阅读他人代码：一（node以及接口的new使用）

1.关于内部类新的使用方法：
package com.iluwatar.caching;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class LruCache {

  private static final Logger LOGGER = LoggerFactory.getLogger(LruCache.class);

  class Node {
    String userId;
    UserAccount userAccount;
    Node previous;
    Node next;

    public Node(String userId, UserAccount userAccount) {
      this.userId = userId;
      this.userAccount = userAccount;
    }
  }

  int capacity;
  Map<String, Node> cache = new HashMap<>();
  Node head;
  Node end;

  public LruCache(int capacity) {
    this.capacity = capacity;
  }

  /**
   * Get user account
   */
  public UserAccount get(String userId) {
    if (cache.containsKey(userId)) {
      Node node = cache.get(userId);
      remove(node);
      setHead(node);
      return node.userAccount;
    }
    return null;
  }

  /**
   * Remove node from linked list.
   */
  public void remove(Node node) {
    if (node.previous != null) {
      node.previous.next = node.next;
    } else {
      head = node.next;
    }
    if (node.next != null) {
      node.next.previous = node.previous;
    } else {
      end = node.previous;
    }
  }

  /**
   * Move node to the front of the list.
   */
  public void setHead(Node node) {
    node.next = head;
    node.previous = null;
    if (head != null) {
      head.previous = node;
    }
    head = node;
    if (end == null) {
      end = head;
    }
  }

  /**
   * Set user account
   */
  public void set(String userId, UserAccount userAccount) {
    if (cache.containsKey(userId)) {
      Node old = cache.get(userId);
      old.userAccount = userAccount;
      remove(old);
      setHead(old);
    } else {
      Node newNode = new Node(userId, userAccount);
      if (cache.size() >= capacity) {
        LOGGER.info("# Cache is FULL! Removing {} from cache...", end.userId);
        cache.remove(end.userId); // remove LRU data from cache.
        remove(end);
        setHead(newNode);
      } else {
        setHead(newNode);
      }
      cache.put(userId, newNode);
    }
  }

  public boolean contains(String userId) {
    return cache.containsKey(userId);
  }

  /**
   * Invalidate cache for user
   */
  public void invalidate(String userId) {
    Node toBeRemoved = cache.remove(userId);
    if (toBeRemoved != null) {
      LOGGER.info("# {} has been updated! Removing older version from cache...", userId);
      remove(toBeRemoved);
    }
  }

  public boolean isFull() {
    return cache.size() >= capacity;
  }

  public UserAccount getLruData() {
    return end.userAccount;
  }

  /**
   * Clear cache
   */
  public void clear() {
    head = null;
    end = null;
    cache.clear();
  }

  /**
   * Returns cache data in list form.
   */
  public List<UserAccount> getCacheDataInListForm() {
    List<UserAccount> listOfCacheData = new ArrayList<>();
    Node temp = head;
    while (temp != null) {
      listOfCacheData.add(temp.userAccount);
      temp = temp.next;
    }
    return listOfCacheData;
  }

  /**
   * Set cache capacity
   */
  public void setCapacity(int newCapacity) {
    if (capacity > newCapacity) {
      clear(); // Behavior can be modified to accommodate for decrease in cache size. For now, we'll
               // just clear the cache.
    } else {
      this.capacity = newCapacity;
    }
  }
}

2.接口的new使用形式：

Callback callback = new Callback() {
      @Override
      public void call() {
        LOGGER.info("I'm done now.");
      }
    };

public interface Callback {

  void call();
}