请教大家,关于 string 的 immutable - V2EX
V2EX = way to explore
V2EX 是一个关于分享和探索的地方
Sign Up Now
For Existing Member  Sign In
请不要在回答技术问题时复制粘贴 AI 生成的内容
RedBlackTree

请教大家,关于 string 的 immutable

  •  
  •   RedBlackTree Aug 17, 2021 2033 views
    This topic created in 1717 days ago, the information mentioned may be changed or developed.
    大多数语言的 string 类型是 immutable 不可变的,这个不可变是单纯地由编译器类型检查保证,还是 string 所在的内存是 read-only 呢?
    换句话来讲,是否可以在运行时,分配只读内存中的空间,创建不可变的变量呢?
    5 replies    2021-08-17 20:04:38 +08:00
    powerman
        1
    powerman  
       Aug 17, 2021
    看看 String 实现不就好了 ,java 里面的+号 也不过是一个语法糖,不过一大部分人的计算场景来讲,根本不用考虑字符串这个问题
    powerman
        2
    powerman  
       Aug 17, 2021
    @powerman 带来的性能影响问题 少之又少
    1194129822
        3
    1194129822  
       Aug 17, 2021   1
    思而不学则殆
    des
        4
    des  
       Aug 17, 2021   1
    只是编译器 or VM 保证了不变吧,看这个
    https://stackoverflow.com/questions/20945049/is-a-java-string-really-immutable
    secondwtq
        5
    secondwtq  
       Aug 17, 2021   1
    还是要分清 specification 和 implementation

    > 语言的 string 类型是 immutable 不可变的
    (是不是”大多数“就不扯了)
    这是 specification 规定的

    > 由编译器类型检查保证
    这是 implementation 用来 enforce specification 的手段

    > 所在的内存是 read-only
    这是 implementation 在特定条件下,以不违反 specification 前提做的优化
    About     Help     Advertise     Blog     API     FAQ     Solana     2674 Online   Highest 6679       Select Language
    创意工作者们的社区
    World is powered by solitude
    VERSION: 3.9.8.5 62ms UTC 12:56 PVG 20:56 LAX 05:56 JFK 08:56
    Do have faith in what you're doing.
    ubao msn snddm index pchome yahoo rakuten mypaper meadowduck bidyahoo youbao zxmzxm asda bnvcg cvbfg dfscv mmhjk xxddc yybgb zznbn ccubao uaitu acv GXCV ET GDG YH FG BCVB FJFH CBRE CBC GDG ET54 WRWR RWER WREW WRWER RWER SDG EW SF DSFSF fbbs ubao fhd dfg ewr dg df ewwr ewwr et ruyut utut dfg fgd gdfgt etg dfgt dfgd ert4 gd fgg wr 235 wer3 we vsdf sdf gdf ert xcv sdf rwer hfd dfg cvb rwf afb dfh jgh bmn lgh rty gfds cxv xcv xcs vdas fdf fgd cv sdf tert sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf sdf shasha9178 shasha9178 shasha9178 shasha9178 shasha9178 liflif2 liflif2 liflif2 liflif2 liflif2 liblib3 liblib3 liblib3 liblib3 liblib3 zhazha444 zhazha444 zhazha444 zhazha444 zhazha444 dende5 dende denden denden2 denden21 fenfen9 fenf619 fen619 fenfe9 fe619 sdf sdf sdf sdf sdf zhazh90 zhazh0 zhaa50 zha90 zh590 zho zhoz zhozh zhozho zhozho2 lislis lls95 lili95 lils5 liss9 sdf0ty987 sdft876 sdft9876 sdf09876 sd0t9876 sdf0ty98 sdf0976 sdf0ty986 sdf0ty96 sdf0t76 sdf0876 df0ty98 sf0t876 sd0ty76 sdy76 sdf76 sdf0t76 sdf0ty9 sdf0ty98 sdf0ty987 sdf0ty98 sdf6676 sdf876 sd876 sd876 sdf6 sdf6 sdf9876 sdf0t sdf06 sdf0ty9776 sdf0ty9776 sdf0ty76 sdf8876 sdf0t sd6 sdf06 s688876 sd688 sdf86