{"id":1173,"date":"2016-08-18T17:37:28","date_gmt":"2016-08-18T09:37:28","guid":{"rendered":"http:\/\/www.yeetrack.com\/?p=1173"},"modified":"2016-08-18T23:02:17","modified_gmt":"2016-08-18T15:02:17","slug":"%e8%b5%b0%e8%bf%91guava%e4%ba%8c-%e5%87%bd%e6%95%b0%e5%bc%8f%e7%bc%96%e7%a8%8b","status":"publish","type":"post","link":"https:\/\/www.yeetrack.com\/?p=1173","title":{"rendered":"\u8d70\u8fd1Guava(\u4e8c): \u51fd\u6570\u5f0f\u7f16\u7a0b"},"content":{"rendered":"
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\u51fd\u6570\u5f0f\u7f16\u7a0b\uff1a<\/h1>\n

\u4f7f\u7528Function\u63a5\u53e3(jdk8\u4e2d\u5df2\u7ecf\u5b58\u5728)\uff1a<\/h2>\n
\/**\n * \u5176\u529f\u80fd\u5c31\u662f\u5c06\u8f93\u5165\u7c7b\u578b\u8f6c\u6362\u4e3a\u8f93\u51fa\u7c7b\u578b\n *\/\npublic interface Function<F, T> {\n  T apply(@Nullable F input);\n}<\/code><\/pre>\n
\u6bd4\u5982\u4e00\u4e2a\u7b80\u5355\u7684\u65e5\u671f\u8f6c\u6362\uff1a<\/p>\n
\/**\n * \u65e5\u671f\u8f6c\u6362\n *\/\npublic class DateFormatFunction implements Function<Date, String> {\n\t@Override\n\tpublic String apply(Date input) {\n\t\tSimpleDateFormat dateFormat = new SimpleDateFormat(\"dd\/mm\/yyyy\");\n\t\treturn dateFormat.format(input);\n\t}\n}<\/code><\/pre>\n
\u4f7f\u7528Functions\u7c7b\uff1a<\/h2>\n
    \n
  • Functions.forMap()<\/span>\u65b9\u6cd5\uff1a<\/span><\/li>\n<\/ul>\n
    \/**\n * \u5dde\u7c7b\n *\/\npublic class State {\n\tprivate String name;\n\tprivate String code;\n\tprivate Set<City> mainCities = new HashSet<City>();\n}<\/code><\/pre>\n
    \u73b0\u5728\u4f60\u60f3\u5728\u4e00\u4e2aMap<String, State>(key\u4e3a\u5dde\u7684\u7f16\u53f7)\u5bf9\u8c61\u4e2d\u67e5\u627e\u67d0\u4e2akey, \u4f60\u53ef\u4ee5\uff1a<\/p>\n
    Map<String, State> states = new HashMap<String, State>();\nFunction<String, State> lookup = Functions.forMap(states);\nSystem.out.println(lookup.apply(key));\/\/key\u4e0d\u5b58\u5728\u4f1a\u629b\u5f02\u5e38\n\n\/\/\u4f60\u4e5f\u53ef\u4ee5\u7ed9\u4e0d\u5b58\u5728\u7684key\u6307\u5b9a\u4e00\u4e2a\u9ed8\u8ba4\u503c\nFunction<String, State> lookup = Functions.forMap(states, null);<\/code><\/pre>\n
      \n
    • Functions.compose()<\/span>\u65b9\u6cd5<\/span><\/li>\n<\/ul>\n
      \/**\u57ce\u5e02\u7c7b**\/\npublic class City {\n\tprivate String name;\n\tprivate String zipCode;\n\tprivate int population;\n\n\t@Override\n\tpublic String toString() {\n\t\treturn name;\n\t}\n}<\/code><\/pre>\n
      \/**\n * \u5c06\u5dde\u7684\u57ce\u5e02\u8f6c\u6362\u4e3a\u5b57\u7b26\u4e32\n *\/\npublic class StateToCityString implements Function<State, String> {\n\t@Override\n\tpublic String apply(State input) {\n\t\treturn Joiner.on(\",\").join(input.getMainCities());\n\t}\n}<\/code><\/pre>\n
      \u4f60\u53ef\u4ee5\u901a\u8fc7\u7ec4\u5408Function\uff0c\u67e5\u627e\u67d0\u5dde\u7684\u57ce\u5e02\u5217\u8868<\/p>\n
      Function<String, State> lookup = Functions.forMap(states);\nFunction<State, String> stateFunction = new StateToCityString(); \/\/\u5dde\u5230\u57ce\u5e02\u7684\u8f6c\u6362\nFunction<String, String> stateCitiesFunction = Functions.compose(stateFunction, lookup); \/\/\u7ec4\u5408Function\nSystem.out.println(stateCitiesFunction.apply(key));<\/code><\/pre>\n
      \u7b49\u4ef7\u4e8e\uff1a<\/p>\n
      stateFunction.apply(lookup.apply(key));<\/code><\/pre>\n
      \u4f7f\u7528Predicate\u63a5\u53e3(jdk8\u4e2d\u5df2\u5b58\u5728)\uff1a<\/h2>\n
        \n
      • Predicate\u63a5\u53e3<\/span><\/li>\n<\/ul>\n
        public interface Predicate<T> {\n     boolean apply(T input); \/\/\u4e0d\u540c\u4e8eFunction.apply, \u8be5apply\u7528\u4e8e\u8fc7\u6ee4\u5bf9\u8c61\n}<\/code><\/pre>\n
        \u5982\uff1a<\/p>\n
        \/**\n * \u8fc7\u6ee4\u4eba\u53e3\u5c0f\u4e8e500000\u7684\u57ce\u5e02\n *\/\npublic class PopulationPredicate implements Predicate<City> {\n\t@Override\n\tpublic boolean apply(City input) {\n\t\treturn input.getPopulation() <= 500000;\n\t}\n}<\/code><\/pre>\n
        \u4f7f\u7528Predicates\u7c7b\uff1a<\/h3>\n
        \u6709\u4e24\u4e2a\u8fc7\u6ee4\u6761\u4ef6\uff1a<\/p>\n
        \/**\n * \u9009\u62e9\u6c14\u5019\u4e3aTEMPERATE\u7684\u57ce\u5e02\n *\/\npublic class TemperateClimatePredicate implements Predicate<City> {\n\t@Override\n\tpublic boolean apply(City input) {\n\t\treturn input.getClimate().equals(Climate.TEMPERATE);\n\t}\n}\n\n\/**\n * \u9009\u62e9\u96e8\u91cf\u5c0f\u4e8e45.7\u7684\u57ce\u5e02\n *\/\npublic class LowRainfallPredicate implements Predicate<City> {\n\t@Override\n\tpublic boolean apply(City input) {\n\t\treturn input.getAverageRainfall() < 45.7;\n\t}\n}<\/code><\/pre>\n
        \u4f60\u53ef\u4ee5\u8fd0\u7528\u4e0b\u9762\u7684\u65b9\u6cd5\u5b9e\u73b0\u8fc7\u6ee4\u7ec4\u5408\u7b49\uff1a<\/p>\n
        Predicates.and(smallPopulationPredicate,lowRainFallPredicate);\/\/\u4e14\nPredicates.or(smallPopulationPredicate,temperateClimatePredicate);\/\/\u6216\nPredicate.not(smallPopulationPredicate);\/\/\u975e\nPredicates.compose(smallPopulationPredicate,lookup);\/\/\u7ec4\u5408\u8f6c\u6362\u518d\u8fc7\u6ee4<\/code><\/pre>\n
        \u4f7f\u7528Supplier\u63a5\u53e3\uff1a<\/h2>\n
          \n
        • Supplier\u63a5\u53e3<\/span><\/li>\n<\/ul>\n
          public interface Supplier<T> {\n       T get(); \/\/\u7528\u4e8e\u521b\u5efa\u5bf9\u8c61\n}<\/code><\/pre>\n
          \u4f7f\u7528Suppliers\u7c7b\uff1a<\/h2>\n
            \n
          • Suppliers.memorize()<\/span>\u65b9\u6cd5\uff1a<\/span><\/li>\n<\/ul>\n
            SupplyCity sc = new SupplyCity();\nSystem.out.println(Suppliers.memoize(sc).get());\nSystem.out.println(Suppliers.memoize(sc).get());\/\/\u8fd4\u56de\u540c\u4e00\u5bf9\u8c61, \u5355\u4f8b<\/code><\/pre>\n
              \n
            • Suppliers.memorizeWithExpiration()<\/span>\u65b9\u6cd5\uff1a<\/span><\/li>\n<\/ul>\n
              SupplyCity sc = new SupplyCity(); \/\/\u8d85\u65f6\u518d\u65b0\u5efa\u5bf9\u8c61, \u7c7b\u4f3c\u7f13\u5b58\nSupplier<City> supplier = Suppliers.memoizeWithExpiration(sc, 5, TimeUnit.SECONDS);\nCity c = supplier.get();\nSystem.out.println(c); \nThread.sleep(3000);\nc = supplier.get();\nSystem.out.println(c); \/\/\u4e0e\u4e4b\u524d\u76f8\u7b49\nThread.sleep(2000);\nc = supplier.get();\nSystem.out.println(c); \/\/\u4e0e\u4e4b\u524d\u4e0d\u7b49<\/code><\/pre>\n
              Guava\u51fd\u6570\u5f0f\u7f16\u7a0b\u57fa\u7840\uff0c\u540e\u9762\u96c6\u5408\u5904\u7406\u4e2d\uff0c\u5c06\u4f53\u73b0\u5f97\u66f4\u5f3a\u5927\u3002<\/p>\n
              \n
              \u8d70\u8fd1Guava(\u4e00): \u57fa\u672c\u5de5\u5177<\/a><\/p><\/blockquote>\n