Java ArrayList serialization issue

Question

It is first time when I am doing serialization/deseraialization and I have an issue what I cannot understand. So I have an employee class:

public class Employee implements Serializable{

private static final long serialVersionUID = -8987739485808870716L;
public  String firstName; 
public String lastName;
public int phoneNumber;
public ArrayList<Skill> empSkillAry = new ArrayList<Skill>(); //

Skill class:

   public class Skill implements Serializable {

private static final long serialVersionUID = 4862257193587272698L;
public int skillID;
public String skillName;

Schedule class:

    public class Schedule implements Serializable {

private static final long serialVersionUID = 781243452337862636L;
String Name;
int CsID;
public ArrayList<Skill> skillRequiredAry = new ArrayList<Skill>();

To empSkillAry and skillRequiredAry are added skill object. If empSkillAry contains all skillRequiredAry objects, employee can be assigned to the shift. Lets say, employee has skill 1 and schedule also has skill 1. before serialization when comparing both arrays I get a positive result, however after deserialization it is negative. Is there something wrong whith my serialization and deserialization code? Here it is:

private static   void deserializeAry(ArrayList arrayToDesirialize,  String filePath){
    try {
        FileInputStream fileIn = new FileInputStream(filePath);
        ObjectInputStream in = new ObjectInputStream(fileIn);
        arrayToDesirialize = (ArrayList) in.readObject();
        System.out.println(arrayToDesirialize);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

private static void serializeAry(ArrayList arrayToSerialize, String filePath){
    try {
        FileOutputStream fileOut = new FileOutputStream(filePath);
        ObjectOutputStream out = new ObjectOutputStream(fileOut);
        System.out.println(arrayToSerialize.toString());
        out.writeObject(arrayToSerialize);
        fileOut.close();
        out.close();


    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    }

Java Doe · Accepted Answer · 2015-12-19 15:16:02Z

4

Your skill class does not have an ''equals()'' method. When you add a skill to both lists, they both contain the same object, but after deserialization they contain different objects with the same content! If you implement an equals method and compare with that instead of == it should work

answered Dec 19, 2015 at 15:16

Java Doe

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3 Comments

Roberts Rakvics Over a year ago

When I am comparing these two arrays I use containsAll(), as I need to be sure that employee has all required skills. No, I do not have an equals() method in skill class. I will implement it straight away .

Java Doe Over a year ago

The containsAll method uses the equals method to compare, so it should suffice to implement it, as the equals inherited from object compares object equality... Another hint: if you implement equals you should also implement hashCode! But you can use your IDE to implement the two (at least eclipse can do that) to make sure they are consistent

Roberts Rakvics Over a year ago

I implemented an equals() method in a skill class. That solved my problem. Thank you for help

Peter Lawrey · Accepted Answer · 2015-12-19 15:17:29Z

2

I assume you are writing these arrays to different files? This means you will be getting different objects when you deserialize them. i.e. None of the Skill objects in the two arrays will be the same object. They should be .equals assuming you implemented this method.

BTW, In your debugger you should be able to see the object's id number is different even though the contents is the same.

answered Dec 19, 2015 at 15:17

Peter Lawrey

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