java string 类的使用。主要是对在已经存在的四个string串，系统随机生成一个单词，如果该单词和四个string中任何一个匹配则成功，否则继续。-java string class to use. Mainly in the four string string already exists, the system randomly generates a word, if the words and match any of the four string is successful, otherwise continue.