func testCompare()  {
        
        let str1 = "hello"
        let str2 = "world"
        print(str1.compare(str2).rawValue)

        
        let num1 = "1"
        let num2 = "2"
        print(num2.compare(num1).rawValue)
        
        
        let str11 = "hello"
        let str22 = "World"
        //compare区分大小写
        print(str11.compare(str22).rawValue)
        
        //compare不区分大小写  设置options：caseInsensitive
        print(str11.compare(str22, options: .caseInsensitive, range: nil, locale: nil).rawValue)
    }