轉載自：https://blog.csdn.net/aitcax/article/details/52694423
1 使用field(效率最高)
long start = System.nanoTime();
Field[] fields = CallCount.class.getDeclaredFields();
for (String str : dateList) {
boolean exist = false;
for (Field field : fields){
field.setAccessible(true);
if (field.getName().endsWith(str)) {
int value = 0;
for (CallCount callCount : callCountList) {
value += (Integer)field.get(callCount);
}
resultList.add(value);
exist = true;
break;
}
}
if (!exist) {
resultList.add(0);
}
}
long end = System.nanoTime();
log.info("old call cost :" + (end-start));
2 使用 org.apache.commons.beanutils.BeanUtils來擷取屬性
long start = System.nanoTime();
for (String str : dateList) {
Integer value = getMinuteAccessCount(str, callCountList);
resultList.add(value);
}
long end = System.nanoTime();
log.info("new call cost :" + (end-start));
private Integer getMinuteAccessCount(String minute, List callCountList) {
Integer result = 0;
String propertyName = "logMinute" + minute;
for (CallCount callCount : callCountList) {
int value = 0;
try {
value = Integer.valueOf(BeanUtils.getProperty(callCount, propertyName));
} catch (NumberFormatException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
e.printStackTrace();
}
result += value;
}
return result;
}
3 使用java.lang.reflect.Method擷取值
long start = System.nanoTime();
for (String str : dateList) {
Integer value = getMinuteAccessCount(str, callCountList);
resultList.add(value);
}
long end = System.nanoTime();
log.info("new call cost :" + (end-start));
private Integer getMinuteAccessCount(String minute, List callCountList) {
Integer result = 0;
for (CallCount callCount : callCountList) {
int value = 0;
try {
Method method = callCount.getClass().getDeclaredMethod("getLogMinute"+minute);
Object obj = method.invoke(callCount);
value = (Integer)obj;
} catch (NumberFormatException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
e.printStackTrace();
}
result += value;
}
return result;
}
4 耗時對比，在使用相同的查詢條件，相同的資料的情況下。通過實驗得到以下兩組資料(耗時/納秒)
1 old call cost :517599
1 old call cost :347916
1 old call cost :337312
1 old call cost :177893
1 old call cost :131709
1 old call cost :82789
1 old call cost :63973
3 new call cost :925383
3 new call cost :794016
3 new call cost :912382
1 old call cost :755016
1 old call cost :365364
1 old call cost :231944
1 old call cost :123498
1 old call cost :103315
1 old call cost :92025
1 old call cost :81762
2 new call cost :139741338
2 new call cost :3387140
2 new call cost :2230497
2 new call cost :9215854
2 new call cost :2313970
2 new call cost :1549374
2 new call cost :1884291
2 new call cost :1100880
2 new call cost :1488138
每組資料前的數字代表之前取值的方式。
由資料對比可以看出，耗時最小的，始終是方式1，并且方式1在多次調用時，耗時是逐漸減少的，可能是有緩存機制。
耗時第二少的是方式3，耗時最多的是方式2.
5 解析
方式1，采用了最基本的java反射方式，使用Filed，循環bean的Field，得到Object，再轉換為Integer類型。
方式2，采用了看似最簡潔的BeanUitls，根據屬性名，擷取屬性值。這樣最耗時。
方式3，采用了擷取bean的Method，然後invoke的方式來擷取值。
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作者：aitcax
來源：CSDN
原文：https://blog.csdn.net/aitcax/article/details/52694423