Invoking Methods Through Reflection in Java

Invoke Methods Through Reflection in Java

import java.lang.reflect.*;

/**

* This program shows how to invoke methods through reflection.

*/

public class MethodPointerTest

{

public static void main(String[] args) throws Exception

{

// get method pointers to the square and sqrt methods

Method square = MethodPointerTest.class.getMethod("square", double.class);

Method sqrt = Math.class.getMethod("sqrt", double.class);

// print tables of x- and y-values

printTable(1, 10, 10, square);

printTable(1, 10, 10, sqrt);

}

/**

* Returns the square of a number

* @param x a number

* @return x squared

*/

public static double square(double x)

{

return x * x;

}

/**

* Prints a table with x- and y-values for a method

* @param from the lower bound for the x-values

* @param to the upper bound for the x-values

* @param n the number of rows in the table

* @param f a method with a double parameter and double return value

*/

public static void printTable(double from, double to, int n, Method f)

{

// print out the method as table header

System.out.println(f);

double dx = (to - from) / (n - 1);

for (double x = from; x <= to; x += dx)

{

try

{

double y = (Double) f.invoke(null, x);

System.out.printf("%10.4f | %10.4f%n", x, y);

}

catch (Exception e)

{

e.printStackTrace();

}

}

}

}

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