A basic example of the Strategy pattern.

TeresaStrategyPattern.java

import java.util.Random;
public interface MeleeAttackBehavior {
    public int meleeAttack();
}
public interface RangedAttackBehavior {
    public int rangedAttack();
}
public class Melee3d6 implements MeleeAttackBehavior {
    public int meleeAttack() {
        Random rnd = new Random();
        return rnd.nextInt(6)+rnd.nextInt(6)+rnd.nextInt(6)+3;
    }
}
public class Melee2d4 implements MeleeAttackBehavior {
    public int meleeAttack() {
        Random rnd = new Random();
        return rnd.nextInt(4)+rnd.nextInt(4)+2;
    }
}
public class Ranged2d4 implements RangedAttackBehavior {
    public int rangedAttack() {
        Random rnd = new Random();
        return rnd.nextInt(4)+rnd.nextInt(4)+2;
    }
}
public class NoRangedAttack implements RangedAttackBehavior {
    public int rangedAttack() {
        return 0;
    }
}
public abstract class Character {
    private int health;
    private MeleeAttackBehavior melee;
    private RangedAttackBehavior ranged;
    public Character(int health, MeleeAttackBehavior melee, RangedAttackBehavior ranged) {
        this.health = health;
        this.melee = melee;
        this.ranged = ranged;
    }
    public int wound(int dmg) {
        this.health = (this.health > dmg) ? this.health-dmg : 0;
        return this.health == 0;
    }
    public int meleeAttack() {
        return this.melee.meleeAttack();
    }
    public int rangedAttack() {
        return this.ranged.rangedAttack();
    }
}
public class Knight extends Character {
    public Knight() {
        super(18, new Melee3d4(), new NoRangedAttack());
    }
}
public class Rogue extends Character {
    public Rogue() {
        super(12, new Melee3d6(), new Ranged2d4());
    }
}
public class GiantRat extends Character {
    public GiantRat() {
        super(10, new Melee2d4(), new NoRangedAttack());
    }
}