i created setter in sailor class and i want to change email in main class but why my setter wont change the email when its called?

i have tried to change the setter content and implement things to crew class toString method but i cant get it to work, any ideas?

import java.util.ArrayList;

class Sailor {
   private String name;
   private String email;

   public Sailor(String name, String email) {
      this.email = email;
      this.name = name;
   }

   public String getName() {
      return this.name;
   }
   
   public String getEmail() {
      return this.email;
   }

   public void setEmail(String email) {
      this.email = email;
   }
}
    
class Crew {
   ArrayList<Sailor> sailorList = new ArrayList<>();

   public Crew() {}

   public void addCrewMember(Sailor sailor) {
      sailorList.add(new Sailor(sailor.getName(), sailor.getEmail()));
   }

   public String toString() {
      String content = "";

      for (int i = 0; i < sailorList.size(); i  ) {
         content  = sailorList.get(i).getName()   " (";
         content  = sailorList.get(i).getEmail()   ") \n";
      }
      return content;
   }
}
    
class ObjectsCrewProgram {

   public static void main(String[] args) {
      Sailor firstSailor = new Sailor("Frank", "[email protected]");
      Sailor secondSailor = new Sailor("Susan", "[email protected]");
      Sailor thirdSailor = new Sailor("John", "[email protected]");
      Sailor fourthSailor = new Sailor("Ann", "[email protected]");       
      Crew firstCrew = new Crew();
      Crew secondCrew = new Crew();
      firstCrew.addCrewMember(firstSailor);
      firstCrew.addCrewMember(secondSailor);
      firstCrew.addCrewMember(fourthSailor);
      secondCrew.addCrewMember(thirdSailor);
      secondCrew.addCrewMember(secondSailor);
      System.out.println("=== First crew ===\n"   firstCrew); 
      System.out.println("=== Second crew ===\n"   secondCrew);
      secondSailor.setEmail("[email protected]");
      System.out.println("===Second crew ===\n"   secondCrew);
   }
}

CodePudding user response：

why my setter wont change the email when its called?

It does. You're just never observing that change because your program never outputs that value.

You're outputting your crew values:

System.out.println("===Second crew ===\n"   secondCrew);

This uses your .toString() method to generate that output. But what does a "crew" object contain? It doesn't contain the "sailor" objects you provided to it. It contains copies of them:

public void addCrewMember(Sailor sailor) {
    sailorList.add(new Sailor(sailor.getName(), sailor.getEmail()));
}

So your order of operations is:

1. Create a Sailor object.
2. Create a Crew object.
3. Add a copy of the Sailor to the Crew.
4. Modify the original Sailor.
5. Print the Crew.

Instead of creating a copy, just add the Sailor itself to the Crew:

public void addCrewMember(Sailor sailor) {
    sailorList.add(sailor);
}

Then any changes you make to those Sailor objects will be visible in that Crew.

CodePudding user response：

You are creating new sailors with this call:

public void addCrewMember(Sailor sailor) {
    sailorList.add(new Sailor(sailor.getName(), sailor.getEmail()));
}

So you are copying the data and not adding the original sailor. So changing the original sailor has no effect.