GP-119 update after review

* add missing tests
* update javadoc
* add README.MD

Author: tboychuk

1-0-java-basics/1-3-1-crazy-generics/README.MD

@@ -0,0 +1,28 @@
+# <img src="https://raw.githubusercontent.com/bobocode-projects/resources/master/image/logo_transparent_background.png" height=50/>Crazy Generics
+#### Learn tricky nuances and become the master of type parametrization in Java 💪
+
+### WHY ❓
+Generics in Java provide **safe type parametrization.** Sou can write the logic of a method or a whole class and 
+**reuse it for different types**. Before Java 5 (when generics were introduced), common logic could be reused as well. 
+However, it required **using `Object` everywhere and casting it everytime you want to get an actual type**.
+It **could easily cause `ClassCastException` at runtime which is not safe.**  When using generics, it's still the same `Object`,
+but **now compiler creates casts for you implicitly, and makes sure you didn't mess up with types**, which **moves errors from
+runtime to compile time and makes type parametrization safer.**
+
+### Objectives
+* create a generic class with **simple type parameter** ✅
+* create a generic class with **bounded type parameter** ✅
+* create a generic class with **multiples type parameter** ✅
+* create a generic class with **recursively bounded type parameter** ✅
+* create a **generic method** ✅
+* create a method that accepts a generic class on any type using **wildcard** ✅
+* create method parameter using **bounded wildcard** ✅
+
+### Related materials ℹ️
+* [Effective Java, Chapter 5 – Generics](https://read.amazon.com/kp/embed?asin=B078H61SCH&preview=newtab&linkCode=kpe&ref_=cm_sw_r_kb_dp_SADNB2C41TWARGY4QGKZ) 📘
+
+
+---
+#### 🆕 First time here? – [See Introduction](https://github.com/bobocode-projects/java-fundamentals-course/tree/main/0-0-intro#introduction)
+#### ➡️ Have any feedback? – [Please fill the form ](https://forms.gle/UADe1YKHiFVXQJLF8)
+

1-0-java-basics/1-3-1-crazy-generics/src/main/java/com/bobocode/basics/CrazyGenerics.java

@@ -65,10 +65,10 @@ public interface Converter { // todo: introduce type parameters
      *
      * @param <T> – value type
      */
-    public static class MaxHolder { // todo: refactor class to make it generic
-        private Object max;
+    public static class MaxHolder<T extends Comparable<T>> { // todo: refactor class to make it generic
+        private T max;
 
-        public MaxHolder(Object max) {
+        public MaxHolder(T max) {
             this.max = max;
         }
 
@@ -77,11 +77,13 @@ public MaxHolder(Object max) {
          *
          * @param val a new value
          */
-        public void put(Object val) {
-            throw new ExerciseNotCompletedException(); // todo: update parameter and implement the method
+        public void put(T val) {
+            if (val.compareTo(max) > 0) {
+                max = val;
+            }
         }
 
-        public Object getMax() {
+        public T getMax() {
             return max;
         }
     }
@@ -160,8 +162,9 @@ public static boolean hasNewEntities(Collection<BaseEntity> entities) {
         }
 
         /**
-         * Util method that checks if a provided collection of entities is valid. A validation criteria can be different
-         * for different cases, so it is passed as second parameter.
+         * Util method that checks if a provided collection of entities is valid. An entity is any subclass of
+         * a {@link BaseEntity} A validation criteria can be different for different cases, so it is passed
+         * as second parameter.
          *
          * @param entities            provided collection of entities
          * @param validationPredicate criteria for validation