Grouping products or items based on common categories

The objective is to group the items together based on common categories.

For e.g.1, if there are two items(7000090069,7000090070) associated with three categories (264433,264431,264432) as below :

7000090069 --> 264431

7000090069 --> 264433

7000090070 --> 264433

7000090070 --> 264432

then the output will be 7000090069,7000090070_264433,264431,264432

e.g.2, if there are two items(7000090069,7000090070) associated with three categories

(264431,264432) as below :

7000090069 --> 264431

7000090070 --> 264432

then the output will be 7000090069_264431 and 7000090070_264432 in a list.

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Test {

 /**
  * This class contains items and categories. 
  * The objective is to group the items together based on common categories.
  * For e.g.1, if there are two items(7000090069,7000090070) associated with three categories (264433,264431,264432) as below :
  *   7000090069 --> 264431
  *   7000090069 --> 264433
  *   7000090070 --> 264433
  *   7000090070 --> 264432
  *   then the output will be 7000090069,7000090070_264433,264431,264432
  *   
  *   e.g.2, if there are two items(7000090069,7000090070) associated with three categories (264431,264432) as below :
  *   7000090069 --> 264431
  *   7000090070 --> 264432
  *   then the output will be 7000090069_264431 and 7000090070_264432 in a list.
  */
 static class A {
  long item;
  long category;

  public A(long q, long f) {
   super();
   this.item = q;
   this.category = f;
  }

  public long getItem() {
   return item;
  }

  public void setItem(long q) {
   this.item = q;
  }

  public long getCategory() {
   return category;
  }

  public void setCategory(long f) {
   this.category = f;
  }
 }

 public static void main(String[] args) {
  A[] arr = new A[9];

  arr[0] = new A(7000089688L, 264431);
  arr[1] = new A(7000089707L, 264432);
  arr[2] = new A(7000090069L, 264433);
  arr[3] = new A(7000090047L, 264431);
  arr[4] = new A(7000090051L, 264432);
  arr[5] = new A(7000084083L, 264432);
  arr[6] = new A(7000089688L, 264432);
  arr[7] = new A(7000090070L, 264433);
  arr[8] = new A(7000090070L, 264431);

  List<String> list = new ArrayList<String>();
  int length = 0;

  for (int i = 0; i < arr.length; i++) {
   length = list.size();
   A a = arr[i];
   if (list.isEmpty()) {
    list.add(String.valueOf(a.getItem()) + "_"
      + String.valueOf(a.getCategory()));
    continue;
   }
   boolean added = false;
   for (int j = 0; j < length; j++) {
    String str = list.get(j);
    String[] strArr = str.split("_");
    if (!strArr[0].contains(String.valueOf(a.getItem()))
      && strArr[1].contains(String.valueOf(a.getCategory()))) {
     list.set(j, strArr[0] + "," + String.valueOf(a.getItem())
       + "_" + strArr[1]);
     added = true;
    } else if (strArr[0].contains(String.valueOf(a.getItem()))
      && !strArr[1].contains(String.valueOf(a.getCategory()))) {
     boolean isRemoved = false;
     for (int k = 0; k < length; k++) {
      String str1 = list.get(k);
      String[] strings = str1.split("_");
      if (strings[1]
        .contains(String.valueOf(a.getCategory()))) {
       list.set(
         j,
         strArr[0]
           + ","
           + strings[0]
           + "_"
           + (strArr[1].contains(strings[1]) ? strArr[1]
             : strArr[1] + ","
               + strings[1]));
       list.remove(k);
       length = list.size();
       isRemoved = true;
      }
     }
     if (!isRemoved) {
      list.set(
        j,
        strArr[0] + "_" + strArr[1] + ","
          + String.valueOf(a.getCategory()));
     }
     added = true;
    } else if (strArr[0].contains(String.valueOf(a.getItem()))
      && strArr[1].contains(String.valueOf(a.getCategory()))) {
     added = true;
    }
   }
   if (!added) {
    list.add(String.valueOf(a.getItem()) + "_"
      + String.valueOf(a.getCategory()));
   }
  }

  for (Iterator iterator = list.iterator(); iterator.hasNext();) {
   String string = (String) iterator.next();
   System.out.println(string);
  }
 }
}