Initial data commit

Task/Call-a-foreign-language-function/Java/call-a-foreign-language-function-1.java

@@ -0,0 +1,12 @@
+public class JNIDemo
+{
+  static
+  {  System.loadLibrary("JNIDemo");  }
+
+  public static void main(String[] args)
+  {
+    System.out.println(callStrdup("Hello World!"));
+  }
+
+  private static native String callStrdup(String s);
+}

Task/Call-a-foreign-language-function/Java/call-a-foreign-language-function-2.java

@@ -0,0 +1,21 @@
+/* DO NOT EDIT THIS FILE - it is machine generated */
+#include <jni.h>
+/* Header for class JNIDemo */
+
+#ifndef _Included_JNIDemo
+#define _Included_JNIDemo
+#ifdef __cplusplus
+extern "C" {
+#endif
+/*
+ * Class:     JNIDemo
+ * Method:    callStrdup
+ * Signature: (Ljava/lang/String;)Ljava/lang/String;
+ */
+JNIEXPORT jstring JNICALL Java_JNIDemo_callStrdup
+  (JNIEnv *, jclass, jstring);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

Task/Call-a-foreign-language-function/Java/call-a-foreign-language-function-3.java

@@ -0,0 +1,43 @@
+#include "string.h"
+#include "JNIDemo.h"
+
+void throwByName(JNIEnv* env, const char* className, const char* msg)
+{
+  jclass exceptionClass = (*env)->FindClass(env, className);
+  if (exceptionClass != NULL)
+  {
+    (*env)->ThrowNew(env, exceptionClass, msg);
+    (*env)->DeleteLocalRef(env, exceptionClass);
+  }
+  return;
+}
+
+JNIEXPORT jstring JNICALL Java_JNIDemo_callStrdup(JNIEnv *env, jclass cls, jstring s)
+{
+  const jbyte* utf8String;
+  char* dupe;
+  jstring dupeString;
+
+  if (s == NULL)
+  {
+    throwByName(env, "java/lang/NullPointerException", "String is null");
+    return NULL;
+  }
+
+  // Convert from UTF-16 to UTF-8 (C-style)
+  utf8String = (*env)->GetStringUTFChars(env, s, NULL);
+
+  // Duplicate
+  dupe = strdup(utf8String);
+
+  // Free the UTF-8 string back to the JVM
+  (*env)->ReleaseStringUTFChars(env, s, utf8String);
+
+  // Convert the duplicate string from strdup to a Java String
+  dupeString = (*env)->NewStringUTF(env, dupe);
+
+  // Free the duplicate c-string back to the C runtime heap
+  free(dupe);
+
+  return dupeString;
+}