.模拟植树活动，编写一个Java应用程序，在主线程中创建3个线程：“挖树坑”、“栽树苗”和“浇水”，实现它们之间的协同工作。-Simulated tree planting activities, the preparation of a Java application, the main thread creates three threads: " dig Pits" , " planted trees" and " watering"