这段代码怎么能不那么丑陋 - V2EX
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qwertyegg
V2EX    Java

这段代码怎么能不那么丑陋

  •  
  •   qwertyegg Dec 28, 2018 5225 views
    This topic created in 2678 days ago, the information mentioned may be changed or developed.
    public static void main(String[] args){
    List<String> languages = Arrays.asList("Java", "Scala", "C++", "Haskell", "Lisp");
    filter(languages, (str)->((String)str).length() > 4);
    }

    static void filter(List<String> names, Predicate condition) {
    for(String name: names) {
    if(condition.test(name)) {
    System.out.println(name + " ");
    }
    }
    }


    第 3 行里面的 Lambda 表达式,如果不做强制转换似乎 str 会被认为是个 Object 而不是 String。可是这个强制转换太丑了,有没有优雅的处理方法?

    update:

    知道问题了, filer 方法里面应该给 Predicate 指定类型,改成这样
    static void filter(List<String> names, Predicate<String> condition) {
    for(String name: names) {
    if(condition.test(name)) {
    System.out.println(name + " ");
    }
    }
    }
    13 replies    2018-12-28 16:49:03 +08:00
    liuhuansir
        1
    liuhuansir  
       Dec 28, 2018 via iPhone
    filter 需要自己实现么?很久没写 Java 了,jdk 里没有么?难怪说 Java 语言嗦
    lhx2008
        2
    lhx2008  
       Dec 28, 2018 via Android
    @liuhuansir 不用,只是楼主搞的不知道啥玩意
    lhx2008
        3
    lhx2008  
       Dec 28, 2018 via Android   1
    languages.stream().filter(str->str.length>4).forEach(System.out::println);
    yxlaisj
        4
    yxlaisj  
       Dec 28, 2018 via Android
    也许楼主用的是 java7
    liaojl
        5
    liaojl  
       Dec 28, 2018 via Android
    你都知道 lambda 了,竟然不知道 stream 吗。。。
    anthow
        6
    anthow  
       Dec 28, 2018
    @yxlaisj 7 没有 Predicate 吧
    Tsukihime
        7
    Tsukihime  
       Dec 28, 2018
    languages.stream().filter(x -> x.length() > 4).forEach(System.out::println);
    Tsukihime
        8
    Tsukihime  
       Dec 28, 2018
    @zydxn 啊 没注意 3#发过了
    sagaxu
        9
    sagaxu  
       Dec 28, 2018 via Android
    val languages = arrayOf("Java", "Scala", "C++", "Haskell", "Lisp")
    languages.filter{it.length>4}.forEach(println)

    Kotlin 欢迎你
    Marstin
        10
    Marstin  
       Dec 28, 2018
    在为什么不用 markdown
    wleexi
        11
    wleexi  
       Dec 28, 2018
    @Marstin 同感。甚至发个 gayhub 的外链都好啊。。
    dfourc
        12
    dfourc  
       Dec 28, 2018
    @Marstin 看着辣眼睛啊
    geying
        13
    geying  
       Dec 28, 2018
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