did all required tasks

src/main/java/core/basesyntax/MyHashMap.java

@@ -2,18 +2,87 @@
 
 public class MyHashMap<K, V> implements MyMap<K, V> {
 
+    private static final int DEFAULT_CAPACITY = 16;
+    private static final float DEFAULT_LOAD_FACTOR = 0.75f;
+    private static final int CAPACITY_MULTIPLIER = 2;
+    private Node<K, V>[] table;
+    private int size;
+    private int threshold;
+    private final float loadFactor;
+
+    public MyHashMap() {
+        this.loadFactor = DEFAULT_LOAD_FACTOR;
+        this.table = new Node[DEFAULT_CAPACITY];
+        this.threshold = (int) (DEFAULT_CAPACITY * loadFactor);
+    }
+
     @Override
     public void put(K key, V value) {
-
+        if (size >= threshold) {
+            resize();
+        }
+        int index = getIndex(key);
+        Node<K, V> node = table[index];
+        for (Node<K, V> curr = node; curr != null; curr = curr.next) {
+            if (key == curr.key || (key != null && key.equals(curr.key))) {
+                curr.value = value;
+                return;
+            }
+        }
+        table[index] = new Node<>(key, value, node);
+        size++;
     }
 
     @Override
     public V getValue(K key) {
+        int index = getIndex(key);
+        for (Node<K, V> curr = table[index]; curr != null; curr = curr.next) {
+            if (key == curr.key || (key != null && key.equals(curr.key))) {
+                return curr.value;
+            }
+        }
         return null;
     }
 
     @Override
     public int getSize() {
-        return 0;
+        return size;
+    }
+
+    private void resize() {
+        Node<K, V>[] oldTable = table;
+        int newCapacity = oldTable.length * CAPACITY_MULTIPLIER;
+        table = new Node[newCapacity];
+        threshold = (int) (newCapacity * loadFactor);
+        size = 0;
+
+        for (Node<K, V> headNode : oldTable) {
+            Node<K, V> curr = headNode;
+            while (curr != null) {
+                put(curr.key, curr.value);
+                curr = curr.next;
+            }
+        }
     }
+
+    private int getIndex(K key) {
+        if (key == null) {
+            return 0;
+        }
+        return Math.abs(key.hashCode()) % table.length;
+    }
+
+    private static class Node<K, V> {
+        private final K key;
+        private V value;
+        private Node<K, V> next;
+
+        Node(K key, V value, Node<K, V> next) {
+            this.key = key;
+            this.value = value;
+            this.next = next;
+        }
+    }
+
+
 }