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The Cloud Services Integration Platform is a SoA implementation to offer a Model-as-a-Service framework, Application Programming Interface, deployment infrastructure, and service implementations for environmental modeling.

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package csip.utils;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * LRU cache.
 *
 * @author od
 */
public class LRUCache {

  static final int DEFAULT_SIZE = 16;

  Map m = new LinkedHashMap<>();
  int size;
  K _key;
  V _val;


  public LRUCache(int size) {
    if (size < 1) {
      throw new IllegalArgumentException("size >= 1!");
    }
    this.size = size;
  }


  public LRUCache() {
    this(DEFAULT_SIZE);
  }


  public V put(K key, V val) {
    V prev = m.put(_key = key, _val = val);
    if (m.size() > size) {
      // evict  the first element
      K first = m.keySet().iterator().next();
      m.remove(first);
    }
    return prev;
  }


  public V get(K key) {
    // accessing the last one again? 
    if (key.equals(_key)) {
      return _val;
    }
    if (m.containsKey(key)) {
      V val = m.get(key);
      // remove it from wherever it is in the cache 
      m.remove(key);
      // put it at the end.
      m.put(_key = key, _val = val);
      return val;
    }
    return null;
  }


  public void clear() {
    m.clear();
  }


  public static void main(String[] args) {
    LRUCache c = new LRUCache<>();
    System.out.println(c.put("ff", "1"));
    System.out.println(c.put("ff2", "2"));
    System.out.println(c.put("ff3", "3"));
    System.out.println(c.m);
  }

}