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;
} }