Subset/indices of array of objects based on object attributes

Question

Let's say I have an array of objects like dummies[] below. I want to find the index of array objects where their attribute a == 5 or a > 3 etc.

class Dummy{
  int a;
  int b;
  public Dummy(int a,int b){
    this.a=a;
    this.b=b;
  }
}
public class CollectionTest {
  public static void main(String[] args) {
       //Create a list of objects
      Dummy[] dummies=new Dummy[10];
      for(int i=0;i<10;i++){
          dummies[i]=new Dummy(i,i*i);
      }

      //Get the index of array where a==5
      //??????????????????????????????? -- WHAT'S BEST to go in here? 
  }
}

Is there any way other than iterating over the array objects and check for the conditions? Does using ArrayList or other type of Collection help here?

You will need to iterate through the array and add matching value dummies to a new array. — Menno
– Menno, Commented Apr 16, 2013 at 21:05
A simple iteration will let you find a given item, but a better question is why do you want the index? Or are you actually looking for the object that has a==5? — Nathaniel Ford
– Nathaniel Ford, Commented Apr 16, 2013 at 21:14
I need the indices because I am keeping a table of associations. There is a second array whic has objects which encompass only "a" variable. I need to match them with the objects in this array and do some calculations. a==5 is just an example. I have a range of values. — AKG
– AKG, Commented Apr 17, 2013 at 13:05

Miguel Prz · Accepted Answer · 2013-04-16 21:06:53Z

1

// Example looking for a==5
// index will be -1 if not found
int index = -1;
for( int i=0; i<dummies.length; i++ ) {
   if( dummies[i].a == 5 ) {
      index = i;
      break;
   }
}

answered Apr 16, 2013 at 21:06

Miguel Prz

13.8k32 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Subset/indices of array of objects based on object attributes

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related