统计方法运行时间【Java实现】

使用命令模式和适配器模式实现方法运行时间的统计：

 

 

 

 

 

代码实现如下：

 

接口Command：定义命令的执行操作

 

package common;public interface Command {// 运行方法void run();}

 

CommandRuntime 类:统计命令运行时间，使用命令模式

 

package common;public class CommandRuntime {private Command command;public CommandRuntime(Command command) {this.command = command;}public long runtime() {long start = System.currentTimeMillis();command.run();long end = System.currentTimeMillis();return end-start;}}

 CombinationCommand:  解决组合问题的命令， 采用类适配器模式：

 

package algorithm.problems;import algorithm.permutation.Combination;import common.Command;public class CombinationCommand extends Combination implements Command {public CombinationCommand(int n) {super(n);}public void run() {solution();}}

CombinationRuntime: 测量组合问题的运行时间

 

package algorithm.problems;import java.io.BufferedWriter;import java.io.FileWriter;import java.io.IOException;import common.CommandRuntime;public class CombinationRuntime {public static void main(String[] args){try {BufferedWriter fileWriter = new BufferedWriter(new FileWriter("runtime.txt"));fileWriter.write("runtime: ");fileWriter.newLine();for (int i=1; i < 30; i++) {   CommandRuntime comRuntime = new CommandRuntime(new CombinationCommand(i));   long runtime = comRuntime.runtime();   fileWriter.write( "n = " + i + " : " + runtime + " ms");   fileWriter.newLine();}System.out.println("over.");fileWriter.close();} catch (IOException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();}}}

 

另外一种使用反射机制实现的运行时间测量框架：

 

package common;import java.lang.reflect.Constructor;import java.lang.reflect.Method;public class RuntimeMeasurement {public RuntimeMeasurement(int maxsize) {this.maxsize = maxsize;time = new double[maxsize];}// 问题最大规模: 以 10 的 size 次幂计private int maxsize ;// 运行时间以 ms 计private double[] time ;/** * measureTime : 对指定类型的对象调用指定参数列表的指定方法，并测量其运行时间 * @param type  指定对象类型，必须有一个 参数类型为 int 的公共构造器方法 * @param methodName  指定测试方法名称，要求是空参数列表 */public void measureTime(Class<?> type, String methodName){try { Constructor<?> con = type.getConstructor(int.class); Method testMethod = null;     for (int i = 0; i < time.length; i++) {      Object obj = con.newInstance(power10(i+1));  testMethod = type.getMethod(methodName, new Class<?>[]{});  long start = System.nanoTime();    testMethod.invoke(obj, new Object[] {});  long end = System.nanoTime();  time[i] =  ((end - start) / (double)1000000) ;       }      } catch (Exception e) {e.printStackTrace();System.out.println(e.getMessage());}}/** * showTime : 显示已经测量获得的运行时间，在 measureTime 方法调用后调用该方法。 */public void showTime(){for (int i=0; i < time.length; i++) {System.out.printf("n = %12d : " , power10(i+1));System.out.printf("%12.3f\n", time[i]);}}private int power10(int n){int result = 1;while (n > 0) {result *= 10;n--;}return result;}}