JNI | Returning an Array

ArrayRet.java

   1 public class ArrayRet{
   2         public native int[][] rand2DArray(int size);
   3 
   4         public static void main(String args[]){
   5                 ArrayRet jniAr=new ArrayRet();
   6                 System.loadLibrary("randomintdll");
   7                 
   8                 int randArr[][]=jniAr.rand2DArray(3);
   9                 for(int i=0;i<3;i++){
  10                         for(int j=0;j<3;j++){
  11                                 System.out.print(" " + randArr[i][j]);
  12                         }
  13                         System.out.println();
  14                 }
  15                 
  16         }
  17 }

ArrayRet.h

   1 /* DO NOT EDIT THIS FILE - it is machine generated */
   2 #include <jni.h>
   3 /* Header for class ArrayRet */
   4 
   5 #ifndef _Included_ArrayRet
   6 #define _Included_ArrayRet
   7 #ifdef __cplusplus
   8 extern "C" {
   9 #endif
  10 /*
  11  * Class:     ArrayRet
  12  * Method:    rand2DArray
  13  * Signature: (I)[[I
  14  */
  15 JNIEXPORT jobjectArray JNICALL Java_ArrayRet_rand2DArray
  16   (JNIEnv *, jobject, jint);
  17 
  18 #ifdef __cplusplus
  19 }
  20 #endif
  21 #endif

ArrayRet.cpp

   1 #include "ArrayRet.h"
   2 #include <time.h>
   3 #include <stdlib.h>
   4 
   5 JNIEXPORT jobjectArray JNICALL Java_ArrayRet_rand2DArray
   6   (JNIEnv *env, jobject obj, jint size){
   7         jobjectArray result;
   8         int i;
   9         jclass intArrCls=env->FindClass("[I");
  10         if(intArrCls==NULL){
  11                 return NULL;
  12         }
  13         result = env->NewObjectArray(size,intArrCls,NULL);
  14         if(result==NULL){
  15                 return NULL;
  16         }
  17         srand(time(NULL));
  18         
  19         for(i=0;i<size;i++){
  20                 jint tmp[256];
  21                 int j;
  22                 jintArray iarr= env->NewIntArray(size);
  23                 if(iarr==NULL){
  24                         return NULL;
  25                 }
  26                 ;
  27                 for(j=0;j<size;j++){
  28                         
  29                         int randVal=rand() % 10;
  30                         tmp[j]=randVal;
  31                 }
  32                 env->SetIntArrayRegion(iarr,0,size,tmp);
  33                 env->SetObjectArrayElement(result,i,iarr);
  34                 env->DeleteLocalRef(iarr);
  35         }
  36         return result;
  37   }

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