Assuming we have LRU size = 4

 import java.util.HashMap;
class Entry {
   int value;
   int key;
   Entry left;
   Entry right;
}
public class LRUCache {

    HashMap hashmap;
    Entry start, end;
    int LRU_SIZE = 4;    // Here i am setting 4 to test the LRU cache
            
  public LRUCache() {
    hashmap = new HashMap();
  }

  public int getEntry(int key) {
        if (hashmap.containsKey(key)) // Key Already Exist, just update the
        {
            Entry entry = hashmap.get(key);
            removeNode(entry);
            addAtTop(entry);
            return entry.value;
        }
        return -1;
  }

  public void putEntry(int key, int value) {
    if (hashmap.containsKey(key))     // Key Already Exist, just update the value and move it to top
    {
          Entry entry = hashmap.get(key);
          entry.value = value;
          removeNode(entry);
          addAtTop(entry);
    } else {
          Entry newnode = new Entry();
          newnode.left = null;
          newnode.right = null;
          newnode.value = value;
          newnode.key = key;
      if (hashmap.size() > LRU_SIZE)   // We have reached maxium size so need to make room for new element.
      {
          hashmap.remove(end.key);
          removeNode(end);        
          addAtTop(newnode);

      } else {
          addAtTop(newnode);
      }

          hashmap.put(key, newnode);
    }
  }
  public void addAtTop(Entry node) {
          node.right = start;
          node.left = null;
          if (start != null)
            start.left = node;
          start = node;
          if (end == null)
            end = start;
  }

  public void removeNode(Entry node) {

    if (node.left != null) {
      node.left.right = node.right;
    } else {
      start = node.right;
    }

    if (node.right != null) {
      node.right.left = node.left;
    } else {
      end = node.left;
    }
  }
  public static void main(String[] args) throws java.lang.Exception {
    // Main Function
    LRUCache lrucache = new LRUCache();
    lrucache.putEntry(1, 1);
    lrucache.putEntry(10, 15);
    lrucache.putEntry(15, 10);
    lrucache.putEntry(10, 16);
    lrucache.putEntry(12, 15);
    lrucache.putEntry(18, 10);
    lrucache.putEntry(13, 16);

    System.out.println(lrucache.getEntry(1));
    System.out.println(lrucache.getEntry(10));
    System.out.println(lrucache.getEntry(15));

  }
}