fix typo

Author: forax

chapter09-list_and_map.jsh

@@ -174,9 +174,9 @@ System.out.println(group);
 // to count the number of occurrence, use `merge()` that takes a key, a value and the function
 // to call if there is already an existing value to combine them
 var letters = List.of("a", "b", "e", "b");
-var occurenceMap = new HashMap<String, Integer>();
-letters.forEach(letter -> occurenceMap.merge(letter, 1, Integer::sum));
-System.out.println(occurenceMap);
+var occurrenceMap = new HashMap<String, Integer>();
+letters.forEach(letter -> occurrenceMap.merge(letter, 1, Integer::sum));
+System.out.println(occurrenceMap);
 
 
 // ### More on transformations

guide/chapter09-list_and_map.md

@@ -225,9 +225,9 @@ to count the number of occurrence, use `merge()` that takes a key, a value and t
 to call if there is already an existing value to combine them
 ```java
 var letters = List.of("a", "b", "e", "b");
-var occurenceMap = new HashMap<String, Integer>();
-letters.forEach(letter -> occurenceMap.merge(letter, 1, Integer::sum));
-System.out.println(occurenceMap);
+var occurrenceMap = new HashMap<String, Integer>();
+letters.forEach(letter -> occurrenceMap.merge(letter, 1, Integer::sum));
+System.out.println(occurrenceMap);
 ```
 
 

jupyter/chapter09-list_and_map.ipynb

@@ -400,7 +400,7 @@
   "execution_count": null,
   "metadata": {},
   "outputs": [],
-  "source": ["var letters = List.of(\"a\", \"b\", \"e\", \"b\");\n", "var occurenceMap = new HashMap<String, Integer>();\n", "letters.forEach(letter -> occurenceMap.merge(letter, 1, Integer::sum));\n", "System.out.println(occurenceMap);\n"]
+  "source": ["var letters = List.of(\"a\", \"b\", \"e\", \"b\");\n", "var occurrenceMap = new HashMap<String, Integer>();\n", "letters.forEach(letter -> occurrenceMap.merge(letter, 1, Integer::sum));\n", "System.out.println(occurrenceMap);\n"]
 }
 ,
 {