Java和Python运行速度对比：同一个函数运行一百万次，Java耗时0.577秒，Python耗时78秒--135倍的差距。
版本：Java 8,Python 2.7.10
Java测试代码：
import java.util.Date;
public class test
{
public static void main(String[] args)
{
Date start = new Date();
for (int i = 0; i < 1000000; i++)
{
transform();
}
Date end = new Date();
long diff = end.getTime() - start.getTime();
System.out.println("it takes "+diff/1000.00+" seconds");
}
public static void transform()
{
String str = "Pcybgle rfgq rsrmpgyj fyq npmzyzjw pcgldmpacb wmsp glrcpcqr gl sqgle Nwrfml - wms qfmsjb zc cyecp rm ynnjw Nwrfml rm qmjtgle wmsp pcyj-umpjb npmzjckq. Ufcpc qfmsjb wms em rm jcypl kmpc?";
for (int i = 0; i < str.length(); i++)
{
char c = str.charAt(i);
if (c >= 'a' && c <= 'z')
{
c += 2;
if (c > 'z')
{
c -= 26;
}
System.out.print(c);
}
else if (c >= 'A' && c <= 'Z')
{
c += 2;
if (c > 'Z')
{
c -= 26;
}
System.out.print(c);
}
else
System.out.print(c);
}
}
}
Python测试代码：
import sys,datetime
def transform():
str='''Pcybgle rfgq rsrmpgyj fyq npmzyzjw pcgldmpacb wmsp glrcpcqr gl sqgle Nwrfml - wms qfmsjb zc cyecp rm ynnjw Nwrfml rm qmjtgle wmsp pcyj-umpjb npmzjckq. Ufcpc qfmsjb wms em rm jcypl kmpc?'''
for s in str:
if ord(s)>=ord('a') and ord(s)<=ord('z'):
new=ord(s)+2
if new>ord('z'):
new-=26
sys.stdout.write(chr(new))
elif ord(s)>=ord('A') and ord(s)<=ord('Z'):
new=ord(s)+2
if new>ord('Z'):
new-=26
sys.stdout.write(chr(new))
else:
sys.stdout.write(s)
starttime = datetime.datetime.now()
for i in range(1000000):
transform()
endtime = datetime.datetime.now()
print 'it takes %s seconds'%(endtime - starttime).seconds