        else if(car.make!= null && !car.make.equals(this.make) )
            return false;
        else if(car.model!= null && !car.model.equals(this.model) )
            return false;

        return true;
    }

    public static void main(String[] args) {

        Car[] myCars = new Car[5];

        myCars[0] = new Car("red", "lexus", "rc350");
        myCars[1] = new Car("white", "honda", "accord");
        myCars[2] = new Car("red", "honda", "accord");
        myCars[3] = new Car("black", "ford", "mustang");
        myCars[4] = new Car("gray", "lincoln", "navigator");

        Car sampleCar = new Car();
        sampleCar.color = "red";

        List<Car> filteredCars = Arrays.stream(myCars).filter(i -> i.equals(sampleCar)).collect(Collectors.toList());
    }
}

Chris Phillips · Accepted Answer · 2018-04-05 20:19:58Z

0

One approach would be to add boolean methods to your Car Class. For example:

public boolean isColor(String aColor){
    boolean ret = false;
    if(this.color.compareTo(aColor) == 0){
        ret = true;
    }
    return ret;
}

nest a switch statement, inside of a for() -loop, and save whichever index of your for-loop evaluates to true. the switch statement should use the first part of your query to determine which method: isColor() isMake() isModel() to call.

answered Apr 5, 2018 at 20:19

Chris Phillips

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