corejava第7版

corejava第7版/v1/v1ch5/MethodPointerTest/MethodPointerTest.java

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+/**
+   @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);
+
+      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(); }
+      }
+   }
+}