Add support for java examples programs compilation

Signed-off-by: Shine <yll@radxa.com>

examples/CMakeLists.txt

@@ -1,6 +1,12 @@
 add_subdirectory (c)
 add_subdirectory (platform)
 
+if ( (DEFINED ENV{JAVA_HOME_NATIVE}) OR (DEFINED ENV{JAVA_HOME}) )
+  #add_subdirectory (java)
+else ()
+  #message ( WARNING "You haven't configured the Java environment variables yet!")
+endif ()
+
 if (NOT ANDROID_TOOLCHAIN)
   add_subdirectory (c++)
 endif ()

examples/java/CMakeLists.txt

@@ -0,0 +1,36 @@
+if (NOT DEFINED ENV{JAVA_HOME_NATIVE})
+    if (NOT DEFINED ENV{JAVA_HOME})
+        message (FATAL_ERROR "Neither JAVA_HOME nor JAVA_HOME_NATIVE are set")
+    endif()
+    set (JAVA_HOME_NATIVE $ENV{JAVA_HOME})
+    set (JAVAC $ENV{JAVA_HOME}/bin/javac)
+    set (JAR $ENV{JAVA_HOME}/bin/jar)
+else ()
+    set (JAVAC $ENV{JAVA_HOME_NATIVE}/bin/javac)
+    set (JAR $ENV{JAVA_HOME_NATIVE}/bin/jar)
+endif ()
+
+set (Main_Class_Name_list
+        AioA0 BlinkIO BlinkOnboard Bmp85
+        CyclePwm3 Example FTDITest GpioMmapped
+        GpioRead6 HelloEdison I2cCompass Isr
+        SpiMAX7219 SpiMCP4261 UartExample)
+
+foreach (Main_Class_Name ${Main_Class_Name_list})
+    configure_file (
+        ${CMAKE_CURRENT_SOURCE_DIR}/manifest.txt.in
+        ${CMAKE_CURRENT_BINARY_DIR}/${Main_Class_Name}/manifest.txt
+        @ONLY
+    )
+
+    if (EXISTS "${CMAKE_CURRENT_BINARY_DIR}/../../src/java/mraa.jar")
+        set (mraa_jar_path ${CMAKE_CURRENT_BINARY_DIR}/../../src/java/mraa.jar)
+    elseif (EXISTS "/usr/local/lib/java/mraa.jar")
+        set (mraa_jar_path /usr/local/lib/java/mraa.jar)
+    endif()
+
+    add_custom_target (${Main_Class_Name}_jar ALL
+        COMMAND ${JAVAC} -cp ${mraa_jar_path} -d ${CMAKE_CURRENT_BINARY_DIR}/${Main_Class_Name} ${CMAKE_CURRENT_SOURCE_DIR}/${Main_Class_Name}.java
+        COMMAND cd ${CMAKE_CURRENT_BINARY_DIR}/${Main_Class_Name}/ && ${JAR} -cmvf manifest.txt ${Main_Class_Name}.jar ${Main_Class_Name}.class
+    )
+endforeach ()