Mesheik's Branch For Java Collections

README.md

@@ -1,4 +1,4 @@
-# java-collections
+ # java-collections
 # Java Collections Framework Learning Guide
 
 This repository is designed to help you learn the **Java Collections Framework step-by-step**. Each section introduces a new concept, provides examples, and gives you practice problems to reinforce what you learned.

src/main/java/Collections/Practice/CollectionBasics.java

@@ -2,6 +2,7 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashSet;
 
 public class CollectionBasics {
     public static void main(String[] args) {
@@ -19,6 +20,8 @@ public static void main(String[] args) {
         System.out.println("Count of even numbers: " + countEven(numbers));
         System.out.println("Largest number: " + findMax(numbers));
         System.out.println("Contains duplicates? " + hasDuplicates(numbers));
+        System.out.println("Count occurrences of 20 " + countOccurrences(numbers,20));
+        System.out.println("Numbers greater than 20: " + filterGreaterThanTwenty(numbers));
     }
 
 
@@ -31,8 +34,9 @@ public static int sum(Collection<Integer> numbers) {
         int total = 0;
 
         // TODO:
-        // Loop through the collection
-        // Add each number to total
+        for(int num : numbers){
+            total+= num;
+        }
 
         return total;
     }
@@ -47,8 +51,11 @@ public static int countEven(Collection<Integer> numbers) {
         int count = 0;
 
         // TODO:
-        // Loop through the collection
-        // If the number is even, increase count
+        for(int num : numbers){
+           if (num % 2 ==0){
+               count++;
+           }
+        }
 
         return count;
     }
@@ -63,8 +70,11 @@ public static int findMax(Collection<Integer> numbers) {
         int max = Integer.MIN_VALUE;
 
         // TODO:
-        // Loop through numbers
-        // Update max if current number is larger
+        for (int num : numbers){
+            if(num > max) {
+                max = num;
+            }
+        }
 
         return max;
     }
@@ -78,10 +88,9 @@ public static int findMax(Collection<Integer> numbers) {
     public static boolean hasDuplicates(Collection<Integer> numbers) {
 
         // TODO:
-        // Hint:
-        // Compare the size of a collection with the size of a Set
+        HashSet<Integer> set = new HashSet<>(numbers);
 
-        return false;
+        return set.size() != numbers.size();
     }
 
 
@@ -94,8 +103,12 @@ public static int countOccurrences(Collection<Integer> numbers, int target) {
         int count = 0;
 
         // TODO:
-        // Loop through numbers
-        // If number equals target, increase count
+        for (int num : numbers){
+
+            if (num == target ){
+                count++;
+            }
+        }
 
         return count;
     }
@@ -111,8 +124,11 @@ public static Collection<Integer> filterGreaterThanTwenty(Collection<Integer> nu
         Collection<Integer> result = new ArrayList<>();
 
         // TODO:
-        // Loop through numbers
-        // Add numbers greater than 20 to result
+        for (int num : numbers){
+            if (num >20){
+                result.add(num);
+            }
+        }
 
         return result;
     }

src/main/java/Collections/Practice/CommonMethodsDemo.java

@@ -125,37 +125,38 @@ public static void main(String[] args) {
         // TODO Exploration Section
         // ------------------------------
 
-        /*
-         TODO 1:
-         Create a new Collection called numbers
-         Add the following values:
-         10, 20, 30, 40, 50
-        */
 
+         //TODO 1:
+         Collection<Integer> numbers = new ArrayList<>();
 
-        /*
-         TODO 2:
-         Print the size of the numbers collection
-        */
+        numbers.add(10);
+        numbers.add(20);
+        numbers.add(30);
+        numbers.add(40);
+        numbers.add(50);
 
 
-        /*
-         TODO 3:
-         Check if the collection contains 30
-        */
+         //TODO 2:
+        System.out.println(numbers.size());
 
 
-        /*
-         TODO 4:
-         Remove the number 20
-        */
+         //TODO 3:
+        System.out.println(numbers.contains(30));
 
 
-        /*
-         TODO 5:
-         Loop through the numbers collection
-         and print each value
-        */
+
+
+         //TODO 4:
+        numbers.remove(20);
+        System.out.println(numbers);
+
+
+
+        // TODO 5:
+
+        for(int num : numbers){
+            System.out.println(num);
+        }
 
 
         /*

src/main/java/Collections/Quiz/KnowledgeCheck.md

@@ -17,6 +17,8 @@ B. `Collection` extends `List`
 C. `Collection` is the root interface for most collection types  
 D. `Collection` only stores key-value pairs  
 
+AW: C
+
 ---
 
 ## Question 2
@@ -37,6 +39,8 @@ B. 1
 C. 3
 D. 30
 
+AW: C
+
 ---
 
 ## Question 3
@@ -48,6 +52,8 @@ B. `exists()`
 C. `contains()`
 D. `check()`
 
+AW:C
+
 ---
 
 ## Question 4
@@ -70,6 +76,8 @@ B. `[Jordan]`
 C. `[Alex]`
 D. `[]`
 
+AW: B
+
 ---
 
 ## Question 5
@@ -81,6 +89,8 @@ B. `addAll()`
 C. `insertAll()`
 D. `merge()`
 
+AW:B
+
 ---
 
 ## Question 6
@@ -98,6 +108,8 @@ B. `false`
 C. `0`
 D. Compilation error
 
+AW:A
+
 ---
 
 ## Question 7
@@ -109,6 +121,8 @@ B. `deleteAll()`
 C. `clear()`
 D. `reset()`
 
+AW:A
+
 ---
 
 ## Question 8
@@ -132,6 +146,8 @@ B. `15 10 5`
 C. `0 1 2`
 D. Compilation error
 
+AW:A
+
 ---
 
 ## Question 9
@@ -143,6 +159,8 @@ B. Elements can be removed
 C. Indexed access using `.get(index)`
 D. Elements can be iterated using a loop
 
+AW:C
+
 ---
 
 ## Question 10
@@ -158,5 +176,7 @@ B. It prevents duplicates
 C. It allows flexibility to change implementations later
 D. It forces the collection to be synchronized
 
+AW:C
+
 ```
 ```

src/main/java/Collections/README.md

@@ -1,4 +1,4 @@
-```markdown
+ ```markdown
 # Collection
 
 ## What Is Collection?