{"id":3975,"date":"2018-06-10T07:21:55","date_gmt":"2018-06-09T23:21:55","guid":{"rendered":"https:\/\/ixyzero.com\/blog\/?p=3975"},"modified":"2018-06-10T07:21:55","modified_gmt":"2018-06-09T23:21:55","slug":"java%e4%b8%ad%e7%9a%84%e4%b8%80%e4%ba%9b%e5%9f%ba%e7%a1%80%e4%bb%a3%e7%a0%81%e7%89%87%e6%ae%b5_2","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/3975.html","title":{"rendered":"Java\u4e2d\u7684\u4e00\u4e9b\u57fa\u7840\u4ee3\u7801\u7247\u6bb5_2"},"content":{"rendered":"<p>=Start=<\/p>\n<h4 id=\"id-\u6a21\u677f-\u7f18\u7531\uff1a\">\u7f18\u7531\uff1a<\/h4>\n<p>\u5728\u5b66\u4e60Java\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u65ad\u7528\u6587\u7ae0\u8fdb\u884c\u6574\u7406\u603b\u7ed3\uff08\u5e38\u7528\u529f\u80fd\u7684Java\u5b9e\u73b0\uff09\uff0c\u4e89\u53d6\u65e9\u65e5\u80fd\u8f83\u4e3a\u719f\u7ec3\u7684\u4f7f\u7528Java\u8fdb\u884c\u5f00\u53d1\u3002<\/p>\n<h4 id=\"id-\u6a21\u677f-\u6b63\u6587\uff1a\">\u6b63\u6587\uff1a<\/h4>\n<h5 id=\"id-\u6a21\u677f-\u53c2\u8003\u89e3\u7b54\uff1a\">\u53c2\u8003\u89e3\u7b54\uff1a<\/h5>\n<h6><strong>1. Java\u4e2d\u5982\u4f55\u5c06 Long \u578b\u8f6c\u6362\u6210 int\/Integer \u578b<\/strong><\/h6>\n<p><span style=\"color: #ff0000;\">Java\u4e2dInteger\u5c5e\u4e8e\u4e0d\u53ef\u66f4\u6539\u7c7b\u578b\uff0c\u800c\u4e14Long\u548cInteger\u6ca1\u6709\u4efb\u4f55\u7ee7\u627f\u5173\u7cfb\uff0c\u6240\u4ee5\u4e0d\u80fd\u76f4\u63a5\u8f6c\u6362\u3002<\/span>\u5426\u5219\u4f1a\u62a5\u9519\u300cjava.lang.Long cannot be cast to java.lang.Integer\u300d<\/p>\n<p><span style=\"color: #ff0000;\"><strong>\u6ce8\uff1ajava.lang.Number \u662f Integer,Long \u7684\u7236\u7c7b\u3002<\/strong><\/span><\/p>\n<pre class=\"lang:default decode:true\">\/\/ \u7b80\u5355\u7c7b\u578b\u7684\u8f6c\u6362\u53ef\u4ee5\u76f4\u63a5\u8fdb\u884c\r\nlong l = 100000;\r\nint i = (int) l;\r\n\r\n\/\/ Long\u578b\u53d8\u91cf\u7684\u8f6c\u6362\u5c31\u4e0d\u80fd\u76f4\u63a5\u8fdb\u884c\u4e86\r\nLong x = 100L;\r\nint y = x.intValue();<\/pre>\n<ul>\n<li><a href=\"https:\/\/blog.csdn.net\/leejeff\/article\/details\/77802835\">java.lang.Long cannot be cast to java.lang.Integer\u89e3\u51b3\u529e\u6cd5<\/a><\/li>\n<li><a href=\"https:\/\/stackoverflow.com\/questions\/4355303\/how-can-i-convert-a-long-to-int-in-java\">https:\/\/stackoverflow.com\/questions\/4355303\/how-can-i-convert-a-long-to-int-in-java<\/a><\/li>\n<li><a href=\"https:\/\/www.cnblogs.com\/li-yongjie\/p\/5387445.html\">\u5bf9\u4e8ejfinal\u4e2djava.lang.Long cannot be cast to java.lang.Integer\u7684\u89e3\u51b3\u65b9\u6cd5<\/a><\/li>\n<\/ul>\n<h6><strong>2. Java\u4e2d\u5b57\u7b26\u4e32\u7684\u5e38\u7528\u64cd\u4f5c<\/strong><\/h6>\n<ul>\n<li><a href=\"http:\/\/www.runoob.com\/java\/java-string.html\">http:\/\/www.runoob.com\/java\/java-string.html<\/a><\/li>\n<\/ul>\n<pre class=\"lang:default decode:true\">\/\/ \u5b57\u7b26\u67e5\u627e &amp; \u5b57\u7b26\u4e32\u67e5\u627e\r\nstr.indexOf()\r\n\r\n\/\/ \u5b57\u7b26\u4e32\u622a\u53d6\r\nstr.substring()\r\n\r\n\/\/ \u5b57\u7b26\u4e32\u5207\u5206\r\nstr.split()<\/pre>\n<ul>\n<li><a href=\"http:\/\/www.runoob.com\/java\/java-stringbuffer.html\">Java StringBuffer \u548c StringBuilder \u7c7b<\/a><\/li>\n<\/ul>\n<blockquote><p>\u5f53\u5bf9\u5b57\u7b26\u4e32\u8fdb\u884c\u4fee\u6539\u7684\u64cd\u4f5c\u8f83\u591a\u7684\u65f6\u5019\uff0c\u9700\u8981\u4f7f\u7528 StringBuffer \u548c StringBuilder \u7c7b\u3002\u56e0\u4e3a<span style=\"color: #ff0000;\"><strong>\u548c\u5e38\u89c4\u7684 String \u7c7b\u4e0d\u540c\u7684\u662f\uff0cStringBuffer \u548c StringBuilder \u7c7b\u7684\u5bf9\u8c61\u80fd\u591f\u88ab\u591a\u6b21\u7684\u4fee\u6539\uff0c\u5e76\u4e14\u4e0d\u4ea7\u751f\u65b0\u7684\u672a\u4f7f\u7528\u5bf9\u8c61\u3002<\/strong><\/span><\/p>\n<p>StringBuilder \u7c7b\u5728 Java 5 \u4e2d\u88ab\u63d0\u51fa\uff0c\u5b83\u548c StringBuffer \u4e4b\u95f4\u7684\u6700\u5927\u4e0d\u540c\u5728\u4e8e StringBuilder \u7684\u65b9\u6cd5\u4e0d\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff08\u4e0d\u80fd\u540c\u6b65\u8bbf\u95ee\uff09\u3002<\/p>\n<p><span style=\"color: #ff0000;\"><strong>\u7531\u4e8e StringBuilder \u76f8\u8f83\u4e8e StringBuffer \u6709\u901f\u5ea6\u4f18\u52bf\uff0c\u6240\u4ee5\u591a\u6570\u60c5\u51b5\u4e0b\u5efa\u8bae\u4f7f\u7528 StringBuilder \u7c7b\u3002\u7136\u800c\u5728\u5e94\u7528\u7a0b\u5e8f\u8981\u6c42\u7ebf\u7a0b\u5b89\u5168\u7684\u60c5\u51b5\u4e0b\uff0c\u5219\u5fc5\u987b\u4f7f\u7528 StringBuffer \u7c7b\u3002<\/strong><\/span><\/p><\/blockquote>\n<h6><strong>3. \u7279\u6b8a\u4e00\u70b9\u7684\u5b57\u7b26\u4e32\u5207\u5206<\/strong><\/h6>\n<p>\u501f\u52a9\uff1a<br \/>\nimport com.google.common.base.Splitter;<br \/>\n\u5b9e\u73b0 <span style=\"color: #ff0000;\"><strong>\u5728\u5207\u5206\u65f6\uff0c\u81ea\u52a8\u53bb\u6389\u7a7a\u503c\u00a0<\/strong><\/span>\u7684\u529f\u80fd\u3002<\/p>\n<pre class=\"lang:default decode:true\">package com.ixyzero.learn.misc;\r\n\r\nimport com.google.common.base.Splitter;\r\n\r\nimport java.util.List;\r\n\r\npublic class TestStringUtils {\r\n    public static void main(String[] args) {\r\n        String testInput = \"1,2,,4,,6\";\r\n        String[] arrResult = testInput.split(\",\"); \/\/ [1, 2, '', 4, '', 6]\r\n        System.out.println(arrResult.length); \/\/ 6\r\n        for (int i=0; i&lt;arrResult.length; i++) {\r\n            System.out.println(Integer.valueOf(i) + \"]=&gt;\\t\" + arrResult[i]);\r\n        }\r\n        System.out.println();\r\n\r\n        Splitter splitter = Splitter.on(\",\").trimResults();\r\n        List&lt;String&gt; valueList = null;\r\n        valueList = splitter.omitEmptyStrings().splitToList(testInput);\r\n        System.out.println(valueList);\t\/\/ [1, 2, 4, 6]\r\n        System.out.println(valueList.size());\t\/\/ 4\r\n        for (int i=0; i&lt;valueList.size(); i++) {\r\n            System.out.println(Integer.valueOf(i) + \"]=&gt;\\t\" + valueList.get(i));\r\n        }\r\n    }\r\n}<\/pre>\n<h6><strong>4. Java\u4e2d\u65e5\u671f\u5b57\u7b26\u4e32\u683c\u5f0f\u7684\u6821\u9a8c<\/strong><\/h6>\n<ul>\n<li><a href=\"https:\/\/blog.csdn.net\/sunroyi666\/article\/details\/78048747\">Java\u65e5\u671f\u683c\u5f0fCheck<\/a><\/li>\n<li><a href=\"http:\/\/www.runoob.com\/java\/java-date-time.html\">Java \u65e5\u671f\u65f6\u95f4<\/a><\/li>\n<li><a href=\"https:\/\/www.cnblogs.com\/loveyakamoz\/archive\/2011\/08\/18\/2145047.html\">java\u65e5\u671f\u683c\u5f0f\u5927\u5168 format SimpleDateFormat<\/a><\/li>\n<li><a href=\"https:\/\/blog.csdn.net\/qq_27093465\/article\/details\/53034427\">java \u65e5\u671f\u683c\u5f0f\u5316&#8211; SimpleDateFormat \u7684\u4f7f\u7528\u3002\u5b57\u7b26\u4e32\u8f6c\u65e5\u671f\uff0c\u65e5\u671f\u8f6c\u5b57\u7b26\u4e32<\/a><\/li>\n<\/ul>\n<pre class=\"lang:default decode:true\">package com.ixyzero.learn.misc;\r\n\r\nimport java.text.SimpleDateFormat;\r\nimport java.util.Date;\r\n\r\npublic class TestValidDateStr {\r\n    public static boolean isValidDate(String s, String pattern) {\r\n        SimpleDateFormat sdf = new SimpleDateFormat(pattern);\r\n        if(s == null || s.trim().equals(\"\") || pattern == null || pattern.trim().equals(\"\")){\r\n            return false;\r\n        }\r\n        try {\r\n            return sdf.format(sdf.parse(s)).equals(s);\r\n        } catch (Exception e) {\r\n            return false;\r\n        }\r\n    }\r\n\r\n    public static void main(String[] args) {\r\n        System.out.println(isValidDate(\"\", \"yyyy-MM\")); \/\/ false\r\n        System.out.println(isValidDate(\"2018-06\", \"yyyy-MM\"));  \/\/ true\r\n        System.out.println(isValidDate(\"2018-06-09\", \"yyyy-MM\"));   \/\/ false\r\n        System.out.println(isValidDate(\"2018-06-09\", \"\"));   \/\/ false\r\n        System.out.println(isValidDate(\"2018-06-09 11:01\", \"yyyy-MM-dd HH:mm\"));   \/\/ true\r\n\r\n        SimpleDateFormat sdf = new SimpleDateFormat(\"yyyy-MM-dd HH:mm\");\r\n        System.out.println(sdf.format(new Date()));\r\n    }\r\n\r\n}<\/pre>\n<h6><strong>5. Java\u4e2d\u6253\u5370 \u6570\u7ec4 \u76843\u79cd\u65b9\u6cd5\u603b\u7ed3<\/strong><\/h6>\n<ul>\n<li><a href=\"http:\/\/www.runoob.com\/java\/java-array.html\">http:\/\/www.runoob.com\/java\/java-array.html<\/a><\/li>\n<li><a id=\"cb_post_title_url\" href=\"https:\/\/www.cnblogs.com\/hebao0514\/p\/5575065.html\">Java\u57fa\u7840\u77e5\u8bc6\u5f3a\u5316105\uff1a\u6253\u5370\u6570\u7ec4\u7684\u65b9\u6cd5\u603b\u7ed3<\/a><\/li>\n<\/ul>\n<pre class=\"lang:default decode:true\">package com.ixyzero.learn.misc;\r\n\r\npublic class TestArray {\r\n    public static void main(String[] args) {\r\n        double[] myList = {1.9, 2.9, 3.4, 3.5};\r\n\r\n        \/\/ \u6253\u5370\u6240\u6709\u6570\u7ec4\u5143\u7d20\uff08\u5e38\u89c4 for \u5faa\u73af\u2014\u2014\u6839\u636e\u6570\u7ec4\u4e0b\u6807\u8fdb\u884c\u904d\u5386\uff09\r\n        for (int i = 0; i &lt; myList.length; i++) {\r\n           System.out.println(myList[i]);\r\n        }\r\n\r\n        \/\/ \u6253\u5370\u6240\u6709\u6570\u7ec4\u5143\u7d20\uff08foreach \u5faa\u73af\uff09\r\n        for (double element: myList) {\r\n           System.out.println(element);\r\n        }\r\n\r\n        \/**\r\n         * \u4f7f\u7528 Arrays.toString \u8f93\u51fa\u6570\u7ec4\u5185\u5bb9\r\n         *\/\r\n        System.out.println(Arrays.toString(myList));\r\n    }\r\n}<\/pre>\n<h6><strong>6. Java\u4e2d\u6253\u5370 map \u7684\u65b9\u6cd5\u603b\u7ed3<\/strong><\/h6>\n<ul>\n<li><a href=\"https:\/\/stackoverflow.com\/questions\/8119366\/sorting-hashmap-by-values\/13913206#13913206\">https:\/\/stackoverflow.com\/questions\/8119366\/sorting-hashmap-by-values\/13913206#13913206<\/a><\/li>\n<\/ul>\n<pre class=\"lang:default decode:true \">package com.ixyzero.learn.misc;\r\n\r\nimport java.util.*;\r\nimport java.util.Map.Entry;\r\n\r\n\/**\r\n * https:\/\/stackoverflow.com\/questions\/8119366\/sorting-hashmap-by-values\/13913206#13913206\r\n *\/\r\npublic class TestPrintMap\r\n{\r\n    public static void main(String[] args) {\r\n\r\n        \/\/ Creating dummy unsorted map\r\n        Map&lt;String, Integer&gt; unsortedMap = new HashMap&lt;&gt;();\r\n        unsortedMap.put(\"B\", 55);\r\n        unsortedMap.put(\"A\", 80);\r\n        unsortedMap.put(\"D\", 20);\r\n        unsortedMap.put(\"C\", 70);\r\n\r\n        System.out.println(\"Before sorting......\");\r\n        printMap(unsortedMap);\r\n    }\r\n\r\n    public static void printMap(Map&lt;String, Integer&gt; map)\r\n    {\r\n        for (Entry&lt;String, Integer&gt; entry : map.entrySet()) {\r\n            System.out.println(\"Key: \" + entry.getKey() + \"\\tValue: \"+ entry.getValue());\r\n        }\r\n    }\r\n}<\/pre>\n<p>&amp;<\/p>\n<pre class=\"lang:default decode:true \">import java.util.*;\r\n\r\npublic class TestPrint {\r\n    public static void main(String[] args) {\r\n    Map&lt;String, String&gt; map = new HashMap&lt;String, String&gt;();\r\n    map.put(\"1\", \"value1\");\r\n    map.put(\"2\", \"value2\");\r\n    map.put(\"3\", \"value3\");\r\n\r\n    \/\/\u7b2c\u4e00\u79cd\uff1a\u666e\u904d\u4f7f\u7528\uff0c\u4e8c\u6b21\u53d6\u503c\r\n    System.out.println(\"\u901a\u8fc7Map.keySet\u904d\u5386key\u548cvalue\uff1a\");\r\n    for (String key : map.keySet()) {\r\n      System.out.println(\"key= \"+ key + \" and value= \" + map.get(key));\r\n    }\r\n\r\n    \/\/\u7b2c\u4e8c\u79cd\r\n    System.out.println(\"\u901a\u8fc7Map.entrySet\u4f7f\u7528iterator\u904d\u5386key\u548cvalue\uff1a\");\r\n    Iterator&lt;Map.Entry&lt;String, String&gt;&gt; it = map.entrySet().iterator();\r\n    while (it.hasNext()) {\r\n      Map.Entry&lt;String, String&gt; entry = it.next();\r\n      System.out.println(\"key= \" + entry.getKey() + \" and value= \" + entry.getValue());\r\n    }\r\n\r\n    \/\/\u7b2c\u4e09\u79cd\uff1a\u63a8\u8350\uff0c\u5c24\u5176\u662f\u5bb9\u91cf\u5927\u65f6\r\n    System.out.println(\"\u901a\u8fc7Map.entrySet\u904d\u5386key\u548cvalue\");\r\n    for (Map.Entry&lt;String, String&gt; entry : map.entrySet()) {\r\n      System.out.println(\"key= \" + entry.getKey() + \" and value= \" + entry.getValue());\r\n    }\r\n\r\n    \/\/\u7b2c\u56db\u79cd\r\n    System.out.println(\"\u901a\u8fc7Map.values()\u904d\u5386\u6240\u6709\u7684value\uff0c\u4f46\u4e0d\u80fd\u904d\u5386key\");\r\n    for (String v : map.values()) {\r\n      System.out.println(\"value= \" + v);\r\n    }\r\n\r\n}<\/pre>\n<p>\u9664\u4e86\u8fd9\u79cd\u6307\u5b9aMap\u7c7b\u578b\u7684\u65b9\u5f0f\u4e4b\u5916\uff0c\u8fd8\u53ef\u4ee5\u8003\u8651\u501f\u52a9\u4e00\u4e0b<a href=\"http:\/\/www.runoob.com\/java\/java-generics.html\">\u6cdb\u578b<\/a>\uff08\u5728map\u5143\u7d20\u4e0d\u662f\u7279\u522b\u591a\u7684\u60c5\u51b5\u4e0b\uff09\u6765\u5b9e\u73b0\u3002<\/p>\n<h5 id=\"id-\u6a21\u677f-\u53c2\u8003\u94fe\u63a5\uff1a\">\u53c2\u8003\u94fe\u63a5\uff1a<\/h5>\n<ul>\n<li>\u5982\u4e0a<\/li>\n<\/ul>\n<p>=END=<\/p>\n","protected":false},"excerpt":{"rendered":"<p>=Start= \u7f18\u7531\uff1a \u5728\u5b66\u4e60Java\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u65ad\u7528\u6587\u7ae0\u8fdb\u884c\u6574\u7406\u603b\u7ed3\uff08\u5e38\u7528\u529f\u80fd\u7684Java\u5b9e\u73b0\uff09\uff0c\u4e89\u53d6\u65e9\u65e5\u80fd\u8f83\u4e3a [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,7],"tags":[930,61,561],"class_list":["post-3975","post","type-post","status-publish","format-standard","hentry","category-knowledgebase-2","category-programing","tag-code","tag-java","tag-snippet"],"views":8263,"_links":{"self":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3975","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/comments?post=3975"}],"version-history":[{"count":1,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3975\/revisions"}],"predecessor-version":[{"id":3976,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3975\/revisions\/3976"}],"wp:attachment":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/media?parent=3975"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/categories?post=3975"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/tags?post=3975"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}