LRU cache in java

lru_java.java

// Lru cache in java with custom doubly linked list.

import java.util.HashSet;
import java.util.Iterator;

public class LRURunner {
  public static void main(String[] args) {
    Lru lru = new Lru(3);

    lru.get("1");
    lru.get("2");
    lru.get("3");
    lru.get("4");

    lru.showList();
  }
}

public class Lru {
  private LinkedList linkedList;
  private java.util.HashSet<String> lruHashSet;
  private int lruCapacity;

  public Lru(int capacity) {
    lruCapacity = capacity;
    lruHashSet = new HashSet<>();
    linkedList = new LinkedList();
  }

  public void showList() {
    linkedList.showList();
  }

  public void get(String value) {
    if (!lruHashSet.contains(value)) {
      if(lruCapacity == lruHashSet.size()){
        linkedList.popTail();
        lruHashSet.remove(value);
      }
    } else {
      linkedList.removeNode(value);
    }

    linkedList.enqueue(value);
    lruHashSet.add(value);
  }
}

public class LinkedList {
  private Node head;
  private Node tail;

  public LinkedList() {
    head = null;
    tail = null;
  }

  public void showList() {
    Node tmpNode = head;
    while (tmpNode != null) {
      System.out.println(tmpNode.getValue());
      tmpNode = tmpNode.getNextNode();
    }
  }

  public void popTail() {
    Node prevNode = tail.getPreviousNode();
    prevNode.setNextNode(null);
    tail = prevNode;
  }

  public void removeNode(String value) {
    Node tmpNode = head;
    while (tmpNode != null) {
      if (tmpNode.equals(value)) {
        Node prevNode = tmpNode.getPreviousNode();
        Node nextNode = tmpNode.getNextNode();

        prevNode.setNextNode(nextNode);
        nextNode.setPreviousNode(prevNode);
      }
      tmpNode = tmpNode.getNextNode();
    }
  }

  public void enqueue(String value) {
    Node node = new Node(value);
    if (head == null) {
      head = node;
      tail = node;
    } else {
      Node prevHead = head;

      head = node;
      head.setNextNode(prevHead);
      prevHead.setPreviousNode(head);
    }
  }
}

public class Node {
  private String value;
  private Node next;
  private Node previous;

  public Node(String v) {
    value = v;
    next = null;
    previous = null;
  }

  public Node getNextNode() {
    return next;
  }

  public Node getPreviousNode() {
    return previous;
  }

  public String getValue() {
    return value;
  }

  public void setNextNode(Node node) {
    next = node;
  }

  public void setPreviousNode(Node node) {
    previous = node;
  }
}