For JDK6 you can download the source from java.net. For java.lang the story begins at j2se/src/share/native/java/lang/, and then search… JDK7 rearranges the directory structure a little. Some methods, such as Object.hashCode, may be implemented by hotspot instead or in addition to through JNI/Java. JDK6 is freely licensed through the Java Research License (JRL) and Java … Read more
You need to put dll in your library path (recommended ) before you try to load it. so that you will have to extract it from jar and copy it into lib path . private void loadLib(String path, String name) { name = System.mapLibraryName(name); // extends name with .dll, .so or .dylib InputStream inputStream = … Read more
First, it’s worth noting that by “slow,” we’re talking about something that can take tens of nanoseconds. For trivial native methods, in 2010 I measured calls at an average 40 ns on my Windows desktop, and 11 ns on my Mac desktop. Unless you’re making many calls, you’re not going to notice. That said, calling … Read more
If you’ve examined the documentation and still have questions that should be part of your initial question. In this case, the JNI function in the example creates a number of arrays. The outer array is comprised of an ‘Object’ array creating with the JNI function NewObjectArray(). From the perspective of JNI, that’s all a two … Read more
It is possible to create a single JAR file with all dependencies including the native JNI libraries for one or more platforms. The basic mechanism is to use System.load(File) to load the library instead of the typical System.loadLibrary(String) which searches the java.library.path system property. This method makes installation much simpler as the user does not … Read more
NOTE: this is a bit old code. for the most updated one, check out the project page on github. jni/Android.mk LOCAL_PATH := $(call my-dir) #bitmap operations module include $(CLEAR_VARS) LOCAL_MODULE := JniBitmapOperations LOCAL_SRC_FILES := JniBitmapOperations.cpp LOCAL_LDLIBS := -llog LOCAL_LDFLAGS += -ljnigraphics include $(BUILD_SHARED_LIBRARY) APP_OPTIM := debug LOCAL_CFLAGS := -g #if you need to add more … Read more
In order for System.loadLibrary() to work, the library (on Windows, a DLL) must be in a directory somewhere on your PATH or on a path listed in the java.library.path system property (so you can launch Java like java -Djava.library.path=/path/to/dir). Additionally, for loadLibrary(), you specify the base name of the library, without the .dll at the … Read more
I’m pretty sure the classpath and the shared library search path have little to do with each other. According to The JNI Book (which admittedly is old), on Windows if you do not use the java.library.path system property, the DLL needs to be in the current working directory or in a directory listed in the … Read more
Minimal runnable example Main.java public class Main { public native int square(int i); public static void main(String[] args) { System.loadLibrary(“Main”); System.out.println(new Main().square(2)); } } Main.c #include <jni.h> #include “Main.h” JNIEXPORT jint JNICALL Java_Main_square( JNIEnv *env, jobject obj, jint i) { return i * i; } Compile and run: sudo apt-get install build-essential openjdk-7-jdk export JAVA_HOME=’/usr/lib/jvm/java-7-openjdk-amd64′ … Read more
From the Java language spec: It is a compile time error to import a type from the unnamed package. You’ll have to access the class via reflection or some other indirect method.