Lambda Expressions - Java 8 Recipes - page 225

Type Description

Static Reference Uses a static method of an object.

Instance Reference Uses an instance method of an object.

Arbitrary Object
Method

Used on an arbitrary object of a particular type, rather than a particular
object.

Constructor Referen-
ce

Used to generate a new object by invoking a constructor with the new
keyword.

In the solution, the static method reference type is demonstrated since com-
pareByGoal() is a static method within a static class. It is possible to invoke a
method of an object instance using an instance reference. Consider the following class,
which contains a non-static method for comparing goals within Player objects.

public class PlayerUtility {

public int compareByGoal(Player a, Player b){
int eval;
if(a.getGoals() > b.getGoals()){
eval = 1;
} else if (a.getGoals() < b.getGoals()){
eval = -1;
} else {
eval = 0;

}
return eval;

}

}

This class can be instantiated, and the new instance can be used to reference the
compareByGoals() method, similarly to the technique that was used in the solu-
tion to this recipe.

Player[] teamArray2 = team.toArray(new
Player[team.size()]);
PlayerUtility utility = new PlayerUtility();
Arrays.sort(teamArray2, utility::compareByGoal);