update readme

README.md

@@ -135,6 +135,25 @@ dotenv["HOME"]
 dotenv["MY_ENV_VAR1"] ?: "default value"
 ```
 
+### Iterate over environment variables
+
+With **Java**
+
+```java
+Iterator<Map.Entry<String,String>> iter = dotenv.iterator();
+while (iter.hasNext()) {
+ System.out.println(iter.next())
+}
+```
+
+or with **Kotlin**
+
+```kotlin
+for (e in dotenv) {
+ print(e)
+}
+```
+
 ## Configuration options
 
 ### *optional* `directory`