Build method call from class instance and string?

Question

In Java is it possible to execute a method call given the class instance and the method call saved as a string?

I want to make a sequence of different method calls random so I was going to put the method parts in a list as Strings and shuffle them. How do I then use this string as part of a method call? e.g. myClass.temp below is being treated as a property. If I put the full myClaims. in the List as Objects it will try to execute them there.

List<String> methodList = new ArrayList<String>()
methodList.add("createMethodx(params...)")
methodList.add("createMethody(params...)")
methodList.add("insertMethodz(params...)")

String temp = methodList.get(0)
myClass.temp    //Execute the method.....doesn't work

myClass.temp is the full method call e.g. myClass.createMethodx(param1,param2) — user3668517, May 23 '14 at 10:52
You can randomize a value from a `List` and use reflection to invoke a method corresponding to the given `String`. Although this is probably a very very bad idea design-wise. I would recommend you just randomize any argument given to a single method, whatever your purpose is. — Mena, May 23 '14 at 10:52
what you have added in the list is a String. so how can you expect that it will execute — vikeng21, May 23 '14 at 10:53
possible duplicate of http://stackoverflow.com/questions/160970/how-do-i-invoke-a-java-method-when-given-the-method-name-as-a-string — faisalbhagat, May 23 '14 at 10:54
I've a few different methods that I call that insert data into a database. Each method sets different columns so that's why I kept them separate. I wanted to randomise the order the data goes into the database as part of a testing project. — user3668517, May 23 '14 at 10:58
I added to the List as a string because I thought I might be able to somehow concatenate with the class instance afterwards. Fairly new to Java so never done this before.. — user3668517, May 23 '14 at 11:02

score 0 · Accepted Answer · answered May 23 '14 at 10:55

That's a bad way of doing it. Instead, create a list of Runnable or Callable objects, shuffle that list, and then call the runnables:

final MyClass myClass = ...;
List<Runnable> actions = new ArrayList<>();
actions.add(new Runnable() {
    public void run() {
        myClass.createMethodx(...);
    }
});
actions.add(new Runnable() {
    public void run() {
        myClass.createMethody(...);
    }
});

Collections.shuffle(actions);

for (Runnable action : actions) {
    action.run();
}

With Java 8, that code would become

MyClass myClass = ...;
List<Runnable> actions = new ArrayList<>();
actions.add(() -> myClass.createMethodx(...));
actions.add(() -> myClass.createMethody(...));

Collections.shuffle(actions);

for (Runnable action : actions) {
    action.run();
}

Thanks very much JB - that works for me. That piece of code is great - I would never have been able to do anything like that by myself and it will be really useful. — user3668517, May 23 '14 at 12:17

Build method call from class instance and string?

1 Answers1