ehcache memcache 区别_ehcache缓存原理_ehcache使用(10)

注：

hit值小的缓存淘汰。

3、FIFOPolicy代码如下：

public class FifoPolicy extends AbstractPolicy {

    /**
     * The name of this policy as a string literal
     */
     public static final String NAME = "FIFO";

    /**
     * @return the name of the Policy. Inbuilt examples are LRU, LFU and FIFO.
     */
    public String getName() {
        return NAME;
    }

    /**
     * Compares the desirableness for eviction of two elements
     *
     * Compares hit counts. If both zero,
     *
     * @param element1 the element to compare against
     * @param element2 the element to compare
     * @return true if the second element is preferable to the first element for ths policy
     */
    public boolean compare(Element element1, Element element2) {
        return element2.getLatestOfCreationAndUpdateTime() < element1.getLatestOfCreationAndUpdateTime();

    }
}

注：

以creationAndUpdateTime最新或者最近的缓存淘汰。

4、这三个策略类统一继承AbstractPolicy抽类

最关键的就是下面这个方法：

public Element selectedBasedOnPolicy(Element[] sampledElements, Element justAdded) {
        //edge condition when Memory Store configured to size 0
        if (sampledElements.length == 1) {
            return sampledElements[0];
        }
        Element lowestElement = null;
        for (Element element : sampledElements) {
            if (element == null) {
                continue;
            }
            if (lowestElement == null) {
                if (!element.equals(justAdded)) {
                    lowestElement = element;
                }
            } else if (compare(lowestElement, element) && !element.equals(justAdded)) {
                lowestElement = element;
            }

        }
        return lowestElement;
    }

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