什么是线程安全？

参考

1，https://blog.csdn.net/csdnnews/article/details/82321777?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165957849316782388087536%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=165957849316782388087536&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~top_positive~default-2-82321777-null-null.142^v39^pc_rank_34_queryrelevant0&utm_term=%E7%BA%BF%E7%A8%8B%E5%AE%89%E5%85%A8&spm=1018.2226.3001.4187

2，https://blog.csdn.net/weixin_43464372/article/details/108233648?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165957849316782388087536%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=165957849316782388087536&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~top_click~default-3-108233648-null-null.142^v39^pc_rank_34_queryrelevant0&utm_term=%E7%BA%BF%E7%A8%8B%E5%AE%89%E5%85%A8&spm=1018.2226.3001.4187