How to call methods in random order(Java JDK11)?

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class Scratch {

    public void meth1(){

    }
    public void meth2(){

    }
    public void meth3(){

    }
    public void meth4(){

    }
    public void meth5(){

    }
    public static void main(String[] args) {
        int randomNumber=(int)Math.random()*5;
    }
}

Here I have 5 methods, and I want to call them randomly. I am new to OOP but know a bit about C, in that case I would've stored the addresses of the functions(methods) in an array, generate a random number between [0,4] and call the functions using the array in random order. But in Java, I don't know how to get the memory address of a method. How should I do that?

java-11 memory-address pointers methods java
3 Answers

You do this with a "function-variable" of type Runnable and its method Runnable#run.

Scratch s = new Scratch();
List<Runnable> methods = new ArrayList<>();
methods.add(s::meth1); // this is how you reference a method itself
methods.add(s::meth2);
...
methods.get(1).run(); // this is how you "tell" the Runnable to execute its code

The abstract method run is overriden with the code you have, so this is a "reference" to call your method. In the package java.util.function you can find many classes that can be used in case your method has parameters or/and a return-value.

Now calling a random method from the list is pretty simple:

int randomNumber = new Random().nextInt(methods.size());
methods.get(randomNumber).run();
user_123232480

the easiest way would be to put your methods in a switch statement and get a random value that way:

class Scratch {

    public void meth1(){

    }
    public void meth2(){

    }
    public void meth3(){

    }
    public void meth4(){

    }
    public void meth5(){

    }
    public static void main(String[] args) {
      Random r = new Random();
      Scratch scratch = new Scratch();
      int num = r.nextInt(5);
      switch(num) {
        case 0:
          scratch.meth1();
          break;
        case 1:
          scratch.meth2();
          break;
        case 2:
          scratch.meth3();
          break;
        case 3:
          scratch.meth4();
          break;
        case 4:
          scratch.meth5();
          break;
      }
    }
}
user_18309160

This is a little tedious, but you can set a certain range to a method. For example:

public static void main(String[] args) {
    int rand=(int)Math.random()*5;

    if(rand < 0.1) {
        meth1();
    } else if(rand < 0.2) {
       meth2();
    } else if(rand < 0.3) {
       //etc...
    }
}
user_118662490
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