What are the different ways to call methods dynamically in java

Question

Interface:

interface A
{
   void run(String methName);
}

Classs:

class X implements A
{
    void run(String methName)
    {

    }
    void m1()
    {

    }
    void m2()
    {
    }
    void m3()
    {

    }

}

I want to invoke m1, m2 and m3 methods by name dynamically from run method without using reflection mechanism

Please explain what you mean with "dynamically" and why reflection is not an option. — sigget, Mar 11 '16 at 13:10
dynamically in the sense we are passing method name as parameter, — Mahender Ambala, Mar 11 '16 at 13:22

Andy Turner · Answer 1 · 2016-03-11T13:14:54.227

2

Don't overthink it:

switch (methName) {
  case "m1": m1(); break;
  case "m2": m2(); break;
  case "m3": m3(); break;
  default: throw new AssertionError();
}

If you want to do something a bit safer, you can define a strategy enum, something like:

enum Strategy {
  M1 { @Override public void run(X instance) { instance.m1(); } },
  M2 { @Override public void run(X instance) { instance.m2(); } },
  M3 { @Override public void run(X instance) { instance.m3(); } };

  public abstract void run(X instance);
}

then

 void run(Strategy strategy) {
   strategy.run(this);
 }

Now you can't pass in an arbitrary method name, but are limited to an instance of Strategy.

edited Mar 11 '16 at 13:14

answered Mar 11 '16 at 13:10

Andy Turner

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I only notice this now, but calling it "meth" is... an interesting decision – Idos Mar 11 '16 at 13:11
here we are hard coding but if we have 20 methods then what we will do? – Mahender Ambala Mar 11 '16 at 13:18
1

Copy and paste those lines 20 times and move on with your life :) – Andy Turner Mar 11 '16 at 13:18
3

Or use reflection. – Andy Turner Mar 11 '16 at 13:28

score 1 · Answer 2 · edited May 23 '17 at 11:59

1

As stated in this post,

Reflection is a language's ability to inspect and dynamically call classes, methods, attributes, etc. at runtime.

So saying that you want to perform reflection without reflection makes no sense.

edited May 23 '17 at 11:59

Community

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1

answered Mar 11 '16 at 13:11

What are the different ways to call methods dynamically in java

2 Answers2