solution

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

@@ -1,19 +1,97 @@
 package core.basesyntax;
 
 public class MyHashMap<K, V> implements MyMap<K, V> {
+    private static final int DEFAULT_CAPACITY = 16;
+    private static final int MAX_CAPACITY = 1 << 30; // ~1B entries
+    private static final double LOAD_FACTOR = 0.75;
+    private int capacity;
+    private int threshold;
+    private int size;
+    private Node<K, V>[] table;
 
     @Override
     public void put(K key, V value) {
-
+        if (table == null || size >= threshold) {
+            resize();
+        }
+        int index = indexFor(hash(key));
+        Node<K, V> node = table[index];
+        if (node == null) {
+            table[index] = new Node<>(key, value);
+            size++;
+            return;
+        }
+        while (true) {
+            if ((key == null && node.key == null) || (node.key != null && node.key.equals(key))) {
+                node.value = value;
+                return;
+            }
+            if (node.next == null) {
+                node.next = new Node<>(key, value);
+                size++;
+                return;
+            }
+            node = node.next;
+        }
     }
 
     @Override
     public V getValue(K key) {
+        if (table == null) {
+            return null;
+        }
+        int index = indexFor(hash(key));
+        Node<K, V> node = table[index];
+        while (node != null) {
+            if ((key == null && node.key == null) || (node.key != null && node.key.equals(key))) {
+                return node.value;
+            }
+            node = node.next;
+        }
         return null;
     }
 
     @Override
     public int getSize() {
-        return 0;
+        return size;
+    }
+
+    private int hash(K key) {
+        return (key == null) ? 0 : key.hashCode();
+    }
+
+    private int indexFor(int hash) {
+        return hash & (capacity - 1);
+    }
+
+    private void resize() {
+        int newCapacity = (table == null) ? DEFAULT_CAPACITY : capacity * 2;
+        if (newCapacity > MAX_CAPACITY) {
+            newCapacity = MAX_CAPACITY;
+        }
+        capacity = newCapacity;
+        threshold = (int) (capacity * LOAD_FACTOR);
+        size = 0;
+        Node<K, V>[] oldTable = table;
+        table = (Node<K, V>[]) new Node[capacity];
+        if (oldTable != null) {
+            for (Node<K, V> node : oldTable) {
+                while (node != null) {
+                    put(node.key, node.value);
+                    node = node.next;
+                }
+            }
+        }
+    }
+
+    private static class Node<K, V> {
+        private final K key;
+        private V value;
+        private Node<K, V> next;
+
+        private Node(K key, V value) {
+            this.key = key;
+            this.value = value;
+        }
     }
 }