public void test1(){};
public void test2(){};
public void test3(){};

If (main.rand.nextInt(3) == x)

package com.example;

import java.util.Random;
import java.lang.reflect.Method;

class Test {
    public void test1() {}
    public void test2() {}
    public void test3() {}
}

public class Main {
    public static void main(String args[]) throws ReflectiveOperationException {
        Random rnd = new Random();

        String methodName = "test" + (rnd.nextInt(3) + 1);

        Class<?> cls = Class.forName("com.example.Test");
        Object obj = cls.newInstance();

        Method method = cls.getDeclaredMethod(methodName);
        method.invoke(obj);
    }
}

public class Test
{
    public void test1() { System.out.println("1"); };
    public void test2() { System.out.println("2"); };
    public void test3() { System.out.println("3"); };

    public static void main(String[] args)
    {
        Test t = new Test();
        Runnable[] methods = { t::test1, t::test2, t::test3 };
        Random random = new Random();
        Runnable method = methods[random.nextInt(methods.length)];
        method.run();
    }
}