{"id":875,"date":"2022-04-07T14:31:33","date_gmt":"2022-04-07T06:31:33","guid":{"rendered":"https:\/\/axinyi.xuenixiang.com\/?p=875"},"modified":"2022-04-07T14:31:57","modified_gmt":"2022-04-07T06:31:57","slug":"javase-7","status":"publish","type":"post","link":"https:\/\/axinyi.xuenixiang.com\/index.php\/2022\/04\/07\/javase-7\/","title":{"rendered":"JavaSE-\u7b2c\u4e03\u7ae0"},"content":{"rendered":"\n<h1>\u7b2c\u4e03\u7ae0 \u5e38\u7528\u7c7b<\/h1>\n\n\n\n<h2>7.1 String<\/h2>\n\n\n\n<h3>7.1.1 String\u7c7b\u662f\u4e0d\u53ef\u53d8\u7c7b<\/h3>\n\n\n\n<ul><li>\u5c31\u662fstring\u5bf9\u8c61\u521b\u5efa\u540e\u4e0d\u53ef\u4ee5\u4fee\u6539<\/li><li>\u6848\u4f8b\uff1a<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    public static void main(String&#91;] args) {\n        String s1 = \"a\";\n        String s2 = \"b\";\n        s1 = s1 +s2;\n        System.out.println(s1);\n    }\n}<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"861\" height=\"413\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247.png\" alt=\"\" class=\"wp-image-876\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247.png 861w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-300x144.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-768x368.png 768w\" sizes=\"(max-width: 861px) 100vw, 861px\" \/><\/figure>\n\n\n\n<ul><li>\u4ece\u4e0a\u9762\u56fe\u53ef\u4ee5\u770b\u5230string\u5bf9\u8c61\u8d4b\u503c\u540e\u4e0d\u80fd\u518d\u4fee\u6539\u4e86\uff0c\u8fd9\u5c31\u662f\u4e0d\u53ef\u53d8\u5bf9\u8c61\uff0c\u5982\u679c\u5bf9\u5b57\u7b26\u4e32\u4fee\u6539\uff0c\u90a3\u4e48\u5c06\u4f1a\u521b\u5efa\u65b0\u7684\u5bf9\u8c61\u3002<\/li><li>\u6ce8\u610f\uff1a\u53ea\u8981\u4f7f\u7528\u53cc\u5f15\u53f7\u8d4b\u503c\u7684\u5b57\u7b26\u4e32\uff0c\u90a3\u4e48\u5728\u7f16\u8bd1\u671f\u5c06\u4f1a\u653e\u5230\u65b9\u6cd5\u533a\u7684\u5e38\u91cf\u6c60\u4e2d\uff0c\u5982\u679c\u662f\u8fd0\u884c\u65f6\u5bf9\u5b57\u7b26\u4e32\u62fc\u63a5\u90a3\u4e48\u4f1a\u653e\u5230\u5806\u533a\u4e2d<\/li><li>\u5e38\u91cf\u6c60\u4e2d\u4e0d\u5141\u8bb8\u51fa\u73b0\u91cd\u590d\u7684\u5bf9\u8c61<\/li><\/ul>\n\n\n\n<h3>7.1.2 String s1 = new String(\"abc\");<\/h3>\n\n\n\n<ul><li>\u521b\u5efa\u4e862\u4e2a\u5bf9\u8c61\uff0c\u5206\u522b\u5728\u5806\u548c\u5e38\u91cf\u6c60\uff0c\u8fd4\u56de\u5806\u4e2d\u7684\u5730\u5740<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    public static void main(String&#91;] args) {\n        \n        \/**\n         \u5728\u5806\u4e2d\u5fc5\u987b\u521b\u5efa\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5e76\u4e14\u8fd4\u56de\u7684\u5730\u5740\u5c31\u662f\u5806\u4e2d\u5bf9\u8c61\u7684\u5730\u5740\uff0c\n         \u4f46\u662f\uff0c\u5e38\u91cf\u6c60\u4e5f\u4f1a\u521b\u5efa\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5982\u679c\u5e38\u91cf\u6c60\u4e2d\u5df2\u7ecf\u5b58\u5728\u4e86abc\u5bf9\u8c61\uff0c\u90a3\u4e48\uff0c\u5c31\u4e0d\u518d\u521b\u5efa\u4e86\n         *\/\n\n        String s2 = new String(\"abc\");\n\n    }\n}<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"825\" height=\"432\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-1.png\" alt=\"\" class=\"wp-image-877\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-1.png 825w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-1-300x157.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-1-768x402.png 768w\" sizes=\"(max-width: 825px) 100vw, 825px\" \/><\/figure>\n\n\n\n<h3>7.1.3 \u4e00\u5171\u521b\u5efa\u4e863\u4e2a\u5bf9\u8c61<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    public static void main(String&#91;] args) {\n        String s1 = \"abc\";\n        String s2 = new String(\"abc\");\n        String s3 = new String(\"abc\");\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u5806\u4e2d\u521b\u5efa\u4e862\u4e2a\u5bf9\u8c61\uff0c\u5e38\u91cf\u6c60\u4e2d\u521b\u5efa\u4e861\u4e2a\u5bf9\u8c61<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"828\" height=\"422\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-2.png\" alt=\"\" class=\"wp-image-878\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-2.png 828w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-2-300x153.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-2-768x391.png 768w\" sizes=\"(max-width: 828px) 100vw, 828px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"491\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-3-1024x491.png\" alt=\"\" class=\"wp-image-879\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-3-1024x491.png 1024w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-3-300x144.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-3-768x368.png 768w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-3.png 1300w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h2>7.2 String\u7684\u5e38\u7528\u65b9\u6cd5<\/h2>\n\n\n\n<h3>7.2.1 \u4f7f\u7528\u6d4b\u8bd5\u65b9\u6cd5\uff1a\u5355\u5143\u6d4b\u8bd5junit<\/h3>\n\n\n\n<ul><li>\u521b\u5efa\u6e90\u7801\u6d4b\u8bd5\u5305<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"784\" height=\"244\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-4.png\" alt=\"\" class=\"wp-image-880\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-4.png 784w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-4-300x93.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-4-768x239.png 768w\" sizes=\"(max-width: 784px) 100vw, 784px\" \/><\/figure>\n\n\n\n<ul><li>\u7f16\u5199\u6d4b\u8bd5\u65b9\u6cd5<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    \/\/\u7f16\u5199\u4e00\u4e2a\u65b9\u6cd5\n    public int sum(int i,int n){\n        return i+n+1;\n    }\n}<\/code><\/pre>\n\n\n\n<pre class=\"wp-block-code\"><code>import com.Demo;\nimport junit.framework.TestCase;\n\npublic class DemoTest extends TestCase {\n\n    \/\/\u6d4b\u8bd5\u65b9\u6cd5\n    public void test1(){\n        Demo demo = new Demo();\n        int sum = demo.sum(1,1);\n        System.out.println(sum);\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u53ef\u4ee5\u4f7f\u7528<strong>\u65ad\u8a00<\/strong>\u8fdb\u884c\u903b\u8f91\u6d4b\u8bd5<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"748\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-5-1024x748.png\" alt=\"\" class=\"wp-image-881\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-5-1024x748.png 1024w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-5-300x219.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-5-768x561.png 768w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-5.png 1250w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h3>7.2.2 \u5b57\u7b26\u4e32\u5e38\u7528\u65b9\u6cd5<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import junit.framework.TestCase;\n\npublic class DemoTest extends TestCase {\n\n    \/\/toCharArray\uff1a\u628a\u5b57\u7b26\u4e32\u8f6c\u4e3a\u5b57\u7b26\u6570\u7ec4\n    public void test1(){\n        String s1 = \"abc\";\n        \/\/\u8f6c\u4e3a\u6570\u7ec4\n        char&#91;] array = s1.toCharArray();\n        \/\/\u5faa\u73af\n        for (int i = 0; i &lt; array.length; i++) {\n            System.out.println(array&#91;i]);\n        }\n    }\n\n    \/\/charAt\u65b9\u6cd5\uff1a\u6839\u636e\u5b57\u7b26\u7d22\u5f15\u8fd4\u56de\n    public void test2(){\n        String s = \"abc\";\n        char c = s.charAt(1);\n        System.out.println(c);\n    }\n\n    \/\/codePointAt\u8fd4\u56de\u5bf9\u5e94\u5b57\u7b26\u7684unicode\u7801\n    public void test3(){\n        String s = \"abc\";\n        int i = s.codePointAt(0);\n        System.out.println(i);\n    }\n\n    \/\/concat\u62fc\u63a5\u5b57\u7b26\u4e32\n    public void test4() {\n        String s = \"abc\";\n        System.out.println(s + \"hello\");\n        \/\/\u4f7f\u7528\u65b9\u6cd5\n        System.out.println(s.concat(\"java\"));\n    }\n\n    \/\/contains\u662f\u5426\u5305\u542b\u6307\u5b9a\u7684\u5b57\u7b26\u4e32\n    public void test5(){\n        String s = \"abc\";\n        System.out.println(s.contains(\"ab\"));\n        System.out.println(s.contains(\"cd\"));\n    }\n\n    \/\/endsWith\u5224\u65ad\u5b57\u7b26\u4e32\u662f\u5426\u542b\u6709\u6307\u5b9a\u7684\u540e\u7f00\n    public void test6() {\n        String s = \"abc\";\n        System.out.println(s.endsWith(\"c\"));\n        System.out.println(s.endsWith(\"abc\"));\n        System.out.println(s.endsWith(\"bc\"));\n    }\n\n    \/\/startsWith\u5224\u65ad\u5b57\u7b26\u4e32\u662f\u5426\u542b\u6709\u6307\u5b9a\u7684\u524d\u7f00\n    public void test7(){\n        String s = \"abc\";\n        System.out.println(s.startsWith(\"c\"));\n        System.out.println(s.startsWith(\"abc\"));\n        System.out.println(s.startsWith(\"bc\"));\n    }\n    \n    \/\/equalsIgnoreCase\u6bd4\u8f83\u503c\u65f6\u4e0d\u533a\u5206\u5927\u5c0f\u5199\n    public void test8(){\n        String s1 = \"abc\";\n        String s2 = \"ABC\";\n\n        System.out.println(s1.equals(s2));\n        System.out.println(s1.equalsIgnoreCase(s2));\n        \/\/\u539f\u7406\n        System.out.println(s1.toLowerCase().equals(s2.toLowerCase()));\n    }\n\n\n    \/\/getBytes() \u8f6c\u4e3a\u5b57\u8282\u6570\u7ec4\n    public void test9(){\n        String s1 = \"abc\";\n        byte&#91;] bytes = s1.getBytes();\n            for (int i = 0; i &lt; bytes.length;i++) {\n                System.out.println(bytes&#91;i]);\n            }\n    }\n\n    \/\/hashCode\u83b7\u53d6\u54c8\u5e0c\u7801\n    public void test10(){\n        String s1 = \"abc\";\n        System.out.println(s1.hashCode());\n    }\n\n    \/\/indexOf\u83b7\u53d6\u6307\u5b9a\u5b57\u7b26\u6216\u5b57\u7b26\u4e32\u7b2c\u4e00\u6b21\u51fa\u73b0\u7684\u4f4d\u7f6e(\u4e0b\u6807)\n    public void test11(){\n        String s1 = \"hello\";\n        System.out.println(s1.indexOf(\"l\"));\n    }\n\n    \/\/lastIndexOf\u83b7\u53d6\u6307\u5b9a\u5b57\u7b26\u6216\u5b57\u7b26\u4e32\u6700\u540e\u4e00\u6b21\u51fa\u73b0\u7684\u4f4d\u7f6e(\u4e0b\u6807)\n    public void test12(){\n        String s1 = \"hello\";\n        System.out.println(s1.lastIndexOf(\"l\"));\n    }\n\n    \/\/\u53ef\u4ee5\u83b7\u53d6\u6587\u4ef6\u7684\u6269\u5c55\u540d\u79f0\n    public void test13(){\n        String s1 = \"java.txt\";\n        System.out.println(s1.lastIndexOf(\".\"));\n    }\n\n    \/\/subString\u622a\u53d6\u5b57\u7b26\u4e32\n    public void test14(){\n        String s1 = \"java.txt\";\n        \/\/\u4fee\u6539\u6587\u4ef6\u540d\u79f0\n        int index = s1.lastIndexOf(\".\");\n        \/\/\u622a\u53d6\n        String name = s1.substring(index);\n        \/\/\u65b0\u540d\u79f0\n        name = UUID.randomUUID()+name;\n        System.out.println(name);\n    }\n\n    \/\/subString\u622a\u53d6\u5b57\u7b26\u4e32\n    public void test15(){\n        String s1 = \"hadoop\";\n        \/\/\u5de6\u95ed\u53f3\u5f00\n        System.out.println(s1.substring(1,3));\n    }\n\n    \/\/isEmpty() \u662f\u5426\u4e3a\u7a7a\n    public void test16(){\n        String s1 = \"hadoop\";\n        System.out.println(s1.isEmpty());\n    }\n\n    \/\/jion\u62fc\u63a5\n    public void test17(){\n        \/\/\u7b2c\u4e00\u4e2a\u53c2\u6570\u8868\u793a\u5206\u9694\u7b26\u53f7\n        String str = String.join(\";\",\"a\",\"b\",\"c\");\n        System.out.println(str);\n    }\n\n    \/\/length()\u83b7\u53d6\u5b57\u7b26\u4e32\u957f\u5ea6\u7684\u65b9\u6cd5\n    public void test18(){\n        String s = \"abc\";\n        System.out.println(s.length());\n    }\n\n    \/\/replace\u66ff\u6362\n    public void test19(){\n        String s = \"aaa111ggggg666666sssssss77777\";\n        String replace = s.replace(\"7\", \"\");\n        System.out.println(replace);\n    }\n\n    public void test20(){\n        String uuid = UUID.randomUUID().toString();\n        System.out.println(uuid);\n        System.out.println(uuid.replace(\"-\",\"\"));\n    }\n\n    \/\/replaceAll\u66ff\u6362\uff1a\u53ef\u4ee5\u4f7f\u7528\u6b63\u5219\u8868\u8fbe\u5f0f\n    public void test21(){\n        String s = \"aaa111ggggg666666sssssss77777\";\n        \/\/System.out.println(s.replace(\"77777\",\"\u597d\"));\n        System.out.println(s.replaceAll(\"7{5}\",\"\u597d\"));\n    }\n\n    public void test22(){\/\/\u5c06\u6570\u5b57\u66ff\u6362\u4e3a\u597d\n        String s = \"aaa111ggggg666666sssssss77777\";\n        System.out.println(s.replaceAll(\"\\\\d\",\"\u597d\"));\n    }\n\n    public void test23(){\/\/\u5c06\u975e\u6570\u5b57\u66ff\u6362\u4e3a\u597d\n        String s = \"aaa111ggggg666666sssssss77777\";\n        System.out.println(s.replaceAll(\"\\\\D\",\"\u597d\"));\n    }\n\n    \/\/split\u6309\u7167\u6307\u5b9a\u5206\u9694\u7b26\u53f7\u8fd4\u56de\u5b57\u7b26\u4e32\u6570\u7ec4\n    public void test24(){\n        String s = \"hello;java;hbase;hive;flink\";\n        String&#91;] array = s.split(\";\");\n        for (int index = 0; index &lt; array.length; index++) {\n            System.out.println(array&#91;index]);\n        }\n    }\n\n    public void test25(){\/\/\u53ef\u4ee5\u4f7f\u7528\u6b63\u5219\u8868\u8fbe\u5f0f\n        String s = \"hello;java,hbase.hive:flink\";\n        String&#91;] array = s.split(\"\\\\W\");\n        for (int index = 0; index &lt; array.length; index++) {\n            System.out.println(array&#91;index]);\n        }\n    }\n\n    \/\/toUpperCase\u8f6c\u4e3a\u5927\u5c0f\u5199\n    public void test26(){\/\/\u53ef\u4ee5\u4f7f\u7528\u6b63\u5219\u8868\u8fbe\u5f0f\n        String s = \"hello\";\n        System.out.println(s.toUpperCase());\n\n        String s1 = \"ABC\";\n        System.out.println(s1.toLowerCase());\n    }\n\n    \/\/toString\u8f6c\u4e3a\u5b57\u7b26\u4e32\n    public void test27(){\n        UUID uuid = UUID.randomUUID();\n        \/\/\u8f6c\u5b57\u7b26\u4e32\n        System.out.println(uuid.toString());\n    }\n\n    \/\/valueOf\u8f6c\u4e3a\u5b57\u7b26\u4e32\n    public void test28(){\n        int n = 1000;\n        String s = String.valueOf(n);\n        System.out.println(s);\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.3 StringBuffer\u548cStringBuilder<\/h2>\n\n\n\n<h3>7.3.1 StringBuffer<\/h3>\n\n\n\n<ul><li>StringBuffer\u548cStringBuilder\u79f0\u4e3a\u5b57\u7b26\u4e32\u7f13\u51b2\u533a\uff1b\u539f\u7406\uff1a\u9884\u5148\u7533\u8bf7\u4e00\u5757\u5185\u5b58\u5b58\u50a8\u5b57\u7b26\u5e8f\u5217\uff0c\u5982\u679c\u5b58\u6ee1\u4e86\uff0c\u4f1a\u91cd\u65b0\u6539\u53d8\u7f13\u51b2\u533a\u7684\u5927\u5c0f\uff0c\u4ee5\u5bb9\u7eb3\u66f4\u591a\u7684\u5b57\u7b26\u4e32\u3002<\/li><li>StringBuffer\u662f\u53ef\u53d8\u5bf9\u8c61\uff0cString\u662f\u4e0d\u53ef\u53d8\u5bf9\u8c61\uff0c\u8fd9\u662f\u5b83\u4eec\u6700\u5927\u7684\u533a\u522b<\/li><li>\u4ee5\u540e\u5728\u62fc\u63a5\u5b57\u7b26\u4e32\u65f6\u5c31\u4e0d\u80fd\u4f7f\u7528string\u800c\u662f\u4f7f\u7528StringBuffer\u6216StringBuilder<\/li><\/ul>\n\n\n\n<h3>7.3.2 \u4e0d\u80fd\u8fd9\u6837\u62fc\u63a5\u5b57\u7b26\u4e32<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        String str = \"\";\n        for (int i = 0; i &lt; 10; i++) {\n            \/\/\u8fd9\u79cd\u62fc\u63a5\u5b57\u7b26\u4e32\u7684\u65b9\u5f0f\u4f1a\u4ea7\u751f\u5927\u91cf\u5783\u573e\u5bf9\u8c61\n            str += i;\n        }\n        System.out.println(str);\n    }\n}<\/code><\/pre>\n\n\n\n<h3>7.3.3 \u63a8\u8350\u4f7f\u7528StringBuilder\u62fc\u63a5\u5b57\u7b26\u4e32<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        StringBuilder sb = new StringBuilder();\n        for (int i = 0; i &lt; 10; i++) {\n            \/\/\u63a8\u8350\u4f7f\u7528\n            sb.append(i);\n        }\n        System.out.println(sb);\n    }\n}<\/code><\/pre>\n\n\n\n<h3>7.3.4 StringBuffer\u533a\u522bStringBuilder<\/h3>\n\n\n\n<h4>7.3.4.1 StringBuffer<\/h4>\n\n\n\n<ul><li>\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u5c31\u662f\u591a\u7ebf\u7a0b\u7684<\/li><li>\u6548\u7387\u6bd4\u8f83\u4f4e<\/li><li>\u6e90\u4ee3\u7801<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"785\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-6-1024x785.png\" alt=\"\" class=\"wp-image-882\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-6-1024x785.png 1024w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-6-300x230.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-6-768x589.png 768w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-6.png 1187w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h4>7.3.4.2 StringBuilder<\/h4>\n\n\n\n<ul><li>\u5355\u7ebf\u7a0b,\u53ef\u4ee5\u4f7f\u7528\u5728\u65b9\u6cd5\u4e2d\uff0c\u4f7f\u4e4b\u6210\u4e3a\u5c40\u90e8\u53d8\u91cf\u5c31\u5b89\u5168\u4e86(\u6808\u5e27\u95f4\u4e0d\u901a\u4fe1)<\/li><li>\u6267\u884c\u6548\u7387\u9ad8<\/li><li>\u6e90\u4ee3\u7801<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"997\" height=\"682\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-7.png\" alt=\"\" class=\"wp-image-883\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-7.png 997w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-7-300x205.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-7-768x525.png 768w\" sizes=\"(max-width: 997px) 100vw, 997px\" \/><\/figure>\n\n\n\n<h3>7.3.5 StringBuffer\u6e90\u4ee3\u7801<\/h3>\n\n\n\n<ul><li>\u521d\u59cb\u5316\u7684\u957f\u5ea6\uff1a16\u4e2a\u5b57\u7b26<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"943\" height=\"184\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-8.png\" alt=\"\" class=\"wp-image-884\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-8.png 943w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-8-300x59.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-8-768x150.png 768w\" sizes=\"(max-width: 943px) 100vw, 943px\" \/><\/figure>\n\n\n\n<ul><li>\u6269\u5bb9\u7684\u5bb9\u91cf<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"375\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-9-1024x375.png\" alt=\"\" class=\"wp-image-885\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-9-1024x375.png 1024w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-9-300x110.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-9-768x281.png 768w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-9.png 1347w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<ul><li>\u6700\u5927\u7684\u5bb9\u91cf<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"943\" height=\"163\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-10.png\" alt=\"\" class=\"wp-image-886\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-10.png 943w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-10-300x52.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-10-768x133.png 768w\" sizes=\"(max-width: 943px) 100vw, 943px\" \/><\/figure>\n\n\n\n<h4>7.3.5.1 \u7b14\u8bd5\u9898<\/h4>\n\n\n\n<ul><li>StringBuilder stringBuilder = new StringBuilder(20);\u6269\u5bb9\u4e86\u51e0\u6b21\uff1f<\/li><\/ul>\n\n\n\n<p>\u7b54\uff1a\u6269\u5bb9\u4e860\u6b21<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"946\" height=\"414\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-11.png\" alt=\"\" class=\"wp-image-887\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-11.png 946w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-11-300x131.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-11-768x336.png 768w\" sizes=\"(max-width: 946px) 100vw, 946px\" \/><\/figure>\n\n\n\n<h3>7.3.6 StringBuilder\u4e2d\u7684\u5e38\u7528\u65b9\u6cd5<\/h3>\n\n\n\n<ul><li>\u4f7f\u7528deleteCharAt<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        StringBuilder sb = new StringBuilder();\n        \/\/\u62fc\u63a5\u6570\u5b57\n        for (int i = 0; i &lt; 10; i++) {\n            sb.append(i).append(\",\");\n        }\n        \u53bb\u6389\u6700\u540e\u4e00\u4e2a\u9017\u53f7\n\t\tsb.deleteCharAt(sb.toString().length()-1);\n        System.out.println(sb);\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u5b57\u7b26\u4e32\u622a\u53d6<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        StringBuilder sb = new StringBuilder();\n        \/\/\u62fc\u63a5\u6570\u5b57\n        for (int i = 0; i &lt; 10; i++) {\n            sb.append(i).append(\",\");\n        }\n        \/\/\u53bb\u6389\u6700\u540e\u4e00\u4e2a\u9017\u53f7\n        \/\/\u4f7f\u7528\u5b57\u7b26\u4e32\u622a\u53d6\n        String str = sb.toString();\n        String substring = str.substring(0, str.length() - 1);\n        System.out.println(substring);\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u5728\u4ee3\u7801\u4e2d\u53bb\u6389<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        StringBuilder sb = new StringBuilder();\n        \/\/\u62fc\u63a5\u6570\u5b57\n        for (int i = 0; i &lt; 10; i++) {\n            sb.append(i);\n            \/\/\u5224\u65ad\n            if (i!=9) {\n                sb.append(\",\");\n            }\n        }\n        System.out.println(sb);\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u7b14\u8bd5\u9898\uff1a\u628a\u5b57\u7b26\u4e32\u9006\u5e8f\u8f93\u51fa\uff1f<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        String str = \"hadoop\";\n        StringBuilder sb = new StringBuilder(str);\n        \/\/\u8c03\u7528\u65b9\u6cd5\n        StringBuilder reverse = sb.reverse();\n        System.out.println(reverse);\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.4 \u57fa\u672c\u7c7b\u578b\u5bf9\u5e94\u7684\u5305\u88c5\u7c7b\u578b<\/h2>\n\n\n\n<h3>7.4.1 \u5305\u88c5\u7c7b\u578b\u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u5b9e\u7528\u65b9\u6cd5<\/h3>\n\n\n\n<ul><li>\u7c7b\u578b\u8f6c\u6362<\/li><li>\u5305\u88c5\u7c7b\u578b\u90fd\u662ffinal\u4fee\u9970\u7684<\/li><li>\u90fd\u662f\u4e0d\u53ef\u53d8\u5bf9\u8c61<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>\u57fa\u672c\u7c7b\u578b<\/th><th>\u5305\u88c5\u7c7b\u578b<\/th><\/tr><\/thead><tbody><tr><td>byte<\/td><td>Byte<\/td><\/tr><tr><td>short<\/td><td>Short<\/td><\/tr><tr><td>int<\/td><td><strong>Integer<\/strong><\/td><\/tr><tr><td>long<\/td><td>Long<\/td><\/tr><tr><td>float<\/td><td>Float<\/td><\/tr><tr><td>double<\/td><td>Double<\/td><\/tr><tr><td>char<\/td><td><strong>Character<\/strong><\/td><\/tr><tr><td>boolean<\/td><td>Boolean<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3>7.4.2 \u7c7b\u5c42\u6b21\u7ed3\u6784<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"317\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-12-1024x317.png\" alt=\"\" class=\"wp-image-888\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-12-1024x317.png 1024w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-12-300x93.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-12-768x238.png 768w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-12.png 1458w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h4>7.4.2.1 \u7c7b\u578b\u8f6c\u6362\u7684\u65b9\u6cd5<\/h4>\n\n\n\n<ul><li>\u9664Boolean\u548cCharacter\u4ee5\u5916\uff0c\u5176\u5b83\u5305\u88c5\u7c7b\u90fd\u6709\u8f6c\u4e3a\u5305\u88c5\u7c7b\u578b\u548c\u57fa\u672c\u7c7b\u578b\u7684\u65b9\u6cd5<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        String str = \"100\";\n        \/\/\u8f6c\u4e3a\u5305\u88c5\u7c7b\u578b\n        Integer integer = Integer.valueOf(str);\n        \/\/\u8f6c\u4e3a\u57fa\u672c\u7c7b\u578b\n        int i = Integer.parseInt(str);\n    }\n}<\/code><\/pre>\n\n\n\n<h4>7.4.2.2 \u81ea\u52a8\u62c6\u88c5\u7bb1<\/h4>\n\n\n\n<ul><li>\u81ea\u52a8\u5c06\u57fa\u672c\u7c7b\u578b\u8f6c\u4e3a\u5bf9\u8c61--\u88c5\u7bb1<\/li><li>\u81ea\u52a8\u5c06\u5bf9\u8c61\u8f6c\u4e3a\u57fa\u672c\u7c7b\u578b--\u62c6\u7bb1<\/li><li>\u7b14\u8bd5\u9898<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class DemoTest {\n\n    @Test\n    public void test1(){\n        \/\/\u53d6\u503c\u7684\u8303\u56f4\u662f\u6309\u7167byte\u7684\u8303\u56f4\u83b7\u53d6\u7684\n        Integer i = 128;\n        Integer n = 128;\n        \/\/\u8fd4\u56defalse\n        System.out.println(i == n);\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.5 \u65e5\u671f\u7c7b<\/h2>\n\n\n\n<h3>7.5.1 \u4f20\u7edf\u65b9\u5f0f<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import org.junit.Test;\n\nimport java.text.SimpleDateFormat;\nimport java.util.Date;\n\npublic class DemoTest {\n\n    @Test\n    public void test1(){\n        \/\/\u4f20\u7edf\u7684\u65e5\u671f\u7c7b\u5df2\u7ecf\u4e0d\u5efa\u8bae\u4f7f\u7528\uff0c\u56e0\u4e3a\uff0c\u6548\u7387\u4f4e\n        Date date = new Date();\n        System.out.println(date);\n        \/\/\u8bbe\u7f6e\u65e5\u671f\u683c\u5f0f:HH\u8868\u793a24\u5c0f\u65f6\u5236\uff1bhh\u8868\u793a12\u5c0f\u65f6\u5236\n        SimpleDateFormat sdf = new SimpleDateFormat(\"yyyy-MM-dd HH:mm:ss\");\n        System.out.println(sdf.format(date));\n    }\n}<\/code><\/pre>\n\n\n\n<h3>7.5.2 \u4f7f\u7528\u65b0\u7684\u65e5\u671f\u7c7b<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import org.junit.Test;\nimport java.time.LocalDate;\nimport java.time.LocalDateTime;\nimport java.time.LocalTime;\nimport java.time.format.DateTimeFormatter;\n\n\npublic class DemoTest {\n\n    @Test\n    public void test1(){\n        \/\/\u83b7\u53d6\u65e5\u671f\n        LocalDate date = LocalDate.now();\n        System.out.println(date);\n        \/\/\u83b7\u53d6\u65f6\u95f4\n        LocalTime time = LocalTime.now();\n        System.out.println(time);\n    }\n\n    @Test\n    public void test2(){\n        \/\/\u83b7\u53d6\u65e5\u671f\u65f6\u95f4\n        LocalDateTime dateTime = LocalDateTime.now();\n        System.out.println(dateTime);\n    }\n\n    @Test\n    public void test3(){\n        \/\/\u83b7\u53d6\u65e5\u671f\u65f6\u95f4:\u4f7f\u7528\u6807\u51c6\u683c\u5f0f\u5316\n        DateTimeFormatter formatter = DateTimeFormatter.ISO_LOCAL_DATE_TIME;\n        LocalDateTime dateTime = LocalDateTime.now();\n        \/\/\u683c\u5f0f\u5316\n        System.out.println(formatter.format(dateTime));\n    }\n\n    @Test\n    public void test4(){\n        \/\/\u83b7\u53d6\u65e5\u671f\u65f6\u95f4:\u4f7f\u7528\u81ea\u5b9a\u4e49\u683c\u5f0f\u5316\n        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(\"yyyy-MM-dd HH:mm:ss\");\n        LocalDateTime dateTime = LocalDateTime.now();\n        \/\/\u683c\u5f0f\u5316\n        System.out.println(formatter.format(dateTime));\n    }\n}<\/code><\/pre>\n\n\n\n<h3>7.5.3 \u6dfb\u52a0\u65f6\u95f4<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import org.junit.Test;\nimport java.time.LocalDateTime;\n\npublic class DemoTest {\n\n    @Test\n    public void test1(){\n        \/\/\u6307\u5b9a\u65e5\u671f\u65f6\u95f4\n        LocalDateTime dateTime = LocalDateTime.of(2022, 02, 11, 12, 25);\n        System.out.println(dateTime);\n    }\n\n    @Test\n    public void test2(){\n        \/\/\u6dfb\u52a0\u5e74\u3001\u6708\u3001\u65e5...\n        LocalDateTime dateTime = LocalDateTime.now();\n        LocalDateTime plusDays = dateTime.plusDays();\n        System.out.println(plusDays);\n    }\n}<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" width=\"970\" height=\"526\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-13.png\" alt=\"\" class=\"wp-image-889\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-13.png 970w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-13-300x163.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-13-768x416.png 768w\" sizes=\"(max-width: 970px) 100vw, 970px\" \/><\/figure>\n\n\n\n<h3>7.5.4 \u51cf\u5c11\u65f6\u95f4<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import org.junit.Test;\nimport java.time.LocalDateTime;\nimport java.time.format.DateTimeFormatter;\n\n\npublic class DemoTest {\n\n    @Test\n    public void test1(){\n        \/\/\u51cf\u5c11\u5e74\u3001\u6708\u3001\u65e5...\n        LocalDateTime dateTime = LocalDateTime.now();\n        LocalDateTime minusDays = dateTime.minusDays(3);\n        System.out.println(DateTimeFormatter.ofPattern(\"yyyy-MM-DD HH:mm:ss\").format(minusDays));\n    }\n}<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"1024\" height=\"537\" src=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-14-1024x537.png\" alt=\"\" class=\"wp-image-890\" srcset=\"https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-14-1024x537.png 1024w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-14-300x157.png 300w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-14-768x403.png 768w, https:\/\/axinyi.xuenixiang.com\/wp-content\/uploads\/2022\/04\/\u56fe\u7247-14.png 1035w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<h3>7.5.5 \u5176\u5b83\u7684\u65e5\u671f\u65b9\u6cd5<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import org.junit.Test;\n\nimport java.time.*;\nimport java.time.temporal.TemporalAdjusters;\nimport java.util.Set;\n\n\npublic class DemoTest {\n\n    @Test\n    public void test1(){\n        \/\/\u83b7\u53d6\u65e5\u671f\n        LocalDateTime dateTime = LocalDateTime.now();\n        System.out.println(dateTime.getYear());\n        System.out.println(dateTime.getMonthValue());\n        System.out.println(dateTime.getHour());\n        System.out.println(dateTime.getDayOfWeek());\n        System.out.println(dateTime.getDayOfYear());\n    }\n\n    @Test\n    public void test2(){\n        \/\/\u65f6\u95f4\u6233\n        System.out.println(\"\u957f\u6574\u578b\u65f6\u95f4\u6233\uff1a\"+System.currentTimeMillis());\n    }\n\n    @Test\n    public void test3(){\n        \/\/\u65f6\u95f4\u6233\n        Instant instant = Instant.now();\n        \/\/\u6211\u4eec\u7684\u65f6\u533a\u548c\u6807\u51c6\u9ed8\u8ba4\u7684\u65f6\u533a\u76f8\u5dee8\u5c0f\u65f6\n        System.out.println(\"\u9ed8\u8ba4\u7684\u65f6\u533a\"+instant);\n        \/\/\u5fc5\u987b\u6dfb\u52a0\u4e0a\u76f8\u5dee\u76848\u5c0f\u65f6\n        OffsetDateTime offsetDateTime = instant.atOffset(ZoneOffset.ofHours(8));\n        System.out.println(\"\u6211\u4eec\u7684\u65f6\u533a\u65f6\u95f4\"+offsetDateTime);\n        \/\/\u83b7\u53d6\u65f6\u95f4\u6233\n        System.out.println(\"\u83b7\u53d6\u65f6\u95f4\u6233\"+offsetDateTime.toEpochSecond());\n    }\n\n    @Test\n    public void test4(){\n        LocalDateTime dateTime1 = LocalDateTime.of(2021, 12, 25, 14, 25);\n        LocalDateTime dateTime2 = LocalDateTime.of(2021, 12, 28, 14, 25);\n\n        \/\/\u5dee\n        Duration duration = Duration.between(dateTime1, dateTime2);\n        System.out.println(\"\u5929\u6570\uff1a\"+duration.toDays());\n        System.out.println(\"\u79d2\u6570\uff1a\"+duration.getSeconds());\n    }\n\n    @Test\n    public void test5(){\n        \/\/\u8ba1\u7b97\u65e5\u671f\u5dee\n        LocalDate date1 = LocalDate.of(2022, 02, 11);\n        LocalDate date2 = LocalDate.of(2022, 03, 11);\n\n        \/\/\u5dee\n        Period between = Period.between(date1, date2);\n        System.out.println(\"\u5929\u6570\uff1a\"+between.getDays());\n        System.out.println(\"\u6708\u6570\uff1a\"+between.getMonths());\n    }\n\n    @Test\n    public void test6(){\n        \/\/\u65f6\u95f4\u6821\u6b63\u5668\n        LocalDateTime dateTime = LocalDateTime.now();\n        \/\/\u83b7\u53d6\u4e0b\u4e00\u5929\n        LocalDateTime with = dateTime.with(TemporalAdjusters.lastDayOfMonth());\n        System.out.println(with);\n    }\n\n    @Test\n    public void test7(){\n        \/\/\u67e5\u770b\u65f6\u533a\n        Set&lt;String> set = ZoneId.getAvailableZoneIds();\n        set.forEach(System.out::println);\n    }\n\n    @Test\n    public void test8(){\n        \/\/\u6307\u5b9a\u65f6\u533a\n        LocalDateTime now = LocalDateTime.now();\n        ZonedDateTime az = now.atZone(ZoneId.of(\"Asia\/Shanghai\"));\n        System.out.println(az);\n        \/\/\u53ef\u4ee5\u770b\u5230\u67098\u5c0f\u65f6\u7684\u5dee\u503c\uff1a2022-03-22T18:32:05.812+08:00&#91;Asia\/Shanghai]\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.6 \u6570\u5b57\u7c7b<\/h2>\n\n\n\n<h3>7.6.1 \u8d27\u5e01\u7c7b\u578bDecimalFormat<\/h3>\n\n\n\n<ul><li>\u6848\u4f8b\uff1a\u5343\u8fdb\u4f4d\u7b26<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>import java.text.DecimalFormat;\n\npublic class Demo {\n    public static void main(String&#91;] args) {\n        \/\/\u8d27\u5e01\u683c\u5f0f\n        DecimalFormat decimalFormat = new DecimalFormat(\"###,###.##\");\n        String format = decimalFormat.format(123456.123456);\n        System.out.println(format);\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u6848\u4f8b\uff1a\u89c4\u5b9a\u5c0f\u6570\u7684\u4f4d\u6570<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>import java.text.DecimalFormat;\n\npublic class Demo {\n    public static void main(String&#91;] args) {\n        \/\/\u8d27\u5e01\u683c\u5f0f\n        DecimalFormat decimalFormat = new DecimalFormat(\"###,###.0000\");\n        String format = decimalFormat.format(123456.127);\n        System.out.println(format);\n    }\n}<\/code><\/pre>\n\n\n\n<h3>7.6.2 \u4f7f\u7528\u8d22\u52a1\u6570\u636eBigDecimal<\/h3>\n\n\n\n<ul><li>\u53ef\u4ee5\u4f7f\u7528\u8d22\u52a1\u6570\u636e\u7684\u4e13\u7528\u65b9\u6cd5<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>import java.math.BigDecimal;\n\npublic class Demo {\n    public static void main(String&#91;] args) {\n        \/\/\u8d22\u52a1\u6570\u636e\n        BigDecimal v1 = new BigDecimal(20);\n        BigDecimal v2 = new BigDecimal(30);\n        \n        \/\/\u76f8\u52a0\n        BigDecimal add = v1.add(v2);\n        System.out.println(add);\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.7 Random\u968f\u673a\u6570<\/h2>\n\n\n\n<h3>7.7.1 \u968f\u673a\u6570\u7684\u8303\u56f40-1<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    public static void main(String&#91;] args) {\n        double random = Math.random();\n        System.out.println(random);\n    }\n}<\/code><\/pre>\n\n\n\n<h3>7.7.2 \u5de5\u5177\u5305\u4e0b\u7684\u968f\u673a\u6570<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>import java.util.Random;\n\npublic class Demo {\n    public static void main(String&#91;] args) {\n        Random random = new Random();\n        \/\/\u53ef\u4ee5\u6307\u5b9a\u968f\u673a\u6570\u7684\u8303\u56f4\n        for (int i = 0; i &lt; 10; i++) {\n            int n = random.nextInt(10);\n            System.out.println(n);\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.8 Enum\u679a\u4e3e\u7c7b\u578b<\/h2>\n\n\n\n<ul><li>\u679a\u4e3e\u5c31\u662f\u4e3a\u4e86\u5b9a\u4e49\u6807\u51c6\uff0c\u679a\u4e3e\u4e2d\u7684\u53c2\u6570\u90fd\u662f\u5e38\u91cf\u3002<\/li><\/ul>\n\n\n\n<h3>7.8.1 \u6848\u4f8b<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    public static void main(String&#91;] args) {\n        int i = 10;\n        if (i>=10){\n            System.out.println(Msg.SUCCESS);\n        }else{\n            System.out.println(Msg.FILAURE);\n        }\n    }\n}\n\n\/\/\u521b\u5efa\u679a\u4e3e\u7c7b\nenum Msg{\n    SUCCESS,FILAURE;\n}<\/code><\/pre>\n\n\n\n<h3>7.8.2 \u679a\u4e3e\u7684\u771f\u5b9e\u5e94\u7528\u573a\u666f<\/h3>\n\n\n\n<ul><li>\u521b\u5efa\u679a\u4e3e\u7c7b<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/\u679a\u4e3e\u7c7b\npublic enum Msg {\n    DEL(\"\u5220\u9664\",1),SHOW(\"\u663e\u793a\",0);\n    private String message;\n    private Integer flag;\n\n    \/\/\u542b\u53c2\u6570\u7684\u6784\u9020\u65b9\u6cd5\n    private Msg(String message,int flag){\n        this.message = message;\n        this.flag = flag;\n    }\n\n    public String getMessage() {\n        return message;\n    }\n\n    public Integer getFlag() {\n        return flag;\n    }\n}<\/code><\/pre>\n\n\n\n<ul><li>\u4f7f\u7528<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Demo {\n    public static void main(String&#91;] args) {\n        \/\/\u83b7\u53d6\u6807\u8bc6\u53ca\u5bf9\u5e94\u7684\u6570\u5b57\n        String message = Msg.DEL.getMessage();\n        Integer flag = Msg.DEL.getFlag();\n        \/\/\u663e\u793a\n        System.out.println(message);\n        System.out.println(flag);\n    }\n}<\/code><\/pre>\n\n\n\n<h2>7.9 \u5b9e\u4f53\u7c7b\uff1aJavaBean<\/h2>\n\n\n\n<ul><li>\u6ce8\u610f\uff1a\u5b9e\u4f53\u7c7b\u7684\u5c5e\u6027\u5fc5\u987b\u662f\u5305\u88c5\u7c7b\u578b\uff0c\u56e0\u4e3a\uff0c\u6211\u4eec\u53ea\u9700\u8981\u5224\u65adnull\u6216\u8005\u975enull\u5373\u53ef<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Person {\n    private String username;\n    private String sex;\n    private Integer age;\n\n    public String getUsername() {\n        return username;\n    }\n\n    public void setUsername(String username) {\n        this.username = username;\n    }\n\n    public String getSex() {\n        return sex;\n    }\n\n    public void setSex(String sex) {\n        this.sex = sex;\n    }\n\n    public Integer getAge() {\n        return age;\n    }\n\n    public void setAge(Integer age) {\n        this.age = age;\n    }\n}<\/code><\/pre>\n\n\n\n<p><div class=\"has-toc have-toc\"><\/div><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u7b2c\u4e03\u7ae0 \u5e38\u7528\u7c7b 7.1 String 7.1.1 String\u7c7b\u662f\u4e0d\u53ef\u53d8\u7c7b \u5c31\u662fstring\u5bf9\u8c61\u521b\u5efa\u540e\u4e0d\u53ef\u4ee5\u4fee\u6539 \u6848\u4f8b\uff1a \u4ece\u4e0a\u9762\u56fe &#8230;<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[10],"tags":[],"_links":{"self":[{"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/posts\/875"}],"collection":[{"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/comments?post=875"}],"version-history":[{"count":2,"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/posts\/875\/revisions"}],"predecessor-version":[{"id":893,"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/posts\/875\/revisions\/893"}],"wp:attachment":[{"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/media?parent=875"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/categories?post=875"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/axinyi.xuenixiang.com\/index.php\/wp-json\/wp\/v2\/tags?post=875"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}