Add my hash map

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

@@ -1,19 +1,101 @@
 package core.basesyntax;
 
+import java.util.Objects;
+
 public class MyHashMap<K, V> implements MyMap<K, V> {
+    private static final int DEFAULT_CAPACITY = 16;
+    private static final double DEFAULT_LOAD_FACTOR = .75;
+
+    private int size;
+    private int capacity = DEFAULT_CAPACITY;
+    private Entry<K, V>[] table = new Entry[capacity];
+
+    public MyHashMap() {
+    }
+
+    private static class Entry<K, V> {
+        private final K key;
+        private final int hash;
+        private V value;
+        private Entry<K, V> next;
+
+        public Entry(K key, V value) {
+            this.key = key;
+            this.hash = getHash(key);
+            this.value = value;
+        }
+    }
 
     @Override
     public void put(K key, V value) {
+        if (size + 1 > capacity * DEFAULT_LOAD_FACTOR) {
+            increaseBuckets();
+        }
 
+        int keyHash = getHash(key);
+        int bucketIndex = keyHash & (capacity - 1);
+
+        putInBucket(key, value, keyHash, bucketIndex);
     }
 
     @Override
     public V getValue(K key) {
-        return null;
+        int keyHash = getHash(key);
+        int bucketIndex = keyHash & (capacity - 1);
+        Entry<K, V> entry = table[bucketIndex];
+        if (entry == null) {
+            return null;
+        }
+
+        while (entry != null && (entry.hash != keyHash || !Objects.equals(entry.key, key))) {
+            entry = entry.next;
+        }
+        return entry == null ? null : entry.value;
     }
 
     @Override
     public int getSize() {
-        return 0;
+        return size;
+    }
+
+    private void increaseBuckets() {
+        size = 0;
+        capacity *= 2;
+        Entry<K, V>[] oldEntries = table;
+        table = new Entry[capacity];
+        for (Entry<K, V> entry : oldEntries) {
+            if (entry != null) {
+                do {
+                    put(entry.key, entry.value);
+                    entry = entry.next;
+                } while (entry != null);
+            }
+        }
+    }
+
+    private void putInBucket(K key, V value, int keyHash, int bucketIndex) {
+        Entry<K, V> entry = table[bucketIndex];
+        Entry<K, V> prevEntry = entry;
+
+        if (entry == null) {
+            table[bucketIndex] = new Entry<>(key, value);
+            size++;
+            return;
+        }
+
+        while (entry != null) {
+            if (entry.hash == keyHash && Objects.equals(entry.key, key)) {
+                entry.value = value;
+                return;
+            }
+            prevEntry = entry;
+            entry = entry.next;
+        }
+        prevEntry.next = new Entry<>(key, value);
+        size++;
+    }
+
+    private static <K> int getHash(K key) {
+        return key == null ? 0 : key.hashCode();
     }
 }