You should override hashCode() and equals() method. you can generate these from IDE.

 @Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof MyData)) return false;

    MyData myData = (MyData) o;

    if (id != myData.id) return false;
    if (!desc.equals(myData.desc)) return false;
    if (!name.equals(myData.name)) return false;

    return true;
}

@Override
public int hashCode() {
    int result = id;
    result = 31 * result + name.hashCode();
    result = 31 * result + desc.hashCode();
    return result;
}

Now you can compare the objects. That's it.

If you're looking to compare objects for equality, serializing them and then comparing is pointless when you can simply override the class' equals method and compare them by their fields (there will undoubtedly be cases where certain fields of the class should not be taken into account, and your method of serialization may not offer that).

Adding "equal" method to each class takes weeks.

I'm sure this isn't the case. Modern IDEs are able to generate these methods for you, and libraries (such as Guava) offer methods that can compare objects by their fields in a single line of code.

No, this is probably not a good idea. What makes objects "equal" depends on the object. Comparing every field for equality may not be the correct test.

Further, the ordering of fields in JSON is not guaranteed, and I am not sure if the order of fields in the binary serialization format are guaranteed either. The serializer deciding in some cases to emit the fields in a different order could result in false negatives.

Here is a simple java object

public class MyObject {

private String firstname;
private String lastname;
private String email;

public String getFirstname() {
    return firstname;
}
public void setFirstname(String firstname) {
    this.firstname = firstname;
}
public String getLastname() {
    return lastname;
}
public void setLastname(String lastname) {
    this.lastname = lastname;
}
public String getEmail() {
    return email;
}
public void setEmail(String email) {
    this.email = email;
}

@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result
            + ((firstname == null) ? 0 : firstname.hashCode());
    result = prime * result
            + ((lastname == null) ? 0 : lastname.hashCode());
    return result;
}
@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    MyObject other = (MyObject) obj;
    if (firstname == null) {
        if (other.firstname != null)
            return false;
    } else if (!firstname.equals(other.firstname))
        return false;
    if (lastname == null) {
        if (other.lastname != null)
            return false;
    } else if (!lastname.equals(other.lastname))
        return false;
    return true;
}
}

(hashcode and equals auto generated by eclipse)

If you look at equals() method, you will see that 2 objects are compared on the fields firstname and lastname, and only those 2. This means that if you insert objects of this type in a list, you will be able to use contains(Object o) and if an object contains the same firstname and lastname, you'll find it.

well, when u serialize it, the state of the object is being saved to a file, not the memory location. When you deserialize it, a new object with the same state is being created internally and a reference to it is being passed to you.

As you have not overridden the equals() method, it is checking only if the memory address is the same.

Override the .equals() method and check whether the states are same yourself.

You can use reflection to do it starting with YourClaas.class.getDeclaredFields(). Then you have to filter the returned fields, retrieve the values from the objects and do the comparison.

From javadocs

When an object is serialized, information that identifies its class is recorded in
the serialized stream. However, the class's definition ("class file") itself is
not recorded. It is the responsibility of the system that is deserializing the
object to determine how to locate and load the necessary class files.

I think that you can follow this tricky way :

1. Place a Conditional Breakpoint when you need to compare the two objects
2. Inside the condition put code to serialize the two Objects (for example with a toJSON function)
3. Compare the output of the serialization(JSON) with the text compare tool