var stringList1= [String]()//创建String类型空数组
var stringList2= ["1","3","5","7","zoo","9","zoo"]
var stringList3:[String] = ["2","4","6","apple","8","10"]
stringList1+=stringList2//把stringList2数组的所有元素添加到stringList1的末尾
print("stringList1: \(stringList1)")//输出stringList1
stringList1+=stringList3//把stringList3数组的所有元素添加到stringList1的末尾
print("stringList1: \(stringList1)")//输出stringList1
运行结果：
stringList1: ["1","3","5","7","zoo","9","zoo"]
stringList1: ["1","3","5","7","zoo","9","zoo","2","4","6","apple","8","10"]
以上输出结果的元素无序排列，可使用数组的 sort() 方法或 sortInPlace() 方法排序，两者不同在于
sort()方法有返回值，返回一个新数组，而不改变原数组的值：
print("After sort: \(stringList1.sort())")
print("stringList1: \(stringList1)")
运行结果：
After sort: ["1","10","2","3","4","5","6","7","8","9","apple","zoo","zoo"]
stringList1: ["1","3","5","7","zoo","9","zoo","2","4","6","apple","8","10"]
sortInPlace()方法无返回值，会改变原数组的值：
stringList1.sortInPlace()
print("stringList1: \(stringList1)")
运行结果：
stringList1: ["1","10","2","3","4","5","6","7","8","9","apple","zoo","zoo"]
+=运算符只能用于数组之间，不能添加单个元素：
var str="myString"
stringList1+=str//此行报错：Binary operator '+=' cannot be applied to operands of type '[String]' and 'String'
