Checking an ArrayList of Objects for a string

Question

I am having trouble with looking through my ArrayList of FacebookPerson object for a string (name). This is my first project working with ArrayLists, and as such I have, at best, only a basic idea of what I'm doing. What I'm not understanding is why fbUsers.contains(name) does not seem to do anything, and how I can correctly search for a string name.

---testFacebook_ArrayList.java

package Facebook;

import java.util.*;

public class testFacebook_ArrayList {
    public static Scanner Input = new Scanner(System.in);

    public static void main(String[] args){
        String name, mood;
        boolean exit = false;
        ArrayList<FacebookPerson> fbUsers = new ArrayList<FacebookPerson>();

        while(!exit){
        System.out.print("Enter the name of a facebook user to be created (enter #### to end creation & move to user selection): ");
        name = Input.next();
        Input.nextLine();

            if(name.equals("####")){
            exit = true;
            }
            else if(fbUsers.contains(new FacebookPerson(name))){
                System.out.println("Error, name already exists. Try again.");
                continue;
            }
            else{
                fbUsers.add(new FacebookPerson(name));
            }
        }
        exit = false;
        while (!exit){
            System.out.print("Enter a user's name to modify their mood (#### to terminate the program): ");
            name = Input.nextLine();

            if (name.equals("####")){
                System.out.println("Program terminated.");
                System.exit(1);
            }
            else if (fbUsers.contains(new FacebookPerson(name))){
                System.out.print("Enter a mood for " + name + ": ");
                mood = Input.nextLine();
                for (int i = 0; i < fbUsers.size(); i++){
                    if(fbUsers.get(i).equals(new FacebookPerson(name))){
                        fbUsers.get(i).setMood(mood);
                    }
                }
            }
            else{
                System.out.println("Unrecognized name. Try again.");
                continue;
            }
        }
    }
}

---FacebookPerson.java

  // This is the FacebookPerson_Graphics class
  // Written by Dr. Xiaolin Hu
  // 03/05/2015
  package Facebook;

  public class FacebookPerson{

  private String myName;
  protected String myMood;
  protected Facebook myfacebook;

  public FacebookPerson(String name){
      myName = name;
      myfacebook = new Facebook(myName);
      //System.out.println("FacebookPerson's constructor");
  }

  public FacebookPerson(){

  }

  public String getName(){
      return myName;
  }

  public void setMood(String newMood){
     myMood = newMood;
     myfacebook.setContent(myMood);
  }

  public String getMood(){
      return myMood;
  }

}

---Facebook.java

// This is the Facebook class
// Wrriten by Dr. Xiaolin Hu
// 03/05/2015
package Facebook;

import java.awt.*;

public class Facebook{

   private String name;
   private String content;
   DrawingPanel panel;
   private Graphics g;

   public Facebook(String nm){
       content = "undefined";
       name = nm;

       // Create the drawing panel
       panel = new DrawingPanel(200, 150);
       g = panel.getGraphics();

       // display name
       g.drawString(name+"'s mood is undefined.", 20, 75);
   }

   public void setContent(String newContent){
    content = newContent;
        if(content.equals("happy")){
            g.setColor(Color.red);
            g.fillRect(0, 0, 200, 150);
            g.setColor(Color.black);
            // display mood
            g.drawString(name+"'s mood is:"+ "happy", 20, 75);
        }
        else{
            g.setColor(Color.white);
            g.fillRect(0, 0, 200, 150);
            g.setColor(Color.black);
            g.drawString(name+"'s mood is:"+ content, 20, 75);
        }
   }

   public String getContent(){
    return content;
   }
}

I'm assuming because you are doing fbUsers.contains(name) as name is a String but fbUsers contains FacebookPerson you most likely would need to make your own method for this. Or do what @Fungucide said above — 3kings
– 3kings, Commented Nov 13, 2015 at 5:23
Unfortunately Fungucide's method did not work. It seems to ignore it completely still. — Calderious
– Calderious, Commented Nov 13, 2015 at 5:25

WIR3D · Accepted Answer · 2015-11-13 05:53:15Z

2

You could do a for loop for every user and call getName();

for (FacebookPerson fbp : fbUsers ){
     if (fbp.getName().equals(name)){
          System.out.println("Error, name already exists. Try again.");
          continue;
     }
}

edited Nov 13, 2015 at 5:53

answered Nov 13, 2015 at 5:29

WIR3D

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6 Comments

Calderious Over a year ago

For some reason, this still does not work for me. Even with this comparison, it still seems to be ignored.

WIR3D Over a year ago

Please just post the whole code so I can help you debug

Calderious Over a year ago

Done. Though, you should know that there are some other issues with my code as well not relating to this quesiton.

thegauravmahawar Over a year ago

@Fungucide you do not compare String like that.

thegauravmahawar Over a year ago

@Fungucide please see the if condition in your alternative solution

|

Will F. · Accepted Answer · 2015-11-13 06:44:03Z

1

You could use a 2d array list to store the information and link it to the name. That would fix your problem

answered Nov 13, 2015 at 6:44

Will F.

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Comments

Matthew Cachia · Accepted Answer · 2015-11-13 06:40:00Z

0

Calderious,

You need to override and implement FacebookPerson's equals(...) method in order for contains to work. If you look at the List's contains(...) javadoc, it specifically mentions:

... returns true if and only if this collection contains at least one element e such that (o==null ? e==null : o.equals(e)).

add the following in your class

public class FacebookPerson {
  ...

  @Override
  public boolean equals(Object obj) {
    // your equals logic goes here
  }

  ...
}

or even better, IDEs can now create this based on your declared attributes. In Eclipse, you just need to right click on the code > Source > Generate hashCode() and equals().

I hope that helps.

answered Nov 13, 2015 at 6:40

Matthew Cachia

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