Lazy initialization of object passed as argument

Question

Let's say I have a method that takes a very long time to create an object,

public class Foo implements Serializable {
    public static Foo create(...){ 
        /* (takes a long time) */ 
    }
}

I also have a helper class that serializes and deserializes objects,

public class Pickle {
    public static void dump(Serializable obj, String filename) {
        /* ... */
    }
    public static Object load(String filename) {
        /* ... */
    }
}

I want a function that first attempts to load the serialized object specified by filename, but if that fails, creates the object default. It might look something like this:

public Object conditionalCreate(String filename, Object default)
{
    Object obj = null;
    try{
        obj = Pickle.load(filename);
    }
    catch(Exception e){
        obj = default;
    }
    return obj;
}

The way the conditionalCreate function is written now, default will always be created -- I only want to create the default object if it's necessary.

In another language, the conditionalCreate function might look like:

public Object conditionalCreate(String filename, Function defaultConstructor){
    Object obj = null;
    try{
        obj = Pickle.load(filename);
    }
    catch(Exception e){
        obj = defaultConstructor();  /* Note the difference here */
    }
    return obj;
}

Additionally, I'd like a way to pass arguments to this default constructor if construction of the object is necessary (if deserializing failed).

Is something like this possible in Java 7?

I think I'm pretty clear in my question about what my problem is. I'm looking for a way to do something. That something is explained in the question. Am I misunderstanding your comment? — jedwards, Jun 27 '13 at 14:19
Make [java.lang.reflect.Constructor](https://docs.oracle.com/javase/7/docs/api/java/lang/reflect/Constructor.html) the type of the second parameter in method `conditionalCreate`. Or maybe [MethodHandle](https://docs.oracle.com/javase/7/docs/api/java/lang/invoke/MethodHandle.html) is appropriate? Or maybe even a [dynamic proxy](https://docs.oracle.com/javase/7/docs/technotes/guides/reflection/proxy.html) — Abra, Jan 10 '21 at 11:54

darijan · Answer 1 · 2013-06-27T14:36:40.940

0

Not sure if this is what you mean because it seems fairly simple, but:

public <C> C conditionalCreate(String filename, Class<C> defaultType){
    try{
        //try to return loaded element
        return (C) Pickle.load(filename);
    }
    //if it fails log the error
    catch(Exception e){
        Logger.log("Exception happened", e);
    }
    return defaultType.newInstance();
}

edited Jun 27 '13 at 14:36

answered Jun 27 '13 at 14:19

darijan

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The problem with this approach is that I'd have to hard-code `Foo` into the method, I'm looking for a way to pass `Foo` and any necessary initialization arguments *to* this function. So that the function can be used more generally. – jedwards Jun 27 '13 at 14:27

Lazy initialization of object passed as argument

1 Answers1