Comparing variables for objects in ArrayList (Java)

Question

I tried searching, but to no avail, I hope you can help me out.

I have an ArrayList containing objects, which all have 4 integer variables. I want my program to throw an Exception , if some of the variables for these objects are identical.. I'll try and write in pseudocode:

for(Object x : ArrayList)
{
    if(x.Variable == someVariables)// all the variables for the objects in the arraylist
    {
        throw exception
    }
}

This is a newbie question, but I hope you can help me out, thanks.

Answer 1

Inside your for loop add them into a set if add method returns false duplicate exist

for(Object x : ArraList)
{
  Set<Integer> set=new HashSet<Integer>();
  for(int i:x.getAllValues()){
      boolean status=set.add(i)
      if(status==false){
        //throw exception
      }
  }
}

write get values method in your object class

OR

Simply create a set from list and check their length

Set<Integer> set= new HashSet<Integer>(list);
if(set.size()!=list.size()){
//contains duplicates
}

Answer 2

Id recommend to implement your value check inside of your class which is your Object 's type. To me it seems to be important that a "thing" like your Object is able to perform a validity check on it's own values. I give you an example:

public class Container {

    // declaration of your four variables

    // other code, maybe getters and setters

    /**
     * Checks if all variables are pairwise inequal
     * @return true if so, false otherwise
     */
    public boolean isValid() {      
        // check vars
    }
}

This way your routine to check all objects of your list is very easy:

for (Container x : arrayList) {
    if (!x.isValid()) {
        throw new RuntimeException("A bad thing just happend!");
    }
}