Merge pull request #713 from yanqingmen/java_wrapper

java wrapper modification

Makefile

@@ -5,7 +5,7 @@ export MPICXX = mpicxx
 export LDFLAGS= -pthread -lm
 export CFLAGS = -Wall -O3 -msse2  -Wno-unknown-pragmas -funroll-loops
 # java include path
-export JAVAINCFLAGS = -I${JAVA_HOME}/include -I${JAVA_HOME}/include/linux -I./java
+export JAVAINCFLAGS = -I${JAVA_HOME}/include -I./java
 
 ifeq ($(OS), Windows_NT)
 	export CXX = g++ -m64
@@ -16,6 +16,11 @@ UNAME= $(shell uname)
 
 ifeq ($(UNAME), Linux)
 	LDFLAGS += -lrt
+	JAVAINCFLAGS += -I${JAVA_HOME}/include/linux
+endif
+
+ifeq ($(UNAME), Darwin)
+	JAVAINCFLAGS += -I${JAVA_HOME}/include/darwin
 endif
 
 ifeq ($(no_omp),1)
@@ -71,7 +76,7 @@ else
 endif
 
 # java lib
-JLIB = java/libxgboostjavawrapper.so
+JLIB = java/libxgboost4j.so
 
 # specify tensor path
 BIN = xgboost
@@ -103,8 +108,8 @@ main.o: src/xgboost_main.cpp src/utils/*.h src/*.h src/learner/*.hpp src/learner
 xgboost:  updater.o gbm.o io.o main.o $(LIBRABIT) $(LIBDMLC)
 wrapper/xgboost_wrapper.dll wrapper/libxgboostwrapper.so: wrapper/xgboost_wrapper.cpp src/utils/*.h src/*.h src/learner/*.hpp src/learner/*.h  updater.o gbm.o io.o $(LIBRABIT) $(LIBDMLC)
 
-java: java/libxgboostjavawrapper.so
-java/libxgboostjavawrapper.so: java/xgboost4j_wrapper.cpp wrapper/xgboost_wrapper.cpp src/utils/*.h src/*.h src/learner/*.hpp src/learner/*.h  updater.o gbm.o io.o $(LIBRABIT) $(LIBDMLC)
+java: java/libxgboost4j.so
+java/libxgboost4j.so: java/xgboost4j_wrapper.cpp wrapper/xgboost_wrapper.cpp src/utils/*.h src/*.h src/learner/*.hpp src/learner/*.h  updater.o gbm.o io.o $(LIBRABIT) $(LIBDMLC)
 
 # dependency on rabit
 subtree/rabit/lib/librabit.a: subtree/rabit/src/engine.cc

java/README.md

@@ -17,12 +17,17 @@ core of this wrapper is two classes:
 
 ## build native library
 
-for windows: open the xgboost.sln in "../windows" folder, you will found the xgboostjavawrapper project, you should do the following steps to build wrapper library:
+for windows: open the xgboost.sln in "../windows" folder, you will found the xgboost4j project, you should do the following steps to build wrapper library:
  * Select x64/win32 and Release in build
- * (if you have setted `JAVA_HOME` properly in windows environment variables, escape this step) right click on xgboostjavawrapper project -> choose "Properties" -> click on "C/C++" in the window -> change the "Additional Include Directories" to fit your jdk install path.
+ * (if you have setted `JAVA_HOME` properly in windows environment variables, escape this step) right click on xgboost4j project -> choose "Properties" -> click on "C/C++" in the window -> change the "Additional Include Directories" to fit your jdk install path.
  * rebuild all
  * double click "create_wrap.bat" to set library to proper place
 
 for linux: 
  * make sure you have installed jdk and `JAVA_HOME` has been setted properly
  * run "create_wrap.sh"
+
+for osx:
+ * make sure you have installed jdk
+ * for single thread xgboost, simply run "create_wrap.sh"
+ * for build with openMP, please refer to [build.md](../doc/build.md) to get openmp supported compiler first, and change the line "dis_omp=1" to "dis_omp=0" in "create_wrap.sh", then run "create_wrap.sh"

java/create_wrap.bat

@@ -1,12 +1,12 @@
 echo "move native library"
-set libsource=..\windows\x64\Release\xgboostjavawrapper.dll
+set libsource=..\windows\x64\Release\xgboost4j.dll
 
 if not exist %libsource% (
 goto end
 )
 
 set libfolder=xgboost4j\src\main\resources\lib
-set libpath=%libfolder%\xgboostjavawrapper.dll
+set libpath=%libfolder%\xgboost4j.dll
 if not exist %libfolder% (mkdir %libfolder%)
 if exist %libpath% (del %libpath%)
 move %libsource% %libfolder%

java/create_wrap.sh

@@ -1,12 +1,22 @@
 #!/usr/bin/env sh
-
 echo "build java wrapper"
 
 # cd to script's directory
 pushd `dirname $0` > /dev/null
 
+#settings according to os
+dl="so"
+dis_omp=0
+
+if [ $(uname) == "Darwin" ]; then
+  export JAVA_HOME=$(/usr/libexec/java_home)
+  dl="dylib"
+  #change this to 0 if your compiler support openmp
+  dis_omp=1
+fi
+
 cd ..
-make java
+make java no_omp=${dis_omp}
 cd java
 echo "move native lib"
 
@@ -15,8 +25,8 @@ if [ ! -d "$libPath" ]; then
   mkdir -p "$libPath"
 fi
 
-rm -f xgboost4j/src/main/resources/lib/libxgboostjavawrapper.so
-mv libxgboostjavawrapper.so xgboost4j/src/main/resources/lib/
+rm -f xgboost4j/src/main/resources/lib/libxgboost4j.${dl}
+mv libxgboost4j.so xgboost4j/src/main/resources/lib/libxgboost4j.${dl}
 
 popd > /dev/null
 echo "complete"

java/xgboost4j/README.md

@@ -1,23 +0,0 @@
-# xgboost4j
-this is a java wrapper for xgboost (https://github.com/dmlc/xgboost)  
-the structure of this wrapper is almost the same as the official python wrapper.
-core of this wrapper is two classes:
-
-* DMatrix： for handling data
-
-* Booster: for train and predict
-
-## usage:
-  
-  simple examples could be found in test package:
-
-  * Simple Train Example: org.dmlc.xgboost4j.TrainExample.java
-  
-  * Simple Predict Example: org.dmlc.xgboost4j.PredictExample.java
-  
-  * Cross Validation Example: org.dmlc.xgboost4j.example.CVExample.java
-  
-## native library:
-  
-  only 64-bit linux/windows is supported now, if you want to build native wrapper library yourself, please refer to 
-  https://github.com/yanqingmen/xgboost-java, and put your native library to the "./src/main/resources/lib" folder and replace the originals. (either "libxgboostjavawrapper.so" for linux or "xgboostjavawrapper.dll" for windows) 

java/xgboost4j/src/main/java/org/dmlc/xgboost4j/Booster.java

@@ -233,7 +233,7 @@ public final class Booster {
      * @param predLeaf
      * @return predict results
      */
-    private synchronized float[][] pred(DMatrix data, boolean outPutMargin, long treeLimit, boolean predLeaf) throws XGBoostError {
+    private synchronized float[][] pred(DMatrix data, boolean outPutMargin, int treeLimit, boolean predLeaf) throws XGBoostError {
         int optionMask = 0;
         if(outPutMargin) {
             optionMask = 1;
@@ -284,7 +284,7 @@ public final class Booster {
      * @return predict result
      * @throws org.dmlc.xgboost4j.util.XGBoostError
      */
-    public float[][] predict(DMatrix data, boolean outPutMargin, long treeLimit) throws XGBoostError {
+    public float[][] predict(DMatrix data, boolean outPutMargin, int treeLimit) throws XGBoostError {
         return pred(data, outPutMargin, treeLimit, false);
     }
     
@@ -299,7 +299,7 @@ public final class Booster {
      * @return predict result
      * @throws org.dmlc.xgboost4j.util.XGBoostError
      */
-    public float[][] predict(DMatrix data , long treeLimit, boolean predLeaf) throws XGBoostError {
+    public float[][] predict(DMatrix data , int treeLimit, boolean predLeaf) throws XGBoostError {
         return pred(data, false, treeLimit, predLeaf);
     }
     

java/xgboost4j/src/main/java/org/dmlc/xgboost4j/util/Initializer.java

@@ -31,7 +31,7 @@ public class Initializer {
     static boolean initialized = false;
     public static final String nativePath = "./lib";
     public static final String nativeResourcePath = "/lib/";
-    public static final String[] libNames = new String[] {"xgboostjavawrapper"};
+    public static final String[] libNames = new String[] {"xgboost4j"};
     
     public static synchronized void InitXgboost() throws IOException {
         if(initialized == false) {

java/xgboost4j/src/main/java/org/dmlc/xgboost4j/wrapper/XgboostJNI.java

@@ -41,10 +41,10 @@ public class XgboostJNI {
   public final static native int XGBoosterUpdateOneIter(long handle, int iter, long dtrain);
   public final static native int XGBoosterBoostOneIter(long handle, long dtrain, float[] grad, float[] hess);
   public final static native int XGBoosterEvalOneIter(long handle, int iter, long[] dmats, String[] evnames, String[] eval_info);
-  public final static native int XGBoosterPredict(long handle, long dmat, int option_mask, long ntree_limit, float[][] predicts);
+  public final static native int XGBoosterPredict(long handle, long dmat, int option_mask, int ntree_limit, float[][] predicts);
   public final static native int XGBoosterLoadModel(long handle, String fname);
   public final static native int XGBoosterSaveModel(long handle, String fname);
   public final static native int XGBoosterLoadModelFromBuffer(long handle, long buf, long len);
   public final static native int XGBoosterGetModelRaw(long handle, String[] out_string);
   public final static native int XGBoosterDumpModel(long handle, String fmap, int with_stats, String[][] out_strings);
-}
+}                                                                             

java/xgboost4j/src/test/java/org/dmlc/xgboost4j/BoosterTest.java

@@ -104,5 +104,39 @@ public class BoosterTest {
         IEvaluation eval = new EvalError();
         //error must be less than 0.1
         TestCase.assertTrue(eval.eval(predicts, testMat)<0.1f);
+        
+        //test dump model
+        
     }
+    
+    /**
+     * test cross valiation
+     * @throws XGBoostError 
+     */
+    @Test
+    public void testCV() throws XGBoostError {
+         //load train mat
+        DMatrix trainMat = new DMatrix("../../demo/data/agaricus.txt.train");
+        
+        //set params
+        Map<String, Object> param= new HashMap<String, Object>() {
+            {
+                put("eta", 1.0);
+                put("max_depth", 3);
+                put("silent", 1);
+                put("nthread", 6);
+                put("objective", "binary:logistic");
+                put("gamma", 1.0);
+                put("eval_metric", "error");
+            }
+        };
+        
+        //do 5-fold cross validation
+        int round = 2;
+        int nfold = 5;
+        //set additional eval_metrics
+        String[] metrics = null;
+        
+        String[] evalHist = Trainer.crossValiation(param.entrySet(), trainMat, round, nfold, metrics, null, null);
+     }
 }

java/xgboost4j_wrapper.cpp

@@ -12,39 +12,34 @@
  limitations under the License.
  */
 
-#include <jni.h>
 #include "../wrapper/xgboost_wrapper.h"
 #include "xgboost4j_wrapper.h"
+#include <cstring>
+
+//helper functions
+//set handle
+void setHandle(JNIEnv *jenv, jlongArray jhandle, void* handle) {
+    long out[1];
+    out[0] = (long) handle;
+    jenv->SetLongArrayRegion(jhandle, 0, 1, (const jlong*) out);
+}
 
 JNIEXPORT jstring JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBGetLastError
   (JNIEnv *jenv, jclass jcls) {
     jstring jresult = 0 ;
-    char* result = 0;
-    result = (char *)XGBGetLastError();
-    if (result) jresult = jenv->NewStringUTF((const char *)result);
+    const char* result = XGBGetLastError();
+    if (result) jresult = jenv->NewStringUTF(result);
     return jresult;
 }
 
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromFile
   (JNIEnv *jenv, jclass jcls, jstring jfname, jint jsilent, jlongArray jout) {
-    jint jresult = 0 ;
-    char *fname = (char *) 0 ;
-    int silent;
-    void* result[1];
-    unsigned long out[1];
-    
-    fname = (char *)jenv->GetStringUTFChars(jfname, 0);
-    
-    silent = (int)jsilent; 
-    jresult = (jint) XGDMatrixCreateFromFile((char const *)fname, silent, result);
-    
-    
-    *(void **)&out[0] = *result;
-
-    if (fname) jenv->ReleaseStringUTFChars(jfname, (const char *)fname);
-    
-    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) out);
-    return jresult;
+    DMatrixHandle result;
+    const char* fname = jenv->GetStringUTFChars(jfname, 0);
+    int ret = XGDMatrixCreateFromFile(fname, jsilent, &result);
+    if (fname) jenv->ReleaseStringUTFChars(jfname, fname);    
+    setHandle(jenv, jout, result);
+    return ret;
 }
 
 /*
@@ -54,28 +49,19 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreat
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromCSR
   (JNIEnv *jenv, jclass jcls, jlongArray jindptr, jintArray jindices, jfloatArray jdata, jlongArray jout) {
-    jint jresult = 0 ;
-    bst_ulong nindptr ;
-    bst_ulong nelem;
-    void *result[1];
-    unsigned long out[1];
-  
+    DMatrixHandle result;
     jlong* indptr = jenv->GetLongArrayElements(jindptr, 0);
     jint* indices = jenv->GetIntArrayElements(jindices, 0);
     jfloat* data = jenv->GetFloatArrayElements(jdata, 0); 
-    nindptr = (bst_ulong)jenv->GetArrayLength(jindptr); 
-    nelem = (bst_ulong)jenv->GetArrayLength(jdata); 
-
-    jresult = (jint) XGDMatrixCreateFromCSR((unsigned long const *)indptr, (unsigned int const *)indices, (float const *)data, nindptr, nelem, result);    
-    *(void **)&out[0] = *result;
-    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) out);
-    
-    //release
+    bst_ulong nindptr = (bst_ulong)jenv->GetArrayLength(jindptr); 
+    bst_ulong nelem = (bst_ulong)jenv->GetArrayLength(jdata); 
+    int ret = (jint) XGDMatrixCreateFromCSR((unsigned long const *)indptr, (unsigned int const *)indices, (float const *)data, nindptr, nelem, &result);    
+    setHandle(jenv, jout, result);
+    //Release
     jenv->ReleaseLongArrayElements(jindptr, indptr, 0);
     jenv->ReleaseIntArrayElements(jindices, indices, 0);
     jenv->ReleaseFloatArrayElements(jdata, data, 0);
-    
-    return jresult;
+    return ret;
 }
 
 /*
@@ -85,28 +71,21 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreat
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromCSC
   (JNIEnv *jenv, jclass jcls, jlongArray jindptr, jintArray jindices, jfloatArray jdata, jlongArray jout) {
-    jint jresult = 0;
-    bst_ulong nindptr ;
-    bst_ulong nelem;
-    void *result[1];
-    unsigned long out[1];
-  
+    DMatrixHandle result;  
     jlong* indptr = jenv->GetLongArrayElements(jindptr, NULL);
     jint* indices = jenv->GetIntArrayElements(jindices, 0);
     jfloat* data = jenv->GetFloatArrayElements(jdata, NULL);
-    nindptr = (bst_ulong)jenv->GetArrayLength(jindptr); 
-    nelem = (bst_ulong)jenv->GetArrayLength(jdata); 
+    bst_ulong nindptr = (bst_ulong)jenv->GetArrayLength(jindptr); 
+    bst_ulong nelem = (bst_ulong)jenv->GetArrayLength(jdata); 
 
-    jresult = (jint) XGDMatrixCreateFromCSC((unsigned long const *)indptr, (unsigned int const *)indices, (float const *)data, nindptr, nelem, result);  
-    *(void **)&out[0] = *result;
-    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) out);
-    
+    int ret = (jint) XGDMatrixCreateFromCSC((unsigned long const *)indptr, (unsigned int const *)indices, (float const *)data, nindptr, nelem, &result);  
+    setHandle(jenv, jout, result);   
     //release
     jenv->ReleaseLongArrayElements(jindptr, indptr, 0);
     jenv->ReleaseIntArrayElements(jindices, indices, 0);
     jenv->ReleaseFloatArrayElements(jdata, data, 0);
     
-    return jresult;
+    return ret;
 }
 
 /*
@@ -116,27 +95,15 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreat
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreateFromMat
   (JNIEnv *jenv, jclass jcls, jfloatArray jdata, jint jnrow, jint jncol, jfloat jmiss, jlongArray jout) {
-    jint jresult = 0 ;
-    bst_ulong nrow ;
-    bst_ulong ncol ;
-    float miss ;
-    void *result[1];
-    unsigned long out[1];
-  
-
+    DMatrixHandle result;
     jfloat* data = jenv->GetFloatArrayElements(jdata, 0);
-    nrow = (bst_ulong)jnrow; 
-    ncol = (bst_ulong)jncol; 
-    miss = (float)jmiss; 
-    
-    jresult = (jint) XGDMatrixCreateFromMat((float const *)data, nrow, ncol, miss, result);
-    *(void **)&out[0] = *result;
-    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) out);
-  
+    bst_ulong nrow = (bst_ulong)jnrow; 
+    bst_ulong ncol = (bst_ulong)jncol; 
+    int ret = (jint) XGDMatrixCreateFromMat((float const *)data, nrow, ncol, jmiss, &result);
+    setHandle(jenv, jout, result);
     //release
     jenv->ReleaseFloatArrayElements(jdata, data, 0);
-  
-    return jresult;
+    return ret;
 }
 
 /*
@@ -146,24 +113,18 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixCreat
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSliceDMatrix
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jintArray jindexset, jlongArray jout) {
-    jint jresult = 0 ;
-    void *handle = (void *) 0 ;
-    bst_ulong len;
-    void *result[1];
-    unsigned long out[1];
+    DMatrixHandle result;
+    DMatrixHandle handle = (DMatrixHandle) jhandle; 
 
     jint* indexset = jenv->GetIntArrayElements(jindexset, 0);
-    handle = *(void **)&jhandle; 
-    len = (bst_ulong)jenv->GetArrayLength(jindexset); 
+    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jindexset); 
 
-    jresult = (jint) XGDMatrixSliceDMatrix(handle, (int const *)indexset, len, result);
-    *(void **)&out[0] = *result;
-    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) out);
-    
+    int ret = XGDMatrixSliceDMatrix(handle, (int const *)indexset, len, &result);
+    setHandle(jenv, jout, result);
     //release
     jenv->ReleaseIntArrayElements(jindexset, indexset, 0);
     
-    return jresult;
+    return ret;
 }
 
 /*
@@ -172,12 +133,10 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSlice
  * Signature: (J)V
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixFree
-  (JNIEnv *jenv, jclass jcls, jlong jhandle) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    handle = *(void **)&jhandle; 
-    jresult = (jint) XGDMatrixFree(handle);
-    return jresult;
+  (JNIEnv *jenv, jclass jcls, jlong jhandle) {    
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
+    int ret = XGDMatrixFree(handle);
+    return ret;
 }
 
 /*
@@ -187,19 +146,11 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixFree
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSaveBinary
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfname, jint jsilent) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *fname = (char *) 0 ;
-    int silent ;
-    handle = *(void **)&jhandle; 
-    fname = 0;
-    fname = (char *)jenv->GetStringUTFChars(jfname, 0);
-
-    silent = (int)jsilent; 
-    jresult = (jint) XGDMatrixSaveBinary(handle, (char const *)fname, silent);
-    if (fname) jenv->ReleaseStringUTFChars(jfname, (const char *)fname);
-    
-    return jresult;
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
+    const char* fname = jenv->GetStringUTFChars(jfname, 0);
+    int ret = XGDMatrixSaveBinary(handle, fname, jsilent);
+    if (fname) jenv->ReleaseStringUTFChars(jfname, (const char *)fname);    
+    return ret;
 }
 
 /*
@@ -209,26 +160,16 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSaveB
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetFloatInfo
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jfloatArray jarray) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *field = (char *) 0 ;
-    bst_ulong len;
-
-
-    handle = *(void **)&jhandle; 
-
-    field = (char *)jenv->GetStringUTFChars(jfield, 0);
-
-    
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
+    const char*  field = jenv->GetStringUTFChars(jfield, 0);
+   
     jfloat* array = jenv->GetFloatArrayElements(jarray, NULL);
-    len = (bst_ulong)jenv->GetArrayLength(jarray); 
-    jresult = (jint) XGDMatrixSetFloatInfo(handle, (char const *)field, (float const *)array, len);
-    
+    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jarray); 
+    int ret = XGDMatrixSetFloatInfo(handle, field, (float const *)array, len);   
     //release
-    if (field) jenv->ReleaseStringUTFChars(jfield, (const char *)field);
-    jenv->ReleaseFloatArrayElements(jarray, array, 0);
-    
-    return jresult;
+    if (field) jenv->ReleaseStringUTFChars(jfield, field);
+    jenv->ReleaseFloatArrayElements(jarray, array, 0);   
+    return ret;
 }
 
 /*
@@ -238,24 +179,16 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetFl
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetUIntInfo
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jintArray jarray) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *field = (char *) 0 ;
-    bst_ulong len ;
-    handle = *(void **)&jhandle; 
-    field = 0;
-    field = (char *)jenv->GetStringUTFChars(jfield, 0);
-
-    
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
+    const char*  field = jenv->GetStringUTFChars(jfield, 0);   
     jint* array = jenv->GetIntArrayElements(jarray, NULL);
-    len = (bst_ulong)jenv->GetArrayLength(jarray);
-
-    jresult = (jint) XGDMatrixSetUIntInfo(handle, (char const *)field, (unsigned int const *)array, len);
+    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jarray);
+    int ret = XGDMatrixSetUIntInfo(handle, (char const *)field, (unsigned int const *)array, len);
     //release
     if (field) jenv->ReleaseStringUTFChars(jfield, (const char *)field);
     jenv->ReleaseIntArrayElements(jarray, array, 0);
     
-    return jresult;
+    return ret;
 }
 
 /*
@@ -265,20 +198,13 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetUI
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetGroup
   (JNIEnv * jenv, jclass jcls, jlong jhandle, jintArray jarray) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    bst_ulong len ;
-
-    handle = *(void **)&jhandle;
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
     jint* array = jenv->GetIntArrayElements(jarray, NULL);
-    len = (bst_ulong)jenv->GetArrayLength(jarray); 
-
-    jresult = (jint) XGDMatrixSetGroup(handle, (unsigned int const *)array, len);
-    
+    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jarray); 
+    int ret = XGDMatrixSetGroup(handle, (unsigned int const *)array, len);    
     //release
-    jenv->ReleaseIntArrayElements(jarray, array, 0);
-    
-    return jresult;
+    jenv->ReleaseIntArrayElements(jarray, array, 0);    
+    return ret;
 }
 
 /*
@@ -288,30 +214,19 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixSetGr
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixGetFloatInfo
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jobjectArray jout) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *field = (char *) 0 ;
-    bst_ulong len[1];
-    *len = 0;
-    float *result[1];
-
-    handle = *(void **)&jhandle; 
-    field = 0;
-    if (jfield) {
-        field = (char *)jenv->GetStringUTFChars(jfield, 0);
-        if (!field) return 0;
-    }
-    
-    jresult = (jint) XGDMatrixGetFloatInfo(handle, (char const *)field, len, (const float **) result);
- 
-    if (field) jenv->ReleaseStringUTFChars(jfield, (const char *)field);
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
+    const char*  field = jenv->GetStringUTFChars(jfield, 0);
+    bst_ulong len;
+    float *result;    
+    int ret = XGDMatrixGetFloatInfo(handle, field, &len, (const float**) &result);
+    if (field) jenv->ReleaseStringUTFChars(jfield, field);
   
-    jsize jlen = (jsize)*len;
+    jsize jlen = (jsize) len;
     jfloatArray jarray = jenv->NewFloatArray(jlen);
-    jenv->SetFloatArrayRegion(jarray, 0, jlen, (jfloat *) *result);
+    jenv->SetFloatArrayRegion(jarray, 0, jlen, (jfloat *) result);
     jenv->SetObjectArrayElement(jout, 0, (jobject) jarray);
     
-    return jresult;
+    return ret;
 }
 
 /*
@@ -321,25 +236,18 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixGetFl
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixGetUIntInfo
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfield, jobjectArray jout) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *field = (char *) 0 ;
-    bst_ulong len[1];
-    *len = 0;
-    unsigned int *result[1];
-
-    handle = *(void **)&jhandle; 
-    field = (char *)jenv->GetStringUTFChars(jfield, 0);
-    
-    jresult = (jint) XGDMatrixGetUIntInfo(handle, (char const *)field, len, (const unsigned int **) result);
- 
-    if (field) jenv->ReleaseStringUTFChars(jfield, (const char *)field);
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
+    const char*  field = jenv->GetStringUTFChars(jfield, 0);
+    bst_ulong len;
+    unsigned int *result;    
+    int ret = (jint) XGDMatrixGetUIntInfo(handle, field, &len, (const unsigned int **) &result);
+    if (field) jenv->ReleaseStringUTFChars(jfield, field);
   
-    jsize jlen = (jsize)*len;
+    jsize jlen = (jsize) len;
     jintArray jarray = jenv->NewIntArray(jlen);
-    jenv->SetIntArrayRegion(jarray, 0, jlen, (jint *) *result);
+    jenv->SetIntArrayRegion(jarray, 0, jlen, (jint *) result);
     jenv->SetObjectArrayElement(jout, 0, jarray);
-    return jresult;
+    return ret;
 }
 
 /*
@@ -349,13 +257,11 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixGetUI
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixNumRow
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jlongArray jout) {
-    jint jresult = 0 ;
-    void *handle = (void *) 0 ;
+    DMatrixHandle handle = (DMatrixHandle) jhandle;
     bst_ulong result[1];
-    handle = *(void **)&jhandle; 
-    jresult = (jint) XGDMatrixNumRow(handle, result);
+    int ret = (jint) XGDMatrixNumRow(handle, result);
     jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) result);
-    return jresult;
+    return ret;
 }
 
 /*
@@ -365,35 +271,30 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGDMatrixNumRo
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterCreate
   (JNIEnv *jenv, jclass jcls, jlongArray jhandles, jlongArray jout) {
-    jint jresult = 0;
-    void **handles = 0;
+    DMatrixHandle* handles;
     bst_ulong len = 0;
-    void *result[1];
     jlong* cjhandles = 0;
-    unsigned long out[1];
+    BoosterHandle result;
     
     if(jhandles) {
         len = (bst_ulong)jenv->GetArrayLength(jhandles);
-        handles = new void*[len];
+        handles = new DMatrixHandle[len];
         //put handle from jhandles to chandles
         cjhandles = jenv->GetLongArrayElements(jhandles, 0);
         for(bst_ulong i=0; i<len; i++) {
-            handles[i] = *(void **)&cjhandles[i];
+            handles[i] = (DMatrixHandle) cjhandles[i];
         }
     }
     
-    jresult = (jint) XGBoosterCreate(handles, len, result);
-    
+    int ret = XGBoosterCreate(handles, len, &result);    
     //release
     if(jhandles) {
         delete[] handles;
         jenv->ReleaseLongArrayElements(jhandles, cjhandles, 0);
     }
+    setHandle(jenv, jout, result);
     
-    *(void **)&out[0] = *result; 
-    jenv->SetLongArrayRegion(jout, 0, 1, (const jlong *) out);
-    
-    return jresult;
+    return ret;
 }
 
 /*
@@ -403,9 +304,8 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterCreat
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterFree
   (JNIEnv *jenv, jclass jcls, jlong jhandle) {
-    void *handle = (void *) 0 ;
-    handle = *(void **)&jhandle; 
-    return (jint) XGBoosterFree(handle);
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    return XGBoosterFree(handle);
 }
 
 
@@ -416,20 +316,14 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterFree
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterSetParam
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jname, jstring jvalue) {
-    jint jresult = -1;
-    void *handle = (void *) 0 ;
-    char *name = (char *) 0 ;
-    char *value = (char *) 0 ;
-    handle = *(void **)&jhandle; 
-    
-    name = (char *)jenv->GetStringUTFChars(jname, 0);
-    value = (char *)jenv->GetStringUTFChars(jvalue, 0);
-
-    jresult = (jint) XGBoosterSetParam(handle, (char const *)name, (char const *)value);
-    if (name) jenv->ReleaseStringUTFChars(jname, (const char *)name);
-    if (value) jenv->ReleaseStringUTFChars(jvalue, (const char *)value);
-    
-    return jresult;
+    BoosterHandle handle = (BoosterHandle) jhandle;    
+    const char* name = jenv->GetStringUTFChars(jname, 0);
+    const char* value = jenv->GetStringUTFChars(jvalue, 0);
+    int ret = XGBoosterSetParam(handle, name, value);
+    //release
+    if (name) jenv->ReleaseStringUTFChars(jname, name);
+    if (value) jenv->ReleaseStringUTFChars(jvalue, value);    
+    return ret;
 }
 
 /*
@@ -439,13 +333,9 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterSetPa
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterUpdateOneIter
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jint jiter, jlong jdtrain) {
-    void *handle = (void *) 0 ;
-    int iter ;
-    void *dtrain = (void *) 0 ;
-    handle = *(void **)&jhandle; 
-    iter = (int)jiter; 
-    dtrain = *(void **)&jdtrain; 
-    return (jint) XGBoosterUpdateOneIter(handle, iter, dtrain);
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    DMatrixHandle dtrain = (DMatrixHandle) jdtrain;
+    return XGBoosterUpdateOneIter(handle, jiter, dtrain);
 }
 
 /*
@@ -455,23 +345,16 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterUpdat
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterBoostOneIter
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jdtrain, jfloatArray jgrad, jfloatArray jhess) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    void *dtrain = (void *) 0 ;
-    bst_ulong len ;
-
-    handle = *(void **)&jhandle; 
-    dtrain = *(void **)&jdtrain;    
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    DMatrixHandle dtrain = (DMatrixHandle) jdtrain;
     jfloat* grad = jenv->GetFloatArrayElements(jgrad, 0);
     jfloat* hess = jenv->GetFloatArrayElements(jhess, 0);
-    len = (bst_ulong)jenv->GetArrayLength(jgrad);
-    jresult = (jint) XGBoosterBoostOneIter(handle, dtrain, grad, hess, len);
-    
+    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jgrad);
+    int ret = XGBoosterBoostOneIter(handle, dtrain, grad, hess, len);    
     //release
     jenv->ReleaseFloatArrayElements(jgrad, grad, 0);
-    jenv->ReleaseFloatArrayElements(jhess, hess, 0);
-    
-    return jresult;
+    jenv->ReleaseFloatArrayElements(jhess, hess, 0);    
+    return ret;
 }
 
 /*
@@ -481,54 +364,45 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterBoost
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterEvalOneIter
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jint jiter, jlongArray jdmats, jobjectArray jevnames, jobjectArray jout) {
-    jint jresult = 0 ;
-    void *handle = (void *) 0 ;
-    int iter ;
-    void **dmats = 0;
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    DMatrixHandle* dmats = 0;
     char **evnames = 0;
-    bst_ulong len ;
-    char *result[1];
-    
-    handle = *(void **)&jhandle; 
-    iter = (int)jiter; 
-    len = (bst_ulong)jenv->GetArrayLength(jdmats); 
-    
-    
+    char *result = 0;
+    bst_ulong len = (bst_ulong)jenv->GetArrayLength(jdmats);     
     if(len > 0) {
-        dmats = new void*[len];
+        dmats = new DMatrixHandle[len];
         evnames = new char*[len];
     }
-    
     //put handle from jhandles to chandles
     jlong* cjdmats = jenv->GetLongArrayElements(jdmats, 0);
     for(bst_ulong i=0; i<len; i++) {
-        dmats[i] = *(void **)&cjdmats[i];
+        dmats[i] = (DMatrixHandle) cjdmats[i];
     }
-    
-    //transfer jObjectArray to char**
+    //transfer jObjectArray to char**, user strcpy and release JNI char* inplace
     for(bst_ulong i=0; i<len; i++) {
         jstring jevname = (jstring)jenv->GetObjectArrayElement(jevnames, i);
-        evnames[i] = (char *)jenv->GetStringUTFChars(jevname, 0);
+        const char* cevname = jenv->GetStringUTFChars(jevname, 0);
+        evnames[i] = new char[jenv->GetStringLength(jevname)];
+        strcpy(evnames[i], cevname);
+        jenv->ReleaseStringUTFChars(jevname, cevname);
     }
     
-    jresult = (jint) XGBoosterEvalOneIter(handle, iter, dmats, (char const *(*))evnames, len, (const char **) result);
-    
+    int ret = XGBoosterEvalOneIter(handle, jiter, dmats, (char const *(*)) evnames, len, (const char **) &result);    
     if(len > 0) {
         delete[] dmats;
         //release string chars
         for(bst_ulong i=0; i<len; i++) {
-            jstring jevname = (jstring)jenv->GetObjectArrayElement(jevnames, i);
-            jenv->ReleaseStringUTFChars(jevname, (const char*)evnames[i]);
+            delete[] evnames[i];
         }        
         delete[] evnames;
         jenv->ReleaseLongArrayElements(jdmats, cjdmats, 0);
     }
     
     jstring jinfo = 0;
-    if (*result) jinfo = jenv->NewStringUTF((const char *) *result);
+    if (result) jinfo = jenv->NewStringUTF((const char *) result);
     jenv->SetObjectArrayElement(jout, 0, jinfo);
   
-    return jresult;
+    return ret;
 }
 
 /*
@@ -537,29 +411,18 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterEvalO
  * Signature: (JJIJ)[F
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterPredict
-  (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jdmat, jint joption_mask, jlong jntree_limit, jobjectArray jout) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    void *dmat = (void *) 0 ;
-    int option_mask ;
-    unsigned int ntree_limit ;
-    bst_ulong len[1];
-    *len = 0;
-    float *result[1];
+  (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jdmat, jint joption_mask, jint jntree_limit, jobjectArray jout) {
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    DMatrixHandle dmat = (DMatrixHandle) jdmat;
+    bst_ulong len;
+    float *result;
+    int ret = XGBoosterPredict(handle, dmat, joption_mask, (unsigned int) jntree_limit, &len, (const float **) &result);
     
-    handle = *(void **)&jhandle; 
-    dmat = *(void **)&jdmat; 
-    option_mask = (int)joption_mask; 
-    ntree_limit = (unsigned int)jntree_limit; 
-
-    jresult = (jint) XGBoosterPredict(handle, dmat, option_mask, ntree_limit, len, (const float **) result);
-    
-    jsize jlen = (jsize)*len;
+    jsize jlen = (jsize) len;
     jfloatArray jarray = jenv->NewFloatArray(jlen);
-    jenv->SetFloatArrayRegion(jarray, 0, jlen, (jfloat *) *result);
-    jenv->SetObjectArrayElement(jout, 0, jarray);
-    
-    return jresult;
+    jenv->SetFloatArrayRegion(jarray, 0, jlen, (jfloat *) result);
+    jenv->SetObjectArrayElement(jout, 0, jarray);    
+    return ret;
 }
 
 /*
@@ -569,18 +432,12 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterPredi
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterLoadModel
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfname) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *fname = (char *) 0 ;
-    handle = *(void **)&jhandle; 
-    
-    fname = (char *)jenv->GetStringUTFChars(jfname, 0);
-
-    
-    jresult = (jint) XGBoosterLoadModel(handle,(char const *)fname);
-    if (fname) jenv->ReleaseStringUTFChars(jfname, (const char *)fname);
-    
-    return jresult;
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    const char* fname = jenv->GetStringUTFChars(jfname, 0);
+  
+    int ret = XGBoosterLoadModel(handle, fname);
+    if (fname) jenv->ReleaseStringUTFChars(jfname,fname);
+    return ret;
 }
 
 /*
@@ -590,17 +447,13 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterLoadM
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterSaveModel
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfname) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *fname = (char *) 0 ;
-    handle = *(void **)&jhandle; 
-    fname = 0;
-    fname = (char *)jenv->GetStringUTFChars(jfname, 0);
-
-    jresult = (jint) XGBoosterSaveModel(handle, (char const *)fname);
-    if (fname) jenv->ReleaseStringUTFChars(jfname, (const char *)fname);
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    const char*  fname = jenv->GetStringUTFChars(jfname, 0);
     
-    return jresult;
+    int ret = XGBoosterSaveModel(handle, fname);
+    if (fname) jenv->ReleaseStringUTFChars(jfname, fname);
+    
+    return ret;
 }
 
 /*
@@ -610,13 +463,9 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterSaveM
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterLoadModelFromBuffer
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jlong jbuf, jlong jlen) {
-    void *handle = (void *) 0 ;
-    void *buf = (void *) 0 ;
-    bst_ulong len ;
-    handle = *(void **)&jhandle; 
-    buf = *(void **)&jbuf; 
-    len = (bst_ulong)jlen; 
-    return (jint) XGBoosterLoadModelFromBuffer(handle, (void const *)buf, len);
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    void *buf = (void*) jbuf;
+    return XGBoosterLoadModelFromBuffer(handle, (void const *)buf, (bst_ulong) jlen);
 }
 
 /*
@@ -626,20 +475,16 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterLoadM
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterGetModelRaw
   (JNIEnv * jenv, jclass jcls, jlong jhandle, jobjectArray jout) {
-    jint jresult = 0 ;
-    jstring jinfo = 0;
-    void *handle = (void *) 0 ;
-    bst_ulong len[1];
-    *len = 0;
-    char *result[1];
-    handle = *(void **)&jhandle; 
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    bst_ulong len = 0;
+    char *result;
 
-    jresult = (jint)XGBoosterGetModelRaw(handle, len, (const char **) result);
-    if (*result){
-        jinfo = jenv->NewStringUTF((const char *) *result);
+    int ret = XGBoosterGetModelRaw(handle, &len, (const char **) &result);
+    if (result){
+        jstring jinfo = jenv->NewStringUTF((const char *) result);
         jenv->SetObjectArrayElement(jout, 0, jinfo);
     }
-    return jresult;
+    return ret;
 }
 
 /*
@@ -649,32 +494,20 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterGetMo
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterDumpModel
   (JNIEnv *jenv, jclass jcls, jlong jhandle, jstring jfmap, jint jwith_stats, jobjectArray jout) {
-    jint jresult = 0;
-    void *handle = (void *) 0 ;
-    char *fmap = (char *) 0 ;
-    int with_stats ;
-    bst_ulong len[1];
-    *len = 0;
+    BoosterHandle handle = (BoosterHandle) jhandle;
+    const char *fmap = jenv->GetStringUTFChars(jfmap, 0);
+    bst_ulong len = 0; 
+    char **result;
     
-    char **result[1];
-    handle = *(void **)&jhandle; 
-    fmap = 0;
-    if (jfmap) {
-        fmap = (char *)jenv->GetStringUTFChars(jfmap, 0);
-        if (!fmap) return 0;
-    }
-    with_stats = (int)jwith_stats;
-
-    jresult = (jint) XGBoosterDumpModel(handle, (const char *)fmap, with_stats, len, (const char ***) result);
+    int ret = XGBoosterDumpModel(handle, fmap, jwith_stats, &len, (const char ***) &result);
     
-    jsize jlen = (jsize)*len;
+    jsize jlen = (jsize) len;
     jobjectArray jinfos = jenv->NewObjectArray(jlen, jenv->FindClass("java/lang/String"), jenv->NewStringUTF(""));
     for(int i=0 ; i<jlen; i++) {
-        jenv->SetObjectArrayElement(jinfos, i, jenv->NewStringUTF((const char*) result[0][i]));
+        jenv->SetObjectArrayElement(jinfos, i, jenv->NewStringUTF((const char*) result[i]));
     }
     jenv->SetObjectArrayElement(jout, 0, jinfos);
     
-    if (fmap) jenv->ReleaseStringUTFChars(jfmap, (const char *)fmap);
-    
-    return jresult;
+    if (fmap) jenv->ReleaseStringUTFChars(jfmap, (const char *)fmap);   
+    return ret;
 }

java/xgboost4j_wrapper.h

@@ -173,7 +173,7 @@ JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterEvalO
  * Signature: (JJIJ[[F)I
  */
 JNIEXPORT jint JNICALL Java_org_dmlc_xgboost4j_wrapper_XgboostJNI_XGBoosterPredict
-  (JNIEnv *, jclass, jlong, jlong, jint, jlong, jobjectArray);
+  (JNIEnv *, jclass, jlong, jlong, jint, jint, jobjectArray);
 
 /*
  * Class:     org_dmlc_xgboost4j_wrapper_XgboostJNI

windows/xgboost4j/xgboost4j.vcxproj

@@ -30,6 +30,7 @@
   <PropertyGroup Label="Globals">
     <ProjectGuid>{20A0E4D7-20C7-4EC1-BDF6-0D469CE239AA}</ProjectGuid>
     <RootNamespace>xgboost_wrapper</RootNamespace>
+    <ProjectName>xgboost4j</ProjectName>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">