用Java语言编程运行LRU算法或CLOCK/改进算法等置换算法

以下是Java语言实现LRU算法的示例代码：

import java.util.HashMap;
import java.util.Map;

public class LRUCache<K, V> {
    private int capacity;
    private Map<K, Node<K, V>> map;
    private Node<K, V> head;
    private Node<K, V> tail;

    public LRUCache(int capacity) {
        this.capacity = capacity;
        map = new HashMap<>();
        head = new Node<>(null, null);
        tail = new Node<>(null, null);
        head.next = tail;
        tail.prev = head;
    }

    public V get(K key) {
        Node<K, V> node = map.get(key);
        if (node == null) {
            return null;
        }
        remove(node);
        addFirst(node);
        return node.value;
    }

    public void put(K key, V value) {
        Node<K, V> node = map.get(key);
        if (node != null) {
            node.value = value;
            remove(node);
            addFirst(node);
        } else {
            if (map.size() == capacity) {
                map.remove(tail.prev.key);
                remove(tail.prev);
            }
            node = new Node<>(key, value);
            map.put(key, node);
            addFirst(node);
        }
    }

    private void remove(Node<K, V> node) {
        node.prev.next = node.next;
        node.next.prev = node.prev;
    }

    private void addFirst(Node<K, V> node) {
        node.next = head.next;
        node.prev = head;
        head.next.prev = node;
        head.next = node;
    }

    private static class Node<K, V> {
        K key;
        V value;
        Node<K, V> prev;
        Node<K, V> next;

        Node(K key, V value) {
            this.key = key;
            this.value = value;
        }
    }
}

以下是Java语言实现CLOCK/改进算法的示例代码：

import java.util.HashMap;
import java.util.Map;

public class ClockCache<K, V> {
    private int capacity;
    private Map<K, Node<K, V>> map;
    private Node<K, V> head;
    private Node<K, V> tail;
    private int pointer;

    public ClockCache(int capacity) {
        this.capacity = capacity;
        map = new HashMap<>();
        head = new Node<>(null, null);
        tail = new Node<>(null, null);
        head.next = tail;
        tail.prev = head;
        pointer = 0;
    }

    public V get(K key) {
        Node<K, V> node = map.get(key);
        if (node == null) {
            return null;
        }
        node.referenced = true;
        return node.value;
    }

    public void put(K key, V value) {
        Node<K, V> node = map.get(key);
        if (node != null) {
            node.value = value;
            node.referenced = true;
        } else {
            if (map.size() == capacity) {
                while (true) {
                    if (pointer == 0) {
                        pointer = 1;
                    } else {
                        Node<K, V> p = head.next;
                        while (p != tail) {
                            if (!p.referenced) {
                                break;
                            }
                            p.referenced = false;
                            p = p.next;
                        }
                        if (p == tail) {
                            p = head.next;
                            while (p != tail) {
                                p.referenced = false;
                                p = p.next;
                            }
                        }
                        pointer = 0;
                        remove(p);
                        map.remove(p.key);
                        break;
                    }
                }
            }
            node = new Node<>(key, value);
            map.put(key, node);
            addFirst(node);
        }
    }

    private void remove(Node<K, V> node) {
        node.prev.next = node.next;
        node.next.prev = node.prev;
    }

    private void addFirst(Node<K, V> node) {
        node.next = head.next;
        node.prev = head;
        head.next.prev = node;
        head.next = node;
    }

    private static class Node<K, V> {
        K key;
        V value;
        boolean referenced;
        Node<K, V> prev;
        Node<K, V> next;

        Node(K key, V value) {
            this.key = key;
            this.value = value;
            this.referenced = true;
        }
    }
}