{"id":10006931,"date":"2022-11-28T21:11:02","date_gmt":"2022-11-28T13:11:02","guid":{"rendered":"https:\/\/ityet.com\/?p=10006931"},"modified":"2022-11-28T21:11:02","modified_gmt":"2022-11-28T13:11:02","slug":"%e4%bb%8e-java-%e5%88%b0-kotlin-%e4%bb%8b%e7%bb%8d-kotlin","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10006931","title":{"rendered":"\u4ece Java \u5230 Kotlin – \u4ecb\u7ecd Kotlin"},"content":{"rendered":"

B\u7ad9\u89c6\u9891\uff1ahttps:\/\/www.bilibili.com\/vide…<\/a><\/p><\/blockquote>\n

\n

\u8bed\u6cd5\u5c42\u9762<\/h2>\n
    \n
  1. \n

    \u53ef\u7a7a\u5bf9\u8c61\uff08\u548c C# \u7684 <Nullable>enabled<\/Nullable><\/code> \u76f8\u4f3c\uff09 <\/p>\n

    Int<\/code> \u548c Int?<\/code> \u662f\u4e24\u79cd\u4e0d\u540c\u7684\u7c7b\u578b\uff1bString<\/code>\u548c String?<\/code> \u4e5f\u662f\u4e24\u79cd\u4e0d\u540c\u7684\u7c7b\u578b\uff08\u524d\u8005\u662f\u540e\u8005\u7684\u5b50\u7c7b\u578b\uff09<\/p>\n

    var a: Int = 0;\nvar b: Int? = 0;\n\na = b;  \/\/ \u21d0 \u4e0d\u80fd\u5c06 Int? \u8d4b\u503c\u7ed9 Int\nb = a; <\/code><\/pre>\n<\/li>\n
  2. \n
    \u4e0d\u53ef\u53d8\u7c7b\u578b\/\u53ef\u53d8\u7c7b\u578b<\/p>\n
    val<\/code> \u58f0\u660e\u4e0d\u53ef\u53d8\u53d8\u91cf\uff0c\u4e0d\u53ef\u518d\u8d4b\u503c\uff1bvar<\/code> \u58f0\u660e\u53ef\u53d8\u53d8\u91cf\uff0c\u80fd\u518d\u8d4b\u503c\u3002<\/p>\n
    var a = 0;\nval b = 1;\na = b;\nb = a;  \/\/ \u21d0 \u4e0d\u80fd\u5bf9 val \u53d8\u91cf\u8d4b\u503c<\/code><\/pre>\n<\/li>\n
  3. \n
    \u5b57\u7b26\u4e32\u63d2\u503c<\/p>\n
    val PI = 3.1415926\n\nval s1 = "PI is ${PI}";    \/\/ PI is 3.1415926\nval s2 = "PI is ${String.format("%.2f", PI)}";  \/\/ PI is 3.14<\/code><\/pre>\n
    \u5b57\u7b26\u4e32\u63d2\u503c\u8bed\u6cd5\u4e0d\u652f\u6301\u8bbe\u7f6e\u683c\u5f0f\uff08\u8fd9\u70b9\u4e0d\u5982 C# \u65b9\u4fbf\uff09<\/p><\/blockquote>\n<\/li>\n
  4. \n
    \u5bf9\u51fd\u6570\u5f0f\u7f16\u7a0b\u7684\u652f\u6301\uff0c\u4e00\u5207\u90fd\u662f\u8868\u8fbe\u5f0f<\/p>\n
    \u6ca1\u6709\u6761\u4ef6\uff08\u4e09\u76ee\uff09\u8fd0\u7b97\u7b26\uff0c\u56e0\u4e3a if<\/code> \u5206\u652f\u5c31\u80fd\u505a\u5230\uff08\u53ea\u662f\u5199\u8d77\u6765\u5b57\u591a\u4e00\u70b9\uff09<\/p>\n
    fun fixInt(value: Int?): Int {\n    val n = value ?: 0;\n    return if (n >= 0) n else -n;\n    \/\/ C# \u7684 int? \u53ef\u4ee5\u53c2\u4e0e\u8fd0\u7b97\uff0c\u8fd9\u70b9\u4e0d\u540c\n}<\/code><\/pre>\n
    when<\/code> \u751a\u81f3 try ... catch<\/code> \u90fd\u53ef\u4ee5\u4f5c\u4e3a\u8868\u8fbe\u5f0f<\/p>\n
    fun devide(m: Int, n: Int) {\n    return try {\n        m \/ n\n    } catch (e: ArithmeticException) {\n        0\n    }\n}<\/code><\/pre>\n<\/li>\n
  5. \n
    \u51fd\u6570\u5f0f\u7f16\u7a0b\u652f\u6301\uff1awith<\/code>\u3001also<\/code>\u3001let<\/code>\u3001run<\/code>\u3001apply<\/code><\/p>\n
    \u4e0a\u9762\u7684 fixInt<\/code> \u53ef\u4ee5\u7528 let<\/code> \u6765\u6539\u5199\uff0c\u6ce8\u610f\u662f ?.let<\/code> \u8868\u793a let<\/code> \u5757\u91cc\u7684 it<\/code> \u662f\u4e0d\u542b\u7a7a\u7684\u7c7b\u578b<\/p>\n
    fun fixInt(value: Int?): Int {\n    return value?.let { if (it >= 0) it else -it } ?: 0\n}<\/code><\/pre>\n
    with(obj)<\/code> \u5757\u4e2d\u4f1a\u628a this<\/code> \u5f15\u7528\u5230 obj<\/code> \u5bf9\u8c61\u4e0a\u53bb\uff0c\u800c this.<\/code> \u5728\u4e0d\u51b2\u7a81\u7684\u60c5\u51b5\u4e0b\u662f\u53ef\u4ee5\u7701\u7565\u7684<\/p>\n
    with ("Hello World") {\n    println("`${this}` has ${length} characters")\n}\n\/\/ `Hello World` has 11 characters<\/code><\/pre>\n
    let<\/code> \u3001also<\/code>\u3001run<\/code>\u3001apply<\/code> \u90fd\u662f\u901a\u8fc7\u70b9\u53f7 (.<\/code>) \u8c03\u7528\uff0c\u524d\u4e24\u4e2a\u5f15\u5165 it<\/code>\uff08\u6216\u81ea\u5b9a\u4e49\u53d8\u91cf\uff09\uff0c\u540e\u4e24\u4e2a\u5f15\u5165 this<\/code>\uff1balso<\/code> \u548c apply<\/code> \u8fd4\u56de\u8c03\u7528\u8005\uff0c\u5176\u4ed6\u7684\u8fd4\u56de\u6700\u540e\u4e00\u884c\u7684\u8ba1\u7b97\u7ed3\u679c\u3002<\/p>\n<\/li>\n
  6. \u5c5e\u6027\uff08\u53bb getter\/setter\uff09<\/li>\n
  7. \n
    \u6269\u5c55\u65b9\u6cd5<\/p>\n
    fun String.blabla() { ... }<\/code><\/pre>\n
    \u611f\u89c9\u6bd4 C# \u7684\u66f4\u5408\u7406\uff0c\u4f46\u662f\u4e0d\u80fd\u4f5c\u4e3a\u9759\u6001\u51fd\u6570\u8c03\u7528\uff08\u867d\u7136\u672c\u8d28\u5c31\u662f\u9759\u6001\u51fd\u6570\uff09<\/p>\n<\/li>\n
  8. \u65e0\u5dee\u522b\u7684 Lambda\uff08\u60f3\u60f3 Consumer<\/code>\uff0cRunable<\/code> \u7b49\uff0c\u76f8\u540c\u7b7e\u540d\u4f46\u4e0d\u540c\u63a5\u53e3\u7684 Lambda \u4e0d\u80fd\u4e92\u6362\uff09<\/li>\n
  9. \n
    \u5bf9\u8c61\u89e3\u6784<\/p>\n
    operator fun componentN()<\/code> \u64cd\u4f5c\u7b26\u65b9\u6cd5\uff0c\u7528\u4e8e\u89e3\u6784\u3002N<\/code> \u4ece 1 \u5f00\u59cb\uff0c\u6309\u987a\u5e8f\u9012\u589e\u3002<\/p>\n<\/li>\n
  10. \n
    when \u5206\u652f\uff08Java 12 \u6709 switch \u8868\u8fbe\u5f0f\uff09<\/p>\n
     when (view) {\n     is TextView -> toast(view.text)\n     is RecyclerView -> toast("Item count = ${view.adapter.itemCount}")\n     is SearchView -> toast("Current query: ${view.query}")\n     else -> toast("View type not supported")\n }<\/code><\/pre>\n<\/li>\n<\/ol>\n
    \u5de5\u5177\uff08\u6848\u4f8b\u6f14\u793a\uff09<\/h2>\n
      \n
    1. \u8fd4\u8f6c\u4e00\u4e2a\u6570\u7ec4 int[]<\/code><\/li>\n
    2. \u5b57\u7b26\u4e32\u5de5\u5177\u51fd\u6570\uff0c\u6bd4\u5982 padStart<\/code>, orEmpty<\/code> \u7b49<\/li>\n
    3. \u7c7b\u4f3c stream\uff0c\u4f46\u66f4\u7b80\u6d01\uff0cforEachIndexed<\/code><\/li>\n
    4. \u5feb\u901f\u521b\u5efa List \u548c Map<\/li>\n
    5. \u628a\u4e00\u5927\u65ad byte[]<\/code> \u8f6c\u6210\u5341\u516d\u8fdb\u5236\u5e76\u6309\u6bcf\u884c 16 \u4e2a\u5b57\u8282\u7684\u683c\u5f0f\u8f93\u51fa\uff08\u6587\u672c\uff09<\/li>\n<\/ol>\n
      \u5176\u4ed6<\/h2>\n
        \n
      1. \u534f\u7a0b\u548c await<\/code><\/li>\n<\/ol>\n
        https:\/\/segmentfault.com\/a\/1190000042918986<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
        B\u7ad9\u89c6\u9891\uff1ahttps:\/\/www.bilibili.com\/vide… \u8bed\u6cd5\u5c42\u9762 \u53ef\u7a7a\u5bf9\u8c61\uff08\u548c C […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10006931","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10006931","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10006931"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10006931\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10006931"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10006931"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10006931"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}