计算Java中任意一个方法的执行时间的工具类
如何获取一个方法的执行时间，不论是静态方法还是静态方法，不论是私有方法还是共有方法，如果该对象不能
被实例化，使用该对象的class对象也可以，例如Arrays.class也可以作为bean传入方法中
只有当方法是static，使用bean和bean.class都可以，但如果不是static，你使用bean.class 会报错
该方法主要用来计算一个方法的执行时间和是否打印方法的执行时间和输出结果，我制作这个方法主要用来比较排序算法的时间复杂度
下面是工具类的代码：
1 package algorithm.study.utils;
2
3 import java.lang.reflect.Method;
4
5 /**
6 * This class is getting a method execute time and provide some other functions.
7 *
8 * @author ygh 2017年2月24日
9 */
10 public class MethodExecuteTimeUtils {
11
12 /**
13 * Get a method execute time using millisecond and cancel method's print return result and
14 * execute time.
15 *
16 * @param bean The method is in this bean
17 * @param params The parameter the method execute need
18 * @param methodName The name of the method
19 * @param types The parameter type of the method
20 * @return The execute time of this method
21 * @throws Exception If <code>getMethod</code> or <code>invoke</code> fail.
22 */
23 public static long getMethodExecuteTime(Object bean, Object[] params, String methodName, Class<?>[] types)
24 throws Exception {
25 return getMethodExecuteTime(bean, params, methodName, types, false, false);
26 }
27
28 /**
29 * Get a method execute time using millisecond and cancel print method's return result.
30 *
31 * @param bean The method is in this bean
32 * @param params The parameter the method execute need
33 * @param methodName The name of the method
34 * @param types The parameter type of the method
35 * @param isPrintExecutetime Whether print the execute time in console, true is print false not
36 * @param isViewMehtodResult Whether print the return result in console, true is print false not
37 * @return The execute time of this method
38 * @throws Exception If <code>getMethod</code> or <code>invoke</code> fail.
39 */
40 public static long getMethodExecuteTime(Object bean, Object[] params, String methodName,
41 Class<?>[] types, boolean isPrintExecutetime) throws Exception {
42 return getMethodExecuteTime(bean, params, methodName, types, isPrintExecutetime, false);
43 }
44
45 /**
46 * Get a method execute time using millisecond and add some other service.
47 *
48 * @param bean The method is in this bean
49 * @param params The parameter the method execute need
50 * @param methodName The name of the method
51 * @param types The parameter type of the method
52 * @param isPrintExecutetime Whether print the execute time in console, true is print false not
53 * @param isViewMehtodResult Whether print the return result in console, true is print false not
54 * @return The execute time of this method
55 * @throws Exception If <code>getMethod</code> or <code>invoke</code> fail.
56 */
57 public static long getMethodExecuteTime(Object bean, Object[] params, String methodName,
58 Class<?>[] types, boolean isPrintExecutetime, boolean isViewMehtodResult) throws Exception {
59 Class<?> clazz;
60 long executeTime = -1L;
61 boolean isAccessiable = false;
62 Method method = null;
63 if (bean instanceof Class<?>) {
64 clazz = (Class<?>) bean;
65 } else {
66 clazz = bean.getClass();
67 }
68 try {
69 if (types == null) {
70 method = clazz.getDeclaredMethod(methodName);
71 } else {
72 method = clazz.getDeclaredMethod(methodName, types);
73 }
74 isAccessiable = method.isAccessible();
75 if (!isAccessiable) {
76 method.setAccessible(true);
77 }
78
79 if (isViewMehtodResult) {
80 executeTime = getReturnMethodExecuteTime(bean, params, method);
81 } else {
82 executeTime = getMethodExecuteTime(bean, params, method);
83 }
84 method.setAccessible(isAccessiable);
85 if (isPrintExecutetime) {
86 printExecute(clazz, methodName, executeTime);
87 }
88 } catch (Exception e) {
89 throw new Exception("excute method fail");
90 }
91 return executeTime;
92 }
93
94 /**
95 * Get a method execute time, use millisecond. We don't think the method whether has a return
96 * result
97 *
98 * @param bean The method is in this bean
99 * @param params The parameters the method execute need
100 * @param method The Method entity
101 * @return The millisecond the method execute spend
102 * @throws Exception If the method invoke fail
103 */
104 private static long getMethodExecuteTime(Object bean, Object[] params, Method method) throws Exception {
105 long startTime = System.currentTimeMillis();
106 method.invoke(bean, params);
107 long endTime = System.currentTimeMillis();
108 return endTime - startTime;
109 }
110
111 /**
112 * Get a method execute time, use millisecond. The method must has a return result will input
113 * the return result in console ,If the method has not return result, please call
114 * <code>getMethodExecuteTime</code> method.
115 *
116 * @param bean The method is in this bean
117 * @param params The parameters the method execute need
118 * @param method The Method entity
119 * @return The millisecond the method execute spend
120 * @throws Exception If the method invoke fail
121 */
122 private static long getReturnMethodExecuteTime(Object bean, Object[] params, Method method)
123 throws Exception {
124 long startTime = System.currentTimeMillis();
125 Object result = (Object) method.invoke(bean, params);
126 long endTime = System.currentTimeMillis();
127 if (result != null) {
128 System.out.println("result input：" + result.toString());
129 } else {
130 System.out.println("Warning:" + bean.getClass().getName() + "." + method.getName()
131 + "has not return " + "result,please setting the isViewMehtodResult as false");
132 }
133 return endTime - startTime;
134 }
135
136 /**
137 * Print the execute time of method
138 *
139 * @param methodName The name of the method
140 * @param time The execute of the method
141 */
142 public static void printExecute(Class<?> clazz, String methodName, long time) {
143 System.out.println(clazz.getName() + "." + methodName + " execute time: " + time);
144 }
145 }Person类，用于测试：
1 package javareflect.demo;
2 /**
3 * This a person domain used test java.reflect
4 * @author ygh
5 * 2017年2月26日
6 */
7 public class Person {
8
9 private String name;
10
11 private Integer age;
12
13 private static String gender;
14
15 public static String getGender(){
16 return gender;
17 }
18
19 public static void setGender(String gender){
20 System.out.println("性别："+gender);
21 }
22
23 public String getName() {
24 return name;
25 }
26
27 public void setName(String name) {
28 this.name = name;
29 }
30
31 public Integer getAge() {
32 return age;
33 }
34
35 public void setAge(Integer age) {
36 this.age = age;
37 }
38
39 public static void fun1(){
40 System.out.println("this is fun1");
41 }
42
43 private void fun2(){
44 System.out.println("this is private method");
45 }
46
47
48 }下面是测试代码：测试执行Person类里面的各种Method，静态的，私有的，共有的
1 public class ReflectTest {
2 @Test
3 public void fun1() throws Exception {
4 Person person = new Person();
5 Object[] params = null;
6 Class<?>[] types = null;
7 MethodExecuteTimeUtils.getMethodExecuteTime(person, params, "fun2", types, true, true);
8 }
9 @Test
10 public void fun2() throws Exception {
11 Person person = new Person();
12 Object[] params = null;
13 Class<?>[] types = null;
14 MethodExecuteTimeUtils.getMethodExecuteTime(person, params, "fun1", types, true, true);
15 }
16 @Test
17 public void fun3() throws Exception {
18 Person person = new Person();
19 Object[] params = {12};
20 Class<?>[] types = {Integer.class};
21 MethodExecuteTimeUtils.getMethodExecuteTime(person, params, "setAge", types, true, true);
22 System.out.println(person.getAge());
23 }
24 }下面是测试代码，比较Java自带的排序方法和归并排序哪个时间复杂度更高。
1 package algorithm.study.demo2;
2
3
4 import java.util.Arrays;
5
6 import org.junit.Test;
7
8 import algorithm.study.utils.MethodExecuteTimeUtils;
9
10 /**
11 * This class implement MergeSort
12 * @author ygh
13 * 2017年2月23日
14 */
15 public class MergeSort {
16
17 /**
18 * Arithmetic thoughts:
19 * If we want to sort a array elements,we can sort their left,then
20 * sort their right. In the left array, we can use same thought
21 * separate the left array to halt then sort them.....
22 * At last,it will change into tow number compare,then merge
23 *
24 * @param arr The array need to sort
25 * @param A temporary array to store elements that have sorted,its length is right-left
26 *
27 * @param left The left index of elements you want to sort in this array
28 * @param right The right index of elements you want to sort in this array
29 */
30 public void mergeSort(int[] sortedArr,int[] tmpArr,int left,int right){
31 if(left<right){
32 int mid = (left+right) / 2;
33 mergeSort(sortedArr,tmpArr, left, mid);
34 mergeSort(sortedArr,tmpArr, mid+1, right);
35 merge(sortedArr, tmpArr,left,mid,right);
36 copy(sortedArr, tmpArr,left,right);
37 }
38 }
39
40 /**
41 * Copy elements from temporary array to sorted array. The index range is from left to rigth
42 * @param haltSortedArr The array need to sort
43 * @param tmpArr The temporary array
44 * @param left The left index
45 * @param right The right index
46 */
47 private void copy(int[] haltSortedArr, int[] tmpArr, int left, int right) {
48 for(int i=left;i<=right;i++){
49 haltSortedArr[i]=tmpArr[i];
50 }
51 }
52
53 /**
54 * This method is to merge elements from haltSortedArr.now the haltSortedArr
55 * has became sorted half by half.The elements' index from left to mid is sorted,and the
56 * elements' index from mid to right is sorted.So we just need to merge it to get all order
57 * array
58 * @param haltSortedArr The array has became sorted half by half
59 * @param tmpArr A temporary array to store elements order.
60 * @param left The left index of elements you want to sort in this array
61 * @param mid The order element separator index
62 * @param right The right index of elements you want to sort in this array
63 */
64 private void merge(int[] haltSortedArr, int[] tmpArr, int left, int mid, int right) {
65 int i=left;
66 int j=mid+1;
67 int d = left;
68 while (i <= mid && j <= right) {
69 if (haltSortedArr[i] <= haltSortedArr[j]) {
70 tmpArr[d++]=haltSortedArr[i++];
71 }else{
72 tmpArr[d++]=haltSortedArr[j++];
73 }
74 }
75
76 if(i>mid){//If i more mid,indicate some elements have not be put in temporary array in array right
77 while(j<=right){
78 tmpArr[d++]=haltSortedArr[j++];
79 }
80 }else{//If i less mid,indicate some elements have not be put in temporary array in array left
81 while(i<=mid){
82 tmpArr[d++]=haltSortedArr[i++];
83 }
84 }
85 }
86
87
88 /**
89 * Get a random array by size and max value
90 * @param size The size the new array you want to create
91 * @param maxValue The max value in the array;
92 * @return A randow array
93 */
94 private int[] getRandomArray(int size,int maxValue){
95 int []arr = new int[size];
96 for(int i=0;i<size;i++){
97 arr[i]=getIntRandomValue(maxValue);
98 }
99 return arr;
100 }
101
102 /**
103 * Get a random that less than max value
104 * @param maxValue The max value you get the random number
105 * @return A random number less than max value
106 */
107 private int getIntRandomValue(int maxValue){
108 return (int) (Math.random()*maxValue);
109 }
110
111
112 /**
113 * This is a method to test how long time the mergeSort spend on
114 * @param arr The array need to sort
115 * @throws Exception
116 */
117 public void testMergeSort(int[] arr) throws Exception{
118 MergeSort m = new MergeSort();
119 Class<?>[] types = {int[].class,int[].class,int.class,int.class};
120 String methodName = "mergeSort";
121 int size = arr.length-1;
122 int[] tmp = new int[size];
123 mergeSort(arr, tmp, 0, size-1);
124 Object[] params={arr,tmp,0,size-1};
125 MethodExecuteTimeUtils.getMethodExecuteTime(m, params,methodName,types,true);
126 }
127
128 /**
129 * This is a method to test how long time the javaself sort method spend on
130 * @param arr The array need to sort
131 * @throws Exception
132 */
133 public void testJavaSort(int[] arr) throws Exception{
134 Class<?>[] types = {int[].class};
135 String methodName = "sort";
136 Object[] params = {arr};
137 //although Arrays can be instance,you use Arrays.class also available,and static method also available
138 MethodExecuteTimeUtils.getMethodExecuteTime(Arrays.class, params, methodName, types,true);
139 }
140
141 /**
142 * print array into console
143 * @param arr The array need to print console
144 */
145 public void printArray(int[] arr){
146 System.out.println(Arrays.toString(arr));
147 }
148
149 /**
150 * This is just a test method
151 * @throws Exception
152 */
153 @Test
154 public void fun3() throws Exception{
155 int size = 922000;
156 int maxValue = 9999999;
157 //construct random array
158 int[] arr1 = getRandomArray(size, maxValue);
159 int[] arr2 = Arrays.copyOf(arr1, size);
160 testMergeSort(arr2);
161 testJavaSort(arr1);
162 }
163
164
165
166
167 }