Java代碼執(zhí)行效率問題

效率是一樣的，雖然語句不一樣，但是編譯成class文件后，都是相同的JVM指令。

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新建一個Java文件Test2.java，然后把它編譯成Test2.class

public class Test2 {

public static boolean stringIsNull(String str) {

if (str == null)

return true;

return false;

}

public static boolean stringIsNull2(String str) {

if (str == null)

return true;

else

return false;

}

public static boolean stringIsNull3(String str) {

return str == null;

}

}

然后你可以通過JDK自帶的javap命令查看JVM指令，三個方法的JVM指令是一樣的

JAVA安裝目錄/bin/javap -c Test2

Compiled from "Test2.java"

public class Test2 extends java.lang.Object{

public Test2();

Code:

0: aload_0

1: invokespecial #1; //Method java/lang/Object."init":()V

4: return

public static boolean stringIsNull(java.lang.String);

Code:

0: aload_0

1: ifnonnull 6

4: iconst_1

5: ireturn

6: iconst_0

7: ireturn

public static boolean stringIsNull2(java.lang.String);

Code:

0: aload_0

1: ifnonnull 6

4: iconst_1

5: ireturn

6: iconst_0

7: ireturn

public static boolean stringIsNull3(java.lang.String);

Code:

0: aload_0

1: ifnonnull 8

4: iconst_1

5: goto 9

8: iconst_0

9: ireturn

}

田忌賽馬C++程序源代碼 不用class的

#include?iostream

#include?string

#include?vector

#include?algorithm

#include?time.h

const?std::string?GetGongziHorse(std::vectorstd::string?horse)

{

int?size?=?horse.size();

int?choose?=?rand()%size;

std::string?horseChoosed?=?horse[choose];

std::vectorstd::string::iterator?it?

=?find(horse.begin(),?horse.end(),?horseChoosed);

horse.erase(it);

return?horseChoosed;

}

const?std::string?GetTianjiHorse(const?std::string?horseChoosed)

{

if?(strcmp(horseChoosed.c_str(),?"千里馬")?==?0)

return?"劣馬";

else?if?(strcmp(horseChoosed.c_str(),?"好馬")?==?0)

return?"千里馬";

else

return?"好馬";

}

int?main(void)

{

srand(time(NULL));

std::string?strHorse[]?=?{"千里馬",?"好馬",?"劣馬"};

std::vectorstd::string?horseGongzi;

horseGongzi.insert(horseGongzi.end(),?strHorse,?strHorse?+?3);

int?i?=?1;

while(horseGongzi.size())

{

std::string?horseChoosed?=?GetGongziHorse(horseGongzi);

std::cout??"第"??i??"場"??std::endl;

std::cout??"虛空公子派出了："??horseChoosed??std::endl;

std::cout??"田忌派出了："?

GetTianjiHorse(horseChoosed)??std::endl;

i++;

std::cout??std::endl;

}

std::cout??"田忌無恥的贏了"??std::endl;

getchar();

return?0;?

}

用c語言寫出田忌賽馬的流程圖和程序

根據(jù)流程圖，我寫了一個完整的程序給你參考。

源代碼如下（vc++6.0下編譯通過）：

#include stdio.h

int main(void)

{

int x=0,max=0,min=0,i=0,s=0;

printf("please input a number(x): \n");

scanf("%d", x);

max = x;

min = x;