java - How to put a limit on the amount of objects in an ArrayList -

i'm doing revision o.o.p. exam coming next week , i'm stuck on question. question give example of bi-directional association between dog , flea. far i've got dog fleas. part i'm stuck on is, "modify dog class dog object can hold 5 flea objects max (print "your dog has many fleas!" if there's more 5 fleas). here's code far:

dog.java

import java.util.arraylist;  public class dog {      private string name;     private int age;     private string address;      arraylist<flea> fleas = new arraylist<flea>(); {         if(fleas.size() > 5) {              system.out.println("this dog has many fleas!");         }     }      public string getname() {         return name;     }      public void setname(string name) {         this.name = name;     }      public int getage() {         return age;     }      public void setage(int age) {         this.age = age;     }      public string getaddress() {         return address;     }      public void setaddress(string address) {         this.address = address;     }      public void hostflea(flea flea) {         fleas.add(flea);     }      public arraylist<flea> getdogflea() {          return fleas;     }      public string tostring() {         return name + " dog (aged " + age + ") has fleas. \nthey are: " + fleas + ".";     }     } 

flea.java

public class flea {      private string name;     private int age;       public flea (string name, int age) {         this.name = name;         this.age = age;     }      public string getname() {         return name;     }      public void setname(string name) {         this.name = name;     }      public int getage() {         return age;     }      public void setage(int age) {         this.age = age;     }      public string tostring() {         return name + " (aged " + age + ")";     }  } 

test.java

public class test {      public static void main(string[] args) {          dog dog = new dog();             dog.setname("freddy");             dog.setaddress("cork");             dog.setage(5);          flea flea1 = new flea("john", 1);         dog.hostflea(flea1);          flea flea2 = new flea("patrick", 3);                 dog.hostflea(flea2);          flea flea3 = new flea("alan", 7);         dog.hostflea(flea3);          flea flea4 = new flea("steven", 2);         dog.hostflea(flea4);          flea flea5 = new flea("charles", 5);         dog.hostflea(flea5);          flea flea6 = new flea("derek", 1);         dog.hostflea(flea6);          flea flea7 = new flea("kevin", 8);         dog.hostflea(flea7);          system.out.println(dog);      }  } 

console:

freddy dog (aged 5) has fleas. are: [john (aged 1), patrick (aged 3), alan (aged 7), steven (aged 2), charles (aged 5), derek (aged 1), kevin (aged 8)].

add checking condition here:

public void hostflea(flea flea) {     if(fleas.size() >= 5) {         system.out.println("this dog has many fleas!");     } else {         fleas.add(flea);     } } 

not @ definition of list variable (as did), because added an instance initialization block.