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1、Initializing an Empty String
var emtyString = “”
var anotherEmptyString = String()
两种初始化方法
2、Find out whether a String value is empty by checking its Boolean isEmpty property
if emptyString.isEmpy {
print(“Nothing to see here”)
}
3、override 计算机里面是覆盖的意思
5、for character in “Dog!