类名一一对应内容，分别是：
* MainActivity——RxJava基础用法
* simplestAty——RxJava简单实例
* timer——延时操作
* interval——周期性操作
* twoexample——两个RxJava初始化demo
* schedulePeriodically——使用RxJava做轮询请求
* merge——合并两个数据源
* map_flatmap——RxJava实现变换
* foreach——实现数组，List遍历
* concat——实现比较一堆item，一旦满足后面的item不执行的功能
* lifecycle——回收Observable以防止内存泄漏
以上合集涵盖了大部分RxJava语法与使用场景
每个实例都可单独运行，打印输出结果
希望给正在学习RxJava中的你一点启发
持续更新中，欢迎pull requests.
博客地址：RxJava使用场景总结
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