How to call functions in bulk with Java reflection

Call the function in a variable by reflection.

The class you want to call. Only four arithmetic operations are performed appropriately.

Calc.java

package refrectiontest;

public class Calc {

    public int plus(int a, int b) {
        return a + b;
    }
        public int minus(int a, int b) {
        return a - b;
    }
        public int multiply(int a, int b) {
        return a * b;
    }
        public int divide(int a, int b) {
        return a / b;
    }
        
}

Where to call.

RefrectionTest.java

package refrectiontest;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;


public class RefrectionTest {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try {
            //Create an instance
            Constructor<?> cons = Calc.class.getConstructor();
            Calc calc = (Calc) cons.newInstance();
            //Register the function name you want to use in the list
            List<String> methodNames = new ArrayList<>();
            methodNames.add("plus");
            methodNames.add("minus");
            methodNames.add("multiply");
            methodNames.add("divide");
            //Call functions collectively with the registered name.
            //If the caller's signature is different, it is necessary to branch inside or separate the for statement.
            for(String methodName : methodNames){
                //Get a function pointer in a Method type variable.
                //getMethod(Class instance created above,1st argument, 2nd argument, 3rd ...) of the function you want to use
                //Method1 for as many signatures as you want to use,Define it as method2.
                Method method = (Calc.class.getMethod(methodName,int.class,int.class));
                //Use of functions. Since the return value of invoke is Object type, cast it according to the target function.
                int result = (int)method.invoke(calc,20,10);
                System.out.println(methodName + " = " + result );

            }

        } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException | InstantiationException ex) {
            Logger.getLogger(RefrectionTest.class.getName()).log(Level.SEVERE, null, ex);
        }
        
    }
    
}

Output result plus = 30 minus = 10 multiply = 200 divide = 2

Usage

It may be useful when the method is specified as a String type. In this example, methodNames are added one by one by hand, The function names you want to call are method1, method2, method3, method4 ... If it is a serial number like

for(int i = 1;i<10;i++){
    "method" + String.valuOf(i) ;
}

You may be able to measure the shortening of the code if it is automatically generated like this.