Behaviors

Providing native behaviors for many Java types.

Consider the following: Java has an interface called Iterable, which many types of Java collections implement. Now, if we found a way to make it follow the iterable protocol, we could easily iterate over any Java class in TypeScript.

This is where the Behavior API comes in. You define a predicate, and an apply as a behavior. Once that Java class is initialized somewhere, if it meets the predicate, it will be applied.

Keep in mind this is the TypeScript API. There will almost certainly also be a Java API.

Java.behavior({
    predicate(object) {
        return object instanceof Iterable;
    }
    
    apply(object) {
        object[Symbol.iterator] = *function() {
            let iterator = object.iterator();
            while (iterator.hasNext()) {
                yield iterator.next();
            }
            
            return this;
        }
    }
});

Three types of behaviors will be natively implemented:

• Native Iterable support.

for (const el of javaIterable) {
    console.log(el); 
}

• One-method interfaces will have a constructor to make them from lambdas.

let runnable = new Runnable(() => console.log("Hi!"));

• Interfaces will have a constructor to turn objects into them. Each object will have its own method.

let runnable = new Runnable({
    run() {
        console.log('Hi!');
    }
});