methodpointertest.java

这个是我老师给的Java核心技术1的第5章源代码

/**
   @version 1.1 2004-02-21
   @author Cay Horstmann
*/

import java.lang.reflect.*;

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);

      // construct formatter to print with 4 digits precision

      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(); }
      }
   }
}