The JNI test-java calls the C algorithm and returns the 1 to 20 factorial of the Java call and

One, Java side:

Define the native method, ' public native long factorial (int n); ', the method is implemented in C + +, computes ' 1 to 20 factorial and ', the argument ' int n ' is the factorial of the first n and (here is 20). Returns the result of the calculation, and return to the Java call.

The code is:

1  Public classFactorialjava {2 3      Public native LongFactorial (intn);4 5     //evaluate the elapse time.and the execution result.6      Public Longelapse () {7         LongStart =System.currenttimemillis ();8 9         //code executing time.Ten         LongSumresult = factorial (20); One  ASystem.out.println ("Sum_result:" +sumresult); -  -         LongEnd =System.currenttimemillis (); the         returnEnd-start; -     } -  -     //load the DLL library before executing conductive code. +     Static { -System.loadlibrary ("Factorialdll"); +     } A  at      Public Static voidMain (string[] args) { -Factorialjava FAC =NewFactorialjava (); -System.out.println ("Time-consuming:" + fac.elapse () + "milliseconds"); -     } -  -}

View Code

b/C + + creates a project in VS that can generate DLL dynamic-link libraries and implements the native method defined in Java. The code is as follows:

1 Jlong2 Recesive_fac (jint N) {3     if(n = = 1)4         return1;5     Else6     {7         returnn * RECESIVE_FAC (n-1);8     }9 }Ten  One //Use the JNI loop recursion procedure to return the result to the Java call. A jniexport jlong jnicall java_factorialjava_factorial -(JNIENV *env, Jobject obj, Jint N) { -Jlong sum = 0;  the     //const Jint n =; -      for(inti = 1; I <= N; i++) { -Sum + =RECESIVE_FAC (i); -     } +      -     returnsum; +}

View Code

Where the calling process needs to introduce additional header files, configure the classpath steps in Eclipse in the blog with the implementation of Java JNI (1)-and further deepen the understanding of the JVM implementation.

The JNI test-java calls the C algorithm and returns the 1 to 20 factorial of the Java call and