定义排序接口并实现排序功能

最新推荐文章于 2023-12-04 09:56:41 发布

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本文介绍了一个Java接口Ordered，用于定义对象的排序优先级，包括最高和最低优先级的常量，以及获取对象排序值的方法。同时提供了一个OrderUtil类，包含静态方法order，用于对实现了Ordered接口的对象列表进行排序。

public interface Ordered {

    /**
     * Useful constant for the highest precedence value.
     *
     * @see java.lang.Integer#MIN_VALUE
     */
    int HIGHEST_PRECEDENCE = Integer.MIN_VALUE;

    /**
     * Useful constant for the lowest precedence value.
     *
     * @see java.lang.Integer#MAX_VALUE
     */
    int LOWEST_PRECEDENCE = Integer.MAX_VALUE;
    /**
     * 默认值
     */
    int DEFAULT_PRECEDENCE = 0;


    /**
     * Return the order value of this object, with a
     * higher value meaning greater in terms of sorting.
     * <p>Normally starting with 0 or 1, with {@link #LOWEST_PRECEDENCE}
     * indicating greatest. Same order values will result in arbitrary
     * positions for the affected objects.
     * <p>Higher value can be interpreted as lower priority,
     * consequently the first object has highest priority
     * (somewhat analogous to Servlet "load-on-startup" values).
     * <p>Note that order values below 0 are reserved for framework
     * purposes. Application-specified values should always be 0 or
     * greater, with only framework components (internal or third-party)
     * supposed to use lower values.
     *
     * @return the order value
     * @see #LOWEST_PRECEDENCE
     */
    int getOrder();

}

public class OrderUtil {

    public static void order(List<? extends Ordered> orderList) {
        Collections.sort(orderList, new Comparator<Ordered>() {
            public int compare(Ordered o1, Ordered o2) {
                if (o1 != null && o2 != null) {
                    return o1.getOrder() > o2.getOrder() ? 1
                            : (o1.getOrder() == o2.getOrder() ? 0 : -1);
                }
                return 0;
            }
        });
    }

}