采用多种方法实现求一个整形数组的第二大数，同时提供了一个求任意大数的函数。有详细代码注释及主要思路、时间复杂度的分析。-Many ways to search the second maximum number of an array of Integer,meantime there is one function can finish searching　any maximum number.There are enough comments and the ideas to design,the complexity of every algorithm.