代码实现了经典的三种join算法，并赋有测试文件，编译成功，直接可以运行-Code of the three classical join algorithms, and endowed with the test file, compile successfully, you can run directly

oins two records from two different * input flows based on specified key. The flow on port 0 is the driver, the flow * on port 1 is the slave. First, all records from slave flow are read and stored in * hash table. Then for every record from