Problem

Hello. Let's looks to "this" method over constructor. >>> pulic Kot () { ....... sould be fulfil for "this"....}

The way that the logical OR (two ||) works in an if statement is that it will compare boolean values to the left and right of it and if one or the other is true, the whole statement is true. When you use it more than once, like on line 18, it evaluates each condition in order and will stop and result in true the very first expression that is true. So you code first checks: 1) "this.wiek > innyKot.wiek", if this is true line 18 will be true and goes to line 20, otherwise it checks 2) "this.waga > innyKot.waga", if true line 18 is true and goes to line 20, otherwise it checks 3) "this.sila > innyKot.sila" if this is true it goes to line 20, otherwise it goes to line23 This would be the same as:

if (this.wiek > innyKot.wiek)
   return true;
else if (this.waga > innyKot.waga)
   return true;
else if (this.sila > innyKot.sila)
   return true;
else return false;

So if you have cats with different stats for wiek, waga, and sila it is possible that some are high and some are low, and the scenario can happen that both cats "win". You will have to figure out how you can use those three stats to get a clear winner and a clear loser. A simple method would be to just add them up, but you can try any algorithm that makes sense to you.