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Author: Mmabiaa

Main_Array.java

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+public class Main_Array {
+    public static void main(String[] args) {
+        //Arrays
+        int[] array = {10, 20, 30, 40, 50};
+
+        System.out.println("Element at index 0:" + array[0]);
+        System.out.println("Element at index 2:" + array[2]);
+        System.out.println("Element at index 4:" + array[4]);
+
+        int sum = 0;
+        for(int i = 0; i < array.length; i++){
+            sum =+ array[i];
+        }
+        System.out.println("Sum of Array elements: " + sum);
+
+        array[2] = 35;
+        System.out.println("Updated element at index 2: " + array[2]);
+
+        System.out.println("Element in the Array: " );
+
+        for(int i:array ){
+            System.out.println(i);
+        }
+    }
+}

Main_ArrayList.java

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+import java.util.*;
+
+public class Main_ArrayList{
+
+//Class method for the ArrayList.
+
+
+
+    public static void main(String[] args) {
+       // Create an ArrayList to store integers
+      ArrayList<Integer> arrayList = new ArrayList<Integer>(List.of(10, 20, 30, 40, 50));
+
+      // Output of elements with ref to their index.
+        System.out.println("Element at index 0: " + arrayList.get(0));
+        System.out.println("Element at index 2: " + arrayList.get(2));
+        System.out.println("Element at index 4: " + arrayList.get(4));
+
+        //Sum of all elements in the arraylist
+        int sum = arrayList.stream().mapToInt(Integer::intValue).sum();
+        System.out.println("Sum of ArrayList elements: " + sum);
+
+        arrayList.set(2, 35);
+        System.out.println("Updated element at index 2: " + arrayList.get(2));
+
+        System.out.println("Element in the ArrayList: ");
+        for(int number: arrayList){
+            System.out.println(number);
+        }
+    }
+}

Main_HashMap.java

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+import java.util.*;
+
+public class Main_HashMap {
+    public static void main(String[] args) {
+        HashMap <String, Integer> hashMap = new HashMap<>();
+        //Adding keys to a hash map.
+        hashMap.put("John", 25);
+        hashMap.put("Alice", 30);
+        hashMap.put("Bob", 35);
+
+        //Displaying the integer values.
+        int alice = hashMap.get("Alice");
+        int john = hashMap.get("John");
+        System.out.println("Age of John: " + john);
+        System.err.println("Age of Alice: " + alice);
+
+        //Checking if a key is present.
+        Boolean isPresent = hashMap.containsKey("Bob");
+        System.out.println("Is Bob present? " + isPresent);
+
+        //Printing all key-value pairs.
+        for(String key: hashMap.keySet()){
+            System.out.println(key+":"+hashMap.get(key));
+        }
+
+        //Size of the hash map
+        int Size = hashMap.size();
+        System.out.println("Size of the hash map: "+Size);
+    }
+}

Main_LinkedList.java

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+import java.util.*;
+
+public class Main_LinkedList {
+    public static void main(String[] args) {
+        //LinkedList.
+        LinkedList <Integer> linkedList = new LinkedList<>();
+       //Adding elements to linkedList
+        linkedList.add(10);
+        linkedList.add(20);
+        linkedList.add(30);
+        linkedList.add(40);
+        linkedList.add(50);
+
+        System.out.println("LinkedList:"+ linkedList);
+
+        //Removing first element.
+        linkedList.removeFirst();
+        System.out.println("LinkedList after removing first element:"+linkedList);
+
+        //Checking if an element is in the linked list.
+        Boolean Check = linkedList.contains(30);
+        System.out.println("LinkedList contains element '30'? " + Check);
+
+        int first = linkedList.getFirst();
+        int last = linkedList.getLast();
+
+        System.out.println("First element: " + first);
+        System.out.println("Last element: " + last);
+
+        // Clearing the linked list elements
+        linkedList.clear();
+        System.out.println("LinkedList after clearing: " + linkedList);
+
+    }
+}

Main_Queue.java

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+import java.util.*;
+
+public class Main_Queue {
+    public static void main(String[] args) {
+        Queue <Integer> queue = new LinkedList<Integer>();
+        queue.offer(10);
+        queue.offer(20);
+        queue.offer(30);
+        queue.offer(40);
+        queue.offer(50);
+
+        //Print first element
+        int first = queue.peek();
+        System.out.println("Front element: " + first);
+        
+        //Dequeuing the elements.
+        while(!queue.isEmpty()) {
+            int e = queue.poll();
+            System.out.println("Dequeue element: " + e);
+        }
+    }
+}

Main_Stack.java

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+import java.util.*;
+
+public class Main_Stack {
+    public static void main(String[] args) {
+        Stack<Integer> stack = new Stack<Integer>();
+        
+        //Adding stack elements
+        stack.push(10);
+        stack.push(20);
+        stack.push(30);
+
+        //Viewing the top elements of a STack.
+        int top = stack.peek();
+        System.out.println("Top element: " + top);
+        System.out.println("Popped element: " + stack.pop());
+
+        //Checking if stack is empty.
+        boolean isEmpty = stack.empty();
+        System.out.println("Is stack empty: " + isEmpty);
+
+        //Checking the size
+        int Size = stack.size();
+        System.out.println("Stack size: " +Size);
+        //Printing stack elements.
+        System.out.println("Stack Elements:");
+        for(int e : stack)
+        System.out.println(e); 
+    }
+}