Merging two objects in Java

Question

I have two objects of same type.

Class A {
  String a;
  List b;
  int c;
}

A obj1 = new A();
A obj2 = new A();

obj1 => {a = \"hello\"; b = null; c = 10         


        

Answer 1

There is a dynamic solution to merge any two objects which require Reflection and Recursion.

public <T> T merge(T local, T remote, ArrayList<String> listOfClass)
        throws IllegalAccessException, InstantiationException {
    Class<?> clazz = local.getClass();
    Object merged = clazz.newInstance();
    for (Field field : clazz.getDeclaredFields()) {
        field.setAccessible(true);
        Object localValue = field.get(local);
        Object remoteValue = field.get(remote);
        if (localValue != null) {
            if (listOfClass.contains(localValue.getClass().getSimpleName())) {
                field.set(merged, this.merge(localValue, remoteValue, listOfClass));
            } else {
                field.set(merged, (remoteValue != null) ? remoteValue : localValue);
            }
        } else if (remoteValue != null) {
            field.set(merged, remoteValue);
        }
    }
    return (T) merged;
}

Variable Description:

• local: The object on to which the other will be merged
• remote: The object which will be merged to the local object
• listOfClass: The ArrayList of custom classes in the given object

The function returns a merged object which is good to go.

Kudos! :)

Answer 2

Just accommodating boolean sync. and case sensitive(camel notation)

public boolean merge(Object obj){

    if(this.equals(obj)){
        return false;
    }

    if(!obj.getClass().isAssignableFrom(this.getClass())){
        return false;
    }

    Method[] methods = obj.getClass().getMethods();

    for(Method fromMethod: methods){
        if(fromMethod.getDeclaringClass().equals(obj.getClass())
                && (fromMethod.getName().matches("^get[A-Z].*$")||fromMethod.getName().matches("^is[A-Z].*$"))){

            String fromName = fromMethod.getName();
            String toName ;
            if(fromName.matches("^get[A-Z].*")){
                toName = fromName.replace("get", "set");
            }else{
                toName = fromName.replace("is", "set");
            }

            try {
                Method toMetod = obj.getClass().getMethod(toName, fromMethod.getReturnType());
                Object value = fromMethod.invoke(this, (Object[])null);
                if(value != null){
                    toMetod.invoke(obj, value);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } 
        }
    }

    return true;
}