Take out Use System Properties in a Native Executable tab on Guides page

Author: ban-mi

docs/reference-manual/native-image/guides/use-system-properties.md

@@ -3,114 +3,9 @@ layout: ni-docs
 toc_group: how-to-guides
 link_title: Use System Properties
 permalink: /reference-manual/native-image/guides/use-system-properties/
-redirect_to: /reference-manual/native-image/overview/Options/
+redirect_to: https://github.com/graalvm/graalvm-demos/tree/master/native-image/use-system-properties
 ---
 
 # Use System Properties in a Native Executable
 
-Assume you have compiled the following Java application using `javac`:
-```java
-public class App {
-    public static void main(String[] args) {
-        System.getProperties().list(System.out);
-    }
-}
-```
-
-If you build a native executable using `native-image -Dfoo=bar App`, the system property `foo` will **only** be available at build time.
-This means it is available to the [code in your application that is run at build time](http://www.graalvm.org/sdk/javadoc/org/graalvm/nativeimage/ImageInfo.html#inImageBuildtimeCode--) (usually static field initializations and static initializers).
-But if you run the resulting executable, it will not contain `foo` in the printed list of properties.
-
-If, on the other hand, you run the executable with `app -Dfoo=bar`, it will display `foo` in the list of properties because you specified this property.
-
-## Read System Properties at Build Time
-
-You can read system properties at build time and incorporate them into the native executable, as shown in the following example.
-
-### Prerequisite 
-Make sure you have installed a GraalVM JDK.
-The easiest way to get started is with [SDKMAN!](https://sdkman.io/jdks#graal).
-For other installation options, visit the [Downloads section](https://www.graalvm.org/downloads/).
-
-1. Save the following Java code into a file named _ReadProperties.java_:
-    ```java
-    public class ReadProperties {
-        private static final String STATIC_PROPERTY_KEY = "static_key";
-        private static final String INSTANCE_PROPERTY_KEY = "instance_key";
-        private static final String STATIC_PROPERTY;
-        private final String instanceProperty;
-        static {
-            System.out.println("Getting value of static property with key: " + STATIC_PROPERTY_KEY);
-            STATIC_PROPERTY = System.getProperty(STATIC_PROPERTY_KEY);
-        }
-    
-        public ReadProperties() {
-            System.out.println("Getting value of instance property with key: " + INSTANCE_PROPERTY_KEY);
-            instanceProperty = System.getProperty(INSTANCE_PROPERTY_KEY);
-        }
-        
-        public void print() {
-            System.out.println("Value of instance property: " + instanceProperty);
-        } 
-        
-        public static void main(String[] args) {
-            System.out.println("Value of static property: " + STATIC_PROPERTY);
-            ReadProperties rp = new ReadProperties();
-            rp.print();
-        } 
-    }
-    ```
-
-2. Compile the application:
-    ```shell
-    javac ReadProperties.java
-    ```
-
-3. Build the native executable, passing a system property as a command-line option. Then run the native executable, passing a different system property on the command line.
-    ```shell
-    native-image -Dstatic_key=STATIC_VALUE ReadProperties
-    ```
-    ```shell
-    ./readproperties -Dinstance_key=INSTANCE_VALUE
-    ```
-
-    You should see the following output:
-    ```shell
-    Getting value of static property with key: static_key
-    Value of static property: null
-    Getting value of instance property with key: instance_key
-    Value of instance property: INSTANCE_VALUE
-    ```
-
-    This indicates that the class static initializer was not run at build time, but at **run time**.
-
-4. To force the class static initializer to run at build time, use the `--initialize-at-build-time` option, as follows:
-    ```shell
-    native-image --initialize-at-build-time=ReadProperties -Dstatic_key=STATIC_VALUE ReadProperties
-    ```
-    In the output from the `native-image` tool you should see the message like this:
-    ```
-    GraalVM Native Image: Generating 'readproperties' (executable)...
-    ==========================================================================
-    Getting value of static property with key: static_key
-    [1/8] Initializing...                                      (4.0s @ 0.13GB)
-    ...
-    ```
-
-5. Run the executable again, as follows:
-    ```shell
-    ./readproperties -Dinstance_key=INSTANCE_VALUE
-    ```
-
-    This time you should see the following output, confirming that the static initializer was run at **build time**, not at run time.
-
-    ```shell
-    Value of static property: STATIC_VALUE
-    Getting value for instance property key: instance_key
-    Value of instance property: INSTANCE_VALUE
-    ```
-
-### Related Documentation
-
-* [Command-line Options: System Properties](../BuildOptions.md#system-properties)
-* [Specify Class Initialization Explicitly](specify-class-initialization.md)
+This guide has been moved to the [graalvm-demos](https://github.com/graalvm/graalvm-demos/tree/master/native-image/use-system-properties) repository.