Java开发网 - Java 比 C＋＋更快？？？

Topic: Java 比 C＋＋更快？？？

1.Java 比 C＋＋更快？？？	Copy to clipboard
Posted by: lifangning Posted on: 2004-06-17 07:46 程序员一直认为，由于JVM的关系，Java的执行效率低于C/C++…… 但从最近的一则测试表明，Java和C＋＋有得一拼： http://www.sys-con.com/story/?storyid=45250

2.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: floater Posted on: 2004-06-17 09:43 good, glad to know this.

3.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: jigsaw Posted on: 2004-06-17 09:48 这类测试统统很无聊。。。

4.Re:Java 比 C＋＋更快？？？ [Re: jigsaw]	Copy to clipboard
Posted by: aryuan Posted on: 2004-06-17 12:25 快不快重要的是在使用的时候的一种感觉，没人会在意这些数字的。现实一点吧

5.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: julysea Posted on: 2004-06-18 13:53 顶，同意楼上的意见，关键在实际的应用，什么合适就用什么，不单纯是运行速度的事

6.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: hexianmao Posted on: 2004-06-18 15:15 支持，至少从根本上说明。JAVA还是牛的。

7.Re:Java 比 C＋＋更快？？？ [Re: lifangning]

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Posted by: qgjtso
Posted on: 2004-06-18 22:39

java 比C++至少慢动作1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

8.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: xidianliuy Posted on: 2004-06-18 23:31 给我的感觉，在java程序第一次运行时怎么也没有C++快，但当运行同样一个程序10000次时，平均时间还是很快！！！

9.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: lalphbet Posted on: 2004-06-19 17:13 学过编译原理没有？如果没有，去学一学吧~

10.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: stlinuxily Posted on: 2004-06-19 18:50 编译...有原理吗？

11.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: cchuier Posted on: 2004-06-19 20:08 何必呢？发这个帖子还不是心虚 c++现在还是比java快的，事实就是事实无论你怎么说

12.Re:Java 比 C＋＋更快？？？ [Re: lalphbet]

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Posted by: lifangning
Posted on: 2004-06-20 12:34

呵呵，学过编译原理的大哥好牛～～～～
Java在虚拟机上运行，但运行C++的操作系统本身也就是一个虚拟机呀～～
仅靠一些纯理论的纸上谈兵谁不会呀？
有本事去研究研究人家的测试代码，看看人家的测试代码有什么问题，为什么会得到这样的测试结果～～～～～

13.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: floater Posted on: 2004-06-21 05:49 lifangning wrote: 仅靠一些纯理论的纸上谈兵谁不会呀？有本事去研究研究人家的测试代码，看看人家的测试代码有什么问题，为什么会得到这样的测试结果～～～～～ good point!

14.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: samuelxp Posted on: 2004-06-21 09:56 Don't pay so much attention to languages.

15.Re:Java 比 C＋＋更快？？？ [Re: lifangning]

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Posted by: scottding
Posted on: 2004-06-21 16:08

希望大家不要再争论这个无聊的问题了，单就某一个方面根本不具备可比性，无聊的去比较Java和C++那个快，有意义么？Java和C++专注的方面就不同。去比了干什么？做多了这样无聊的比较反而会对一些初学者产生误导，要知道，“快”并不是选择语言的唯一指标！

16.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: Jakie Posted on: 2004-06-21 17:09 同条件下win xp 比 98慢，但还是有人用，你的 386 下的win95 就比p4 下的win xp 快吗？有必要争论吗？！

17.Re:Java 比 C＋＋更快？？？ [Re: lifangning]

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Posted by: nsd
Posted on: 2004-06-22 11:06

Gosling确实这么说过，在某些情况下java的执行速度要超过c++，我当时还以为听错了呢。不过起码能说明这种说法不是空穴来风，无稽之谈什么的。
c和c++，同样是本地代码，但是c程序员就对c++的效率嗤之以鼻。所以不要觉得本地代码都是多么的快。起码我觉得java虚拟机提供的内存管理相对于本地代码来说就是一个很大的优势，没有这个机制的话很难保证很多应用系统的稳固运行。

18.Re:Java 比 C＋＋更快？？？ [Re: lifangning]

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Posted by: guru
Posted on: 2004-06-22 13:23

俺怀疑他的测试结果，我自己做了一个实验，即其中的费波纳切数列的那个例子，结果如下：

Java:

  Command being timed: "java -classpath . fibo 45"
  User time (seconds): 0.01
  System time (seconds): 0.01
  Percent of CPU this job got: 0%
  Elapsed (wall clock) time (h:mm:ss or m:ss): 0:39.79
  Average shared text size (kbytes): 0
  Average unshared data size (kbytes): 0
  Average stack size (kbytes): 0
  Average total size (kbytes): 0
  Maximum resident set size (kbytes): 7680
  Average resident set size (kbytes): 0
  Major (requiring I/O) page faults: 499
  Minor (reclaiming a frame) page faults: 0
  Voluntary context switches: 0
  Involuntary context switches: 0
  Swaps: 0
  File system inputs: 0
  File system outputs: 0
  Socket messages sent: 0
  Socket messages received: 0
  Signals delivered: 0
  Page size (bytes): 4096
  Exit status: 0

CPP:
  Command being timed: "fibo 45"
  User time (seconds): 31.23
  System time (seconds): 0.04
  Percent of CPU this job got: 99%
  Elapsed (wall clock) time (h:mm:ss or m:ss): 0:31.46
  Average shared text size (kbytes): 0
  Average unshared data size (kbytes): 0
  Average stack size (kbytes): 0
  Average total size (kbytes): 0
  Maximum resident set size (kbytes): 13536
  Average resident set size (kbytes): 0
  Major (requiring I/O) page faults: 850
  Minor (reclaiming a frame) page faults: 0
  Voluntary context switches: 0
  Involuntary context switches: 0
  Swaps: 0
  File system inputs: 0
  File system outputs: 0
  Socket messages sent: 0
  Socket messages received: 0
  Signals delivered: 0
  Page size (bytes): 4096
  Exit status: 0

多次测试的结果与此上述结果类似，都是CPP快于Java。

19.Re:Java 比 C＋＋更快？？？ [Re: nsd]	Copy to clipboard
Posted by: samuelxp Posted on: 2004-06-23 09:39 nsd wrote: ...起码我觉得java虚拟机提供的内存管理相对于本地代码来说就是一个很大的优势，没有这个机制的话很难保证很多应用系统的稳固运行。对于你这句话非常之不赞同。

20.Re:Java 比 C＋＋更快？？？ [Re: stlinuxily]	Copy to clipboard
Posted by: kam Posted on: 2004-06-23 10:34 stlinuxily wrote: 编译...有原理吗？ Compiler must faster then Interpreter-Compiler JVM is an example of Interpreter-Compiler. ^.^ But ofcoz, we many always enhance the programming logic to archieve a better runtime. ^.^

21.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: violin Posted on: 2004-06-24 15:58 感觉还是慢了，

22.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: tzutolin Posted on: 2004-06-25 08:27 這類的報告, 若能找出一篇, 那麼, 結果相反的報告, 至少便能找出十篇. Java, 究竟還是比 C++ 慢. 不過, 仍然很感謝提供這些資訊的人, 讓學 Java 的朋友能夠開懷. Best Regards, tzutolin

23.Re:Java 比 C＋＋更快？？？ [Re: lifangning]

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Posted by: samuelxp
Posted on: 2004-07-19 11:51

lifangning wrote:
呵呵，学过编译原理的大哥好牛～～～～
Java在虚拟机上运行，但运行C++的操作系统本身也就是一个虚拟机呀～～
仅靠一些纯理论的纸上谈兵谁不会呀？
有本事去研究研究人家的测试代码，看看人家的测试代码有什么问题，为什么会得到这样的测试结果～～～～～

操作系统不是虚拟机。
硬件实现虚拟机和软件实现差别是很大地。

24.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: colo007 Posted on: 2004-07-20 17:07 floater又出现了？

25.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: RollingWoods Posted on: 2004-07-23 20:35 到CPU的Cache里，都是机器码，有什么可比的。

26.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: janage Posted on: 2004-07-25 14:39 快与慢都是相对的。有必要这样比吗？一个Java高手去写C++的程序与他写出来的Java相比，C++能快吗？ Java字节码是要通过JVM解释才能运行在CPU上的，而C++是直接运行在CPU上面的。但如果C++的程序结构不行，自然快不起来！

27.Re:Java 比 C＋＋更快？？？ [Re: lifangning]

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Posted by: javaslave
Posted on: 2004-07-25 20:29

this topic has been discussed so many times on http://forum.java.sun.com, just do a search at the New to Java Tech. forum if u'd like to know more about it. To sum up, for the language itself, without any doubt, C++ is faster than Java. But we often have to consider many other factors as well for any application's execution speed, for instance, hardware's performance, network status if the app. is a distributed system. Personally, i dont think it makes much sense if we just take it completely out of context and talk about their execution speed alone.

28.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: dreamchenwen Posted on: 2004-07-25 22:35 我觉得没有要比较的必要啊。所谓各有千秋阿。

29.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: michaelbeyond Posted on: 2004-07-26 10:11 普通应用来说一点意义都没有，真的到了大型系统，纯粹的编程语言也是没有用的，还要看应用的架构设计，算法设计，和编程等等一切相关联的问题，这样就更没有什么好比较的问题了，有时候速度并不是所需要的，还要看能否解决问题。

30.Re:Java 比 C＋＋更快？？？ [Re: lifangning]	Copy to clipboard
Posted by: GWoo Posted on: 2004-07-27 17:09 对于Web应用来说，网速的快慢才是影响用户感觉的关键