Compare Object ArrayList with String ArrayList

Question

I have an String ArraList that fill out from DB. And an Object ArrayList that each object contains some String . Now i want to compare the String ArrayList with one of the Strings of each object in the Object ArrayList . If it equals the Object from Object ArrayList must be remove. Here is my Method Code :

        public ArrayList checkMatches(ArrayList<IceCream> iceCreams, ArrayList<String> blackListPartCodes) { // output is filtered Object ArrayList and two Input,
//one is the Object ArrayList and other is String ArrayList
        int i, j;
        for(i = 0; i<iceCreams.size(); i++) { // Object ArrayList
            IceCream iceCream = iceCreams.get(i);
            for(j = 0; j<blackListPartCodes.size(); j++) { //String ArrayList
                if ((iceCream.getPartCode().matches(blackListPartCodes.get(j)) || iceCream.getPartCode().equals(blackListPartCodes.get(j)))) {
                    iceCreams.remove(iceCream);
                }
            }
        }
            return iceCreams;
        }

Ok,When i use this method, it removes some objects from my Object and decrease the lenght of ArrayList, but does not work correctly. Im i doing something wrong?

I used this code in my app to see if method work fine or not :

            Toast.makeText(getApplicationContext(), "Before : " + iceCreams.size(), Toast.LENGTH_LONG).show(); //324

    checkMatches(iceCreams, blackListPartCodes);
    Toast.makeText(getApplicationContext(), "After : " + iceCreams.size(), Toast.LENGTH_LONG).show(); //200

The first lenght of iceCreams is 324 and when method interact the lenght is 200. I read String ArrayList(blackListPartCodes) from DB, that when i use select Count(myField) from MyTable it says it has 215 rows. that means if it works correctly shoud be 324-215 that is 109. From the other side i display one of the Strings of each object in ListView . Via this :

        for(int i = 0; i<iceCreams.size(); i++) { // the filtered iceCreams after calling `checkMatches`method.
        typeArray.add(iceCreams.get(i).getPartName()); // String ArrayList
        typeAdapter.getItemViewType(R.id.listView); //Adapter of the Array
        iceCreamTypeList.setAdapter(typeAdapter); //Adapter set to ListView
    } 

But in view the fields that are in blackListPartCodes still exist.

Answer 1

I tried to simplyfy your method. It now iterates throw your arrays and places the matches in a new array list. Which is not touching or changing your existing arrays:

public ArrayList checkMatches(ArrayList<IceCream> iceCreams, ArrayList<String> blackListPartCodes) { 
  ArrayList<IceCream> matches = new ArrayList();

  for (IceCream iceCream : iceCreams) {
    for (String blackListPartCode : blackListPartCodes) {
      if (blackListPartCode.equals(iceCream.getPartCode()) 
          || blackListPartCode.matches(iceCream.getPartCode())) {
        matches.add(iceCream);
      }
    }
  }

  return matches;
}

Answer 2

If i == 0 and it finds a match, it removes the item with index 0 in iceCream. All the other items in the list decrease their index by one. So in this example, the item which originally had index 1 will not be checked as its new index is 0 and i == 1.

Instead, keep track of the matching items and remove them after iterating through the list.

Answer 3

Simple solution to compare objects of same class , follow the steps:

1. Open your IceCream.java file.

2. Add following lines of code :
       @Override

public boolean equals(Object o) {
    if (o == null) {
        return false;
    }
    if (getClass() != o.getClass()) {
        return false;
    }
    final IceCream other = (IceCream) o;
    return this.name == other.name;
}

3. Now compare your IceCream class object with another IceCream class object using equals(obj) method. 

Hope! it works. :D

Answer 4

I Finally find out what the problem is. I should identify the iceCream object in inner loop. In this way :

        for(i = 0; i<iceCreams.size(); i++) {
        for(j = 0; j<blackListPartCodes.size(); j++) {
            IceCream iceCream = iceCreams.get(i);

And not this way :

    for(i = 0; i<iceCreams.size(); i++) { // Object ArrayList
        IceCream iceCream = iceCreams.get(i);
        for(j = 0; j<blackListPartCodes.size(); j++) {