diff --git a/pom.xml b/pom.xml
index 36c092b..345df07 100644
--- a/pom.xml
+++ b/pom.xml
@@ -18,8 +18,8 @@
                 <version>3.3</version>
                 <configuration>
                     <encoding>UTF-8</encoding>
-                    <source>1.8</source>
-                    <target>1.8</target>
+                    <source>11</source>
+                    <target>11</target>
                 </configuration>
             </plugin>
         </plugins>
@@ -27,10 +27,17 @@
 
     <dependencies>
         <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <version>4.12</version>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>5.9.2</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.23.1</version>
+            <scope>test</scope>
+        </dependency>
+
     </dependencies>
 </project>
diff --git a/src/main/java/de/comparus/opensource/longmap/LongMapImpl.java b/src/main/java/de/comparus/opensource/longmap/LongMapImpl.java
index 2f0b54b..ff0caac 100644
--- a/src/main/java/de/comparus/opensource/longmap/LongMapImpl.java
+++ b/src/main/java/de/comparus/opensource/longmap/LongMapImpl.java
@@ -1,43 +1,234 @@
 package de.comparus.opensource.longmap;
 
+import java.lang.reflect.Array;
+
 public class LongMapImpl<V> implements LongMap<V> {
-    public V put(long key, V value) {
-        return null;
+
+  private static final int DEFAULT_CAPACITY = 16;
+  private static final float DEFAULT_LOAD_FACTOR = 0.75f;
+
+  private int capacity;
+  private float loadFactor;
+  private int size;
+  public Entry<V>[] buckets;
+
+  Class<V> type;
+
+  public LongMapImpl(Class<V> type) {
+    this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, type);
+  }
+
+  public LongMapImpl(int capacity, float loadFactor, Class<V> type) {
+    if (capacity <= 0) {
+      throw new IllegalArgumentException("Invalid capacity: " + capacity);
     }
+    if (loadFactor <= 0 || loadFactor > 1) {
+      throw new IllegalArgumentException("Invalid load factor: " + loadFactor);
+    }
+
+    this.type = type;
+
+    this.capacity = capacity;
+    this.loadFactor = loadFactor;
+    this.size = 0;
+    this.buckets = new Entry[capacity];
+  }
+
+  public V put(long key, V value) {
+    int bucketIndex = getBucketIndex(key, capacity);
+    Entry<V> bucket = buckets[bucketIndex];
+
+    if (bucket == null) {
+      buckets[bucketIndex] = new Entry(key, value);
+    } else {
+      Entry<V> prev = null;
+      while (bucket != null) {
+        if (bucket.getKey() == key) {
+          V oldValue = bucket.getValue();
+          bucket.setValue(value);
+          return oldValue;
+        }
+        prev = bucket;
+        bucket = bucket.next;
+      }
 
-    public V get(long key) {
-        return null;
+      prev.next = new Entry(key, value);
     }
 
-    public V remove(long key) {
-        return null;
+    size++;
+
+    if (size > capacity * loadFactor) {
+      resize();
     }
 
-    public boolean isEmpty() {
-        return false;
+    return null;
+  }
+
+  public V get(long key) {
+    int bucketIndex = getBucketIndex(key, capacity);
+    Entry<V> bucket = buckets[bucketIndex];
+
+    if (bucket != null) {
+      while (bucket != null) {
+        if (bucket.getKey() == key) {
+          return bucket.getValue();
+        }
+        bucket = bucket.next;
+      }
     }
 
-    public boolean containsKey(long key) {
-        return false;
+    return null;
+  }
+
+  public V remove(long key) {
+    int bucketIndex = getBucketIndex(key, capacity);
+    Entry<V> bucket = buckets[bucketIndex];
+
+    if (bucket != null) {
+      Entry<V> prev = null;
+      while (bucket != null) {
+        if (bucket.getKey() == key) {
+          V value = bucket.getValue();
+          if (prev == null) {
+            if (bucket.next != null) {
+              buckets[bucketIndex] = bucket.next;
+            } else {
+              buckets[bucketIndex] = null;
+            }
+          } else {
+            prev.next = null;
+          }
+          size--;
+          return value;
+        }
+        prev = bucket;
+        bucket = bucket.next;
+      }
     }
 
-    public boolean containsValue(V value) {
-        return false;
+    return null;
+  }
+
+  public boolean isEmpty() {
+    return size == 0;
+  }
+
+  public boolean containsKey(long key) {
+    int bucketIndex = getBucketIndex(key, capacity);
+    Entry<V> bucket = buckets[bucketIndex];
+
+    if (bucket != null) {
+      while (bucket != null) {
+        if (bucket.getKey() == key) {
+          return true;
+        }
+        bucket = bucket.next;
+      }
     }
+    return false;
+  }
 
-    public long[] keys() {
-        return null;
+  public boolean containsValue(V value) {
+    for (Entry<V> bucket : buckets) {
+      while (bucket != null) {
+        if (bucket.getValue().equals(value)) {
+          return true;
+        }
+        bucket = bucket.next;
+      }
     }
 
-    public V[] values() {
-        return null;
+    return false;
+  }
+
+  public long[] keys() {
+    long[] keys = new long[size];
+    int index = 0;
+
+    for (Entry<V> bucket : buckets) {
+      while (bucket != null) {
+        keys[index++] = bucket.getKey();
+        bucket = bucket.next;
+      }
     }
 
-    public long size() {
-        return 0;
+    return keys;
+  }
+
+  public V[] values() {
+    V[] values = (V[]) Array.newInstance(type, size);
+    int index = 0;
+
+    for (Entry<V> bucket : buckets) {
+      while (bucket != null) {
+        values[index++] = bucket.getValue();
+        bucket = bucket.next;
+      }
+    }
+
+    return values;
+  }
+
+  public long size() {
+    return size;
+  }
+
+  public void clear() {
+    size = 0;
+    buckets = new Entry[capacity];
+  }
+
+
+  private int getBucketIndex(long key, int capacity) {
+    return (int) Math.abs(key) % capacity;
+  }
+
+  private void resize() {
+    int newCapacity = capacity + capacity/2;
+    if (newCapacity < 0) {
+      throw new IllegalArgumentException("Couldn't be resized. Maximum size has been reached.");
+    }
+    Entry<V>[] newBuckets = new Entry[newCapacity];
+
+    for (Entry<V> bucket : buckets) {
+      while (bucket != null) {
+        int newBucketIndex = getBucketIndex(bucket.getKey(), newCapacity);
+        Entry<V> newBucket = newBuckets[newBucketIndex];
+        if (newBucket == null) {
+          newBuckets[newBucketIndex] = bucket;
+        } else {
+          newBucket.next = bucket;
+        }
+        bucket = bucket.next;
+      }
+    }
+
+    capacity = newCapacity;
+    buckets = newBuckets;
+  }
+
+  private static class Entry<V> {
+
+    private long key;
+    private V value;
+
+    private Entry<V> next;
+
+    public Entry(long key, V value) {
+      this.key = key;
+      this.value = value;
     }
 
-    public void clear() {
+    public long getKey() {
+      return key;
+    }
+
+    public V getValue() {
+      return value;
+    }
 
+    public void setValue(V value) {
+      this.value = value;
     }
+  }
 }
diff --git a/src/main/test/java/de/comparus/opensource/longmap/LongMapTest.java b/src/main/test/java/de/comparus/opensource/longmap/LongMapTest.java
new file mode 100644
index 0000000..1990359
--- /dev/null
+++ b/src/main/test/java/de/comparus/opensource/longmap/LongMapTest.java
@@ -0,0 +1,92 @@
+package de.comparus.opensource.longmap;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Tag;
+import org.junit.jupiter.api.Test;
+
+import java.util.stream.LongStream;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertAll;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+@Tag("Unit")
+public class LongMapTest {
+
+  public static final long GENERATED_AMOUNT = 10;
+
+  @Test
+  @DisplayName("Complex test of get, contains key/value, put, resize methods")
+  public void longMapTest() {
+    final long TESTED_AMOUNT_OF_ENTRIES = 10000;
+    LongMap<Long> map = generateMapWithValues(TESTED_AMOUNT_OF_ENTRIES);
+    assertMapRange(map, -TESTED_AMOUNT_OF_ENTRIES, TESTED_AMOUNT_OF_ENTRIES);
+  }
+
+  @Test
+  public void removeTest() {
+    LongMap<Long> map = generateMapWithValues(GENERATED_AMOUNT);
+    for(long i = 1; i <= GENERATED_AMOUNT; i++) {
+      map.remove(i);
+    }
+    assertEquals(map.size(), 11);
+    assertMapRange(map, -GENERATED_AMOUNT, 0);
+  }
+
+  @Test
+  @DisplayName("Complex test of clear, isEmpty methods")
+  public void clearTest() {
+    LongMap<Long> map = generateMapWithValues(GENERATED_AMOUNT);
+    map.clear();
+    assertAll(
+        () -> assertEquals(map.size(), map.values().length),
+        () -> assertTrue(map.isEmpty())
+    );
+  }
+
+  @Test
+  public void valuesTest() {
+    LongMap<Long> map = generateMapWithValues(GENERATED_AMOUNT);
+    Long [] valuesOfMap = map.values();
+    Long [] expectedValuesOfMap = Stream
+        .iterate(-GENERATED_AMOUNT, i -> i+1)
+        .limit(20)
+        .toArray(Long[]::new);
+    assertAll(
+        () -> assertEquals( 20, valuesOfMap.length),
+        () -> assertThat(valuesOfMap).containsOnly(expectedValuesOfMap)
+    );
+  }
+
+  @Test
+  public void keysTest() {
+    LongMap<Long> map = generateMapWithValues(GENERATED_AMOUNT);
+    long [] keysOfMap = map.keys();
+    long [] expectedKeysOfMap = LongStream
+        .iterate(-GENERATED_AMOUNT, i -> i+1)
+        .limit(20)
+        .toArray();
+    assertAll(
+        () -> assertEquals( 20, keysOfMap.length),
+        () -> assertThat(keysOfMap).containsOnly(expectedKeysOfMap)
+    );
+  }
+
+  private LongMap<Long> generateMapWithValues(long TESTED_AMOUNT_OF_ENTRIES) {
+    LongMap<Long> map = new LongMapImpl<>(Long.class);
+    for (long i = -TESTED_AMOUNT_OF_ENTRIES; i < TESTED_AMOUNT_OF_ENTRIES; i++) {
+      map.put(i, i);
+    }
+    return map;
+  }
+
+  private static void assertMapRange(LongMap<Long> map, long minBound, long maxBound) {
+    for (long i = minBound; i < maxBound; i++) {
+      assertEquals(i, map.get(i));
+      assertTrue(map.containsKey(i));
+      assertTrue(map.containsValue(i));
+    }
+  }
+}