I need to check if an object present in list A exists in list B without using nested for loops because if the lists have a large size, it takes too much time.

This is my code :

```
for(Person el : persons)
{
    for(Client in : clients)
    {
        if(el.getIdentifier() == in.getTire().getIdentifier())
        {
            exists=true;
            break;
        }
    }
}

```

How can i achieve the same result without using loops and break?