关于java:设计模式

懒汉式单例

public class RecommendPresenter {    private RecommendPresenter() {    }    private static RecommendPresenter sInstance = null;    /**     * 获取单例对象     * @return     */    public static RecommendPresenter getInstance() {        if (sInstance == null) {            synchronized (RecommendPresenter.class) {                if (sInstance == null) {                    sInstance = new RecommendPresenter();                }            }        }    }}