编辑代码

var num:Int = 250
//var say:String = "I want to say num to my girl friend!"
//var say:String = "I want to say " + num + "to my girl friend!"//报错
var say:String = "I want to say \(num) to my girl friend!"
print(say)

print("---------------------------------")
var code = "xF9y"
print(code.lowercased())
print(code.uppercased())

print("-------比较字符串------------")
var str1 = String("abcd")
var str2 = String("abcd")
if str1 == str2 {
    print("str1 和 str2 相同。")
} else {
    print("str1 和 str2 不同。")
}
if str1.elementsEqual(str2) {
    print("str1 和 str2 相同。")
} else {
    print("str1 和 str2 不同。")
}

print("=========================")
var fileName = "Sun.java"
print(fileName.hasPrefix("S"))
print(fileName.hasSuffix("java"))