update

Author: yennj12

doc/cheatsheet/java_trick.md

@@ -554,6 +554,13 @@ int[][] intervals = new int[][]{ {15,20}, {0,30}, {5,10} };
 
 
 ### 1-4-3) Sort List VS Array
+
+#### In Summary !!!!
+
+- `Arrays.sort` for array sorting
+- `Collections.sort` for list, HashMap .. sorting
+
+
 ```java
 // java
 // LC 214

leetcode_java/src/main/java/dev/Sorting/ArraySortTest.java

@@ -24,6 +24,55 @@ public void testOnArrayVal1(){
          */
         System.out.println(">>> (before) arr = " + Arrays.asList(arr));
 
+        /**
+         *  Why for hashMap, List we use `Collections.sort`
+         *  but for array, we use `Arrays.sort` ?
+         *
+         *
+         *  -> In brief, `array` is the basic data structure in java,
+         *     it's a fixed size (not dynamic),  `Arrays utility` offers basic
+         *     functions for support operation on such structures
+         *
+         *     while `collections` is the dynamic data structure,
+         *     (e.g. ArrayList, LinkedList, HashMap...)
+         *
+         *
+         *
+         *
+         *  1)
+         *
+         *  - Collections Framework:
+         *
+         *     Java provides the Collections Framework to
+         *     work with dynamic collections that have flexible sizes,
+         *     such as List, Set, and Queue. Since List is part of the framework,
+         *     Collections.sort() is used for sorting List objects.
+         *     The framework provides numerous utilities for adding, removing, and sorting elements.
+         *
+         *  - Arrays:
+         *
+         *     Arrays are a more primitive data structure in Java.
+         *     The Arrays.sort() method is provided by the Arrays utility
+         *     class specifically for sorting arrays, which do not have the flexibility
+         *     of the List interface. Arrays are fixed-size,
+         *     and Arrays.sort() provides an efficient way to sort them.
+         *
+         *
+         *  2)  Key Differences Between Sorting with Arrays.sort() vs Collections.sort():
+         *
+         *     - Arrays.sort():
+         *         Works with primitive arrays (e.g., int[], double[])
+         *         and arrays of objects. It is optimized for the underlying
+         *         fixed-size nature of arrays and is directly implemented in the Arrays class.
+         *
+         *
+         *     - Collections.sort():
+         *        Works only with List types (e.g., ArrayList, LinkedList, etc.).
+         *        It is implemented in the Collections utility class and requires
+         *        that the data be in a List form.
+         *
+         */
+
         /**
          *  NOTE !!!
          *