否则速度慢四五倍！！！正确的做法是：在for循环外面new一个对象，每次循环调用一次clear！！！

原文地址：https://blog.csdn.net/zwcwu31/article/details/81510562?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522168904449916800185828444%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=168904449916800185828444&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~first_rank_ecpm_v1~rank_v31_ecpm-22-81510562-null-null.142^v88^control_2,239^v2^insert_chatgpt&utm_term=java%E4%BC%98%E5%8C%96