{"id":1171,"date":"2016-08-18T17:35:32","date_gmt":"2016-08-18T09:35:32","guid":{"rendered":"http:\/\/www.yeetrack.com\/?p=1171"},"modified":"2016-08-18T23:03:54","modified_gmt":"2016-08-18T15:03:54","slug":"%e8%b5%b0%e8%bf%91guava%e4%b8%80-%e5%9f%ba%e6%9c%ac%e5%b7%a5%e5%85%b7","status":"publish","type":"post","link":"https:\/\/www.yeetrack.com\/?p=1171","title":{"rendered":"\u8d70\u8fd1Guava(\u4e00): \u57fa\u672c\u5de5\u5177"},"content":{"rendered":"
\n
\n

\u57fa\u672c\u5de5\u5177\uff1a<\/h1>\n

\u4f7f\u7528Joiner\u7c7b\uff1a<\/h2>\n
    \n
  • \u4f8b\u5982\u6211\u4eec\u60f3\u5c06\u5b57\u7b26\u4e32\u5217\u8868\u901a\u8fc7\u4e00\u4e2a\u5206\u9694\u7b26\u94fe\u63a5\u8d77\u6765\uff0c\u4ee5\u524d\u7684\u65b9\u5f0f\u5c31\u662f\u8fed\u4ee3<\/span>\uff0cappend<\/span>\u7b49\u64cd\u4f5c\uff0c\u4f7f\u7528Joiner\u53ef\u4ee5\u66f4\u65b9\u4fbf\u3002<\/span><\/li>\n<\/ul>\n
      \n
    • Joiner\u4e00\u65e6\u521b\u5efa\u4e0d\u53ef\u53d8\uff0c\u7b26\u5408\u4e0d\u53d8\u6027<\/span>\uff0c\u56e0\u6b64\u7ebf\u7a0b\u5b89\u5168<\/span>\u3002<\/span><\/li>\n<\/ul>\n

      \u770b\u4e00\u4e9b\u6d4b\u8bd5\u7528\u4f8b\uff1a<\/p>\n

        \n
      • \u94fe\u63a5\u5b57\u7b26\u4e32\u5217\u8868<\/span>\uff1a<\/span><\/li>\n<\/ul>\n
        String delimiter = \",\";\n\/\/ Joiner\u7c7b\u4e00\u65e6\u521b\u5efa\u5219\u4e0d\u53ef\u53d8\uff0c\u6ee1\u8db3\u4e0d\u53ef\u53d8\u6027\uff0c\u56e0\u6b64\u7ebf\u7a0b\u5b89\u5168\nJoiner joiner = Joiner.on(delimiter);\n\t\t\n\/\/ \u5ffd\u7565null\nString excludeNullString = joiner.skipNulls().join(langs);\n\/\/ \u5c06null\u66ff\u4ee3\u4e3aempty\u5b57\u7b26\u4e32\nString replaceNullString = joiner.useForNull(\"empty\").join(langs);\nSystem.out.println(\"excludeNullString: \" + excludeNullString);\nSystem.out.println(\"replaceNullString: \" + replaceNullString);\n\t\t\n\/\/ \u4e0d\u5bf9null\u5904\u7406\uff0c\u9ed8\u8ba4\u4f1a\u629bNullPointerException\nString defaultNullString = joiner.join(langs); \/\/langs\u4e3aList<String>\nSystem.out.println(\"defaultNullString: \" + defaultNullString);<\/code><\/pre>\n
          \n
        • \u94fe\u63a5\u591a\u4e2a\u5b57\u7b26\u4e32<\/span>\uff1a<\/span><\/li>\n<\/ul>\n
          String delimiter = \",\";\n\/\/ Joiner\u7c7b\u4e00\u65e6\u521b\u5efa\u5219\u4e0d\u53ef\u53d8\uff0c\u6ee1\u8db3\u4e0d\u53ef\u53d8\u6027\uff0c\u56e0\u6b64\u7ebf\u7a0b\u5b89\u5168\nJoiner joiner = Joiner.on(delimiter).skipNulls();\n\/\/joiner.useForNull(\"empty\"); \/\/\u91cd\u590d\u5b9a\u4e49null\u64cd\u4f5c\u4f1a\u629b\u5f02\u5e38\nString res = joiner.join(null, \"foo\",\"bar\");\nSystem.out.println(res); \/\/foo,bar<\/code><\/pre>\n
            \n
          • appendTo<\/span>\u5230\u5b9e\u73b0\u4e86Appendable<\/span>\u63a5\u53e3\u7684\u7c7b\u4e2d\uff1a<\/span><\/li>\n<\/ul>\n
            \/\/append\u5230StringBuilder\nStringBuilder stringBuilder = new StringBuilder();\nJoiner joiner = Joiner.on(\",\").skipNulls();\njoiner.appendTo(stringBuilder, \"appendTo\", \"StringBuilder\");\nSystem.out.println(stringBuilder); \/\/appendTo,StringBuilder\n\t\t\n\/\/append\u5230\u8f93\u51fa\u6d41\nFileWriter writer = new FileWriter(\"append_text.txt\");\njoiner.appendTo(writer, \"appendTo\", \"FileWriter\");\nwriter.close();<\/code><\/pre>\n
              \n
            • \u901a\u8fc7MapJoiner<\/span>\u94fe\u63a5Map\u5bf9\u8c61\uff1a<\/span><\/li>\n<\/ul>\n
              Map<String, String> map = new HashMap<>();\nmap.put(\"key1\", \"value1\");\nmap.put(\"key2\", \"value2\");\nmap.put(\"key3\", \"value3\");\nMapJoiner mapJoiner = Joiner.on(\",\").withKeyValueSeparator(\"=\");\nString str = mapJoiner.join(map);\nSystem.out.println(str);\/\/\u7ed3\u679c\u5982:key3=value3,key2=value2,key1=value1<\/code><\/pre>\n
              \u4f7f\u7528Splitter\u7c7b\uff1a<\/h2>\n
                \n
              • Splitter\u529f\u80fd\u4e0eJoiner\u76f8\u53cd\uff0c\u5176\u5bf9\u5b57\u7b26\u4e32\u8fdb\u884c\u5206\u5272\u64cd\u4f5c<\/span>\u3002<\/span><\/li>\n<\/ul>\n
                  \n
                • \u5206\u5272\u5b57\u7b26\u4e32\uff0c\u8fd4\u56deIterable<String>\u5bf9\u8c61\uff1a<\/li>\n<\/ul>\n
                  String str = \"try ,do , your , best\";\nSplitter splitter = Splitter.on(\",\").trimResults(); \/\/\u7528\u9017\u53f7\u5206\u5272\u4e14\u53bb\u6389\u6bcf\u4e2a\u5b57\u7b26\u4e32\u5468\u56f4\u7684\u7a7a\u683c\n\/\/splitter.trimResults(); \/\/\u8fd9\u6837\u662f\u4e0d\u4f1a\u53bb\u6389\u5404\u4e2a\u5143\u7d20\u7a7a\u683c\u7684, \u5b83\u4ec5\u8fd4\u56de\u4e00\u4e2a\u65b0\u7684Splitter\nIterable<String> res = splitter.split(str);\nSystem.out.println(res); \/\/[try, do, your, best]<\/code><\/pre>\n
                    \n
                  • \u4f7f\u7528MapSplitter\u5206\u5272\u5b57\u7b26\u4e32\uff0c\u8fd4\u56deMap<String, String>\u5bf9\u8c61\uff1a<\/span><\/li>\n<\/ul>\n
                    String str = \"key3=value3,key2=value2,key1=value1\";\nMapSplitter splitter = Splitter.on(\",\").withKeyValueSeparator(\"=\");\nMap<String, String> map = splitter.split(str);\nSystem.out.println(map);\/\/ {key3=value3, key2=value2, key1=value1}<\/code><\/pre>\n
                    \u4f7f\u7528Strings\u7c7b\uff1a<\/h2>\n
                      \n
                    • Strings\u7c7b\u6709\u7528\u7684API:<\/span><\/li>\n<\/ul>\n
                      \/\/\u7528padChar\u586b\u5145string\u540e\u9762, \u4f7fstring\u6700\u5c0f\u957f\u5ea6\u4e3aminLength\npadEnd(String string, int minLength, char padChar)\n\/\/\u7528padChar\u586b\u5145string\u524d\u9762, \u4f7fstring\u6700\u5c0f\u957f\u5ea6\u4e3aminLength\npadStart(String string, int minLength, char padChar)\n\/\/null\u8f6c\u6362\u4e3a\"\"\nnullToEmpty(String string)\n\/\/\"\"\u8f6c\u6362\u4e3anull\nemptyToNull(String string)\n\/\/true, \u5982\u679c\u5b57\u7b26\u4e32\u4e3anull\u6216\u8005\"\"\nisNullOrEmpty(Strng string)<\/code><\/pre>\n
                      \u4f7f\u7528CharMatcher\u7c7b\uff1a<\/h2>\n
                        \n
                      • \u66ff\u6362\u591a\u4e2a\u8fde\u7eed\u7684\u7a7a\u683c\u4e3a\u5355\u4e2a\u7a7a\u683c<\/span>\u3002<\/span><\/li>\n<\/ul>\n
                        String tabsAndSpaces = \"String  with      spaces     and tabs\";\n\/\/\u5c06\u591a\u4e2a\u8fde\u7eed\u7684\u7a7a\u683c\u66ff\u6362\u4e3a\u4e00\u4e2a\nString scrubbed = CharMatcher.WHITESPACE.collapseFrom(tabsAndSpaces,' ');\nSystem.out.println(scrubbed); \/\/String with spaces and tabs<\/code><\/pre>\n
                          \n
                        • \u6709\u65f6\u6211\u4eec\u8fd8\u60f3\u5c06\u5934\u5c3e\u7684\u7a7a\u683c\u53bb\u6389<\/span>\uff1a<\/span><\/li>\n<\/ul>\n
                          String tabsAndSpaces = \"    String  with     spaces     and tabs\";\nString scrubbed = CharMatcher.WHITESPACE.trimAndCollapseFrom(tabsAndSpaces, ' ');\nSystem.out.println(scrubbed); \/\/String with spaces and tabs<\/code><\/pre>\n
                            \n
                          • \u4fdd\u7559\u5236\u5b9a\u5b57\u7b26\uff0c\u5982\u6570\u5b57\uff0c\u5b57\u6bcd\u7b49\uff1a<\/span><\/li>\n<\/ul>\n
                            String lettersAndNumbers = \"foo989yxbar234\";\nString retained = CharMatcher.JAVA_DIGIT.retainFrom(lettersAndNumbers); \/\/\u4fdd\u7559\u6570\u5b57\nSystem.out.println(retained); \/\/989234<\/code><\/pre>\n
                              \n
                            • \u4f60\u4e5f\u53ef\u4ee5\u901a\u8fc7Or\u7ec4\u5408\u591a\u4e2aCharMatcher:<\/span><\/li>\n<\/ul>\n
                              CharMatcher cm = CharMatcher.JAVA_DIGIT.or(CharMatcher.WHITESPACE);\nString retained = cm.retainFrom(\"foo9 89y xbar 234\");\/\/\u4fdd\u7559\u6570\u5b57\u548c\u7a7a\u683c\nSystem.out.println(retained); \/\/9 89  234<\/code><\/pre>\n
                              \u4f7f\u7528Preconditions\u7c7b\uff1a<\/h2>\n
                                \n
                              • \u8fd9\u662f\u4e00\u4e2a\u7528\u4e8e\u5224\u65ad\u6761\u4ef6\u7684\u4e00\u4e2a\u5de5\u5177\uff0c\u7c7b\u4f3cjunit\u4e2dAseert\u529f\u80fd\u3002<\/span><\/li>\n<\/ul>\n
                                checkNotNull(obj, \"\u68c0\u67e5\u5bf9\u8c61\u4e0d\u80fd\u4e3a\u7a7a\");\ncheckElementIndex(index, arr.length,\"\u68c0\u67e5\u6570\u7ec4\u7d22\u5f15\");\ncheckArgument(valueToSet <= 100, \"\u68c0\u67e5\u53c2\u6570\u503c\");\ncheckState(validateObjectState(), \"\u68c0\u67e5\u5bf9\u8c61\u72b6\u6001\");<\/code><\/pre>\n
                                \u4f7f\u7528Objects\u7c7b\uff1a<\/h2>\n
                                  \n
                                • toString\u65b9\u6cd5\u7684\u4f7f\u7528\u3002<\/span><\/li>\n<\/ul>\n
                                  public class Book implements Comparable<Book> {\n\tprivate Person author;\n\tprivate String title;\n\tprivate String publisher;\n\tprivate String isbn;\n\tprivate double price;\n\t...\n\t@Override\n\tpublic int compareTo(Book o) { \n\t\t return ComparisonChain.start() \/\/\u94fe\u5f0f\u6bd4\u8f83,\u5728\u7b2c\u4e00\u4e2a\u975e0\u5904\u8fd4\u56de\n                 .compare(this.title, o.getTitle())\n                 .compare(this.author, o.getAuthor())\n                 .compare(this.publisher, o.getPublisher())\n                 .compare(this.isbn, o.getIsbn())\n                 .compare(this.price, o.getPrice())\n                 .result();\n\t}\n\t\n\t@Override\n\tpublic int hashCode(){\n\t\treturn Objects.hashCode(title, author, publisher, isbn);\/\/hashCode\u751f\u6210\n\t}\n\n\t@Override\n\tpublic String toString() {\n\t\treturn Objects.toStringHelper(this) \/\/toString\n                .omitNullValues() \/\/\u5ffd\u7565null\u5c5e\u6027\n                .add(\"title\", title)\n                .add(\"author\", author)\n                .add(\"publisher\", publisher)\n                .add(\"price\",price)\n                .add(\"isbn\", isbn).toString();\n\t}\n}<\/code><\/pre>\n
                                    \n
                                  • \u83b7\u53d6\u975enull\u9ed8\u8ba4\u503c<\/span><\/li>\n<\/ul>\n
                                    String str = null;\nstr = Objects.firstNonNull(str, \"defaut value\");\nSystem.out.println(str);<\/code><\/pre>\n
                                    \u4ee5\u4e0a\u5c31\u662f\u57fa\u672c\u5de5\u5177\u4f7f\u7528\u3002<\/span><\/p>\n<\/div>\n
                                    \n
                                    \u8d70\u8fd1Guava(\u4e00): \u57fa\u672c\u5de5\u5177<\/a><\/p><\/blockquote>\n