{"id":4936,"date":"2015-11-05T09:36:06","date_gmt":"2015-11-05T01:36:06","guid":{"rendered":"https:\/\/www.chenqing.work\/?p=4936"},"modified":"2022-10-06T09:37:29","modified_gmt":"2022-10-06T01:37:29","slug":"java-%e7%9a%84%e5%ad%97%e7%ac%a6%e4%b8%b2%e8%bf%9e%e6%8e%a5%e7%ac%a6%ef%bc%88%ef%bc%89","status":"publish","type":"post","link":"https:\/\/www.chenqing.work\/?p=4936","title":{"rendered":"Java \u7684\u5b57\u7b26\u4e32\u8fde\u63a5\u7b26\uff08+\uff09"},"content":{"rendered":"\n<p>\u5728 Java \u4e2d\u5b57\u7b26\u4e32\u662f\u4e00\u4e2a\u5e38\u7528\u7684\u4e1c\u897f\uff0c\u800c\u5176\u4e00\u4e2a\u5e38\u7528\u7684\u64cd\u4f5c\u662f\u5b57\u7b26\u4e32\u7684\u62fc\u63a5\uff0cJava \u5bf9\u6b64\u63d0\u4f9b\u4e86\u4e00\u79cd\u975e\u5e38\u76f4\u89c2\u7684\u64cd\u4f5c\u65b9\u5f0f\u2014\u2014\u5373\u00a0<strong>+<\/strong>\u00a0\u64cd\u4f5c\u7b26\u3002<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: java; title: ; notranslate\" title=\"\">\nString str0 = &quot;a&quot;;\nString str1 = str0 + &quot;b&quot;;\n<\/pre><\/div>\n\n\n<p>\u5982\u4e0a\u7684\u7a0b\u5e8f\u7247\u6bb5\u5c31\u5b9e\u73b0\u4e86\u4e00\u4e2a\u5b57\u7b26\u4e32\u7684\u62fc\u63a5\uff0c\u53ef\u4ee5\u770b\u5230\u6574\u4e2a\u63cf\u8ff0\u975e\u5e38\u7b80\u6d01\uff0c\u4e00\u76ee\u4e86\u7136\u3002\u5b66\u4e60 Java \u7684\u65f6\u5019\uff0c\u8fd9\u662f\u63a5\u89e6\u5230\u7684\u7b2c\u4e00\u79cd\u62fc\u63a5\u5b57\u7b26\u4e32\u7684\u65b9\u5f0f\uff0c\u5148\u5165\u4e3a\u4e3b\u7684\u5370\u8c61\u4f1a\u8ba9\u4f60\u5728\u4ee5\u540e\u9700\u8981\u62fc\u63a5\u5b57\u7b26\u4e32\u65f6\u7b2c\u4e00\u65f6\u95f4\u60f3\u5230\u5b83\uff0c\u4f46\u662f\uff0c\u4f60\u4f1a\u542c\u5230\u5927\u5bb6\u90fd\u8bf4\uff1a\u62fc\u63a5\u5927\u91cf\u7684\u5b57\u7b26\u4e32\u65f6\u4f7f\u7528 StringBuilder \u66f4\u597d\uff0c\u8fd9\u662f\u4e3a\u4ec0\u4e48\u5462\uff1f<\/p>\n\n\n\n<p>\u8ba9\u6211\u4eec\u770b\u770b\u7f16\u8bd1\u5668\u662f\u600e\u4e48\u5904\u7406\u00a0<strong>+<\/strong>\u00a0\u64cd\u4f5c\u7b26\u7684\u3002\u4e0b\u9762\u662f\u4e0a\u4e00\u4e2a\u7a0b\u5e8f\u7247\u6bb5\u7f16\u8bd1\u540e\u7684\u5b57\u8282\u7801\u6307\u4ee4\uff1a<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: java; title: ; notranslate\" title=\"\">\n  public static void main(java.lang.String&#x5B;]);\n    Code:\n       0: ldc           #2                  \/\/ String a\n       2: astore_1\n       3: new           #3                  \/\/ class java\/lang\/StringBuilder\n       6: dup\n       7: invokespecial #4                  \/\/ Method java\/lang\/StringBuilder.&quot;&lt;init&gt;&quot;:()V\n      10: aload_1\n      11: invokevirtual #5                  \/\/ Method java\/lang\/StringBuilder.append:(Ljava\/lang\/String;)Ljava\/lang\/StringBuilder;\n      14: ldc           #6                  \/\/ String b\n      16: invokevirtual #5                  \/\/ Method java\/lang\/StringBuilder.append:(Ljava\/lang\/String;)Ljava\/lang\/StringBuilder;\n      19: invokevirtual #7                  \/\/ Method java\/lang\/StringBuilder.toString:()Ljava\/lang\/String;\n      22: astore_2\n      23: return\n}\n<\/pre><\/div>\n\n\n<p>\u901a\u8fc7\u9605\u8bfb\u8fd9\u6bb5\u5b57\u8282\u7801\uff0c\u53ef\u4ee5\u53d1\u73b0\uff0c\u6211\u4eec\u7684 <strong>+<\/strong> \u62fc\u63a5\u64cd\u4f5c\u5b9e\u9645\u4e0a\u88ab\u7f16\u8bd1\u5668\u7406\u89e3\u6210\u4e86\u8fd9\u4e2a\u6837\u5b50\uff1a<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: java; title: ; notranslate\" title=\"\">\nString str0 = &quot;a&quot;;\nStringBuilder sb = new StringBuilder();\nsb.append(str0).append(&quot;b&quot;);\nString str1 = sb.toString();\n<\/pre><\/div>\n\n\n<p>\u4e2d\u95f4\u591a\u51fa\u6765\u4e86\u4e00\u4e2a StringBuilder \u5bf9\u8c61\uff0c\u8fd9\u662f\u4e00\u4e2a\u4e34\u65f6\u5bf9\u8c61\u3002<\/p>\n\n\n\n<p>\u5047\u8bbe\u6211\u4eec\u73b0\u5728\u6709\u8fd9\u6837\u4e00\u6bb5\u7a0b\u5e8f\u7247\u6bb5\uff1a<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: java; title: ; notranslate\" title=\"\">\nString str0 = &quot;a&quot;;\nfor (int i = 0; i &lt; 10000; i++) {    \n      str0 += &quot;a&quot;;\n}\n<\/pre><\/div>\n\n\n<p>\u518d\u6765\u770b\u770b\u7f16\u8bd1\u540e\u7684\u5b57\u8282\u7801\uff1a<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: java; title: ; notranslate\" title=\"\">\n  public static void main(java.lang.String&#x5B;]);\n    Code:\n       0: ldc           #2                  \/\/ String a\n       2: astore_1\n       3: iconst_0\n       4: istore_2\n       5: iload_2\n       6: sipush        10000\n       9: if_icmpge     38\n      12: new           #3                  \/\/ class java\/lang\/StringBuilder\n      15: dup\n      16: invokespecial #4                  \/\/ Method java\/lang\/StringBuilder.&quot;&lt;init&gt;&quot;:()V\n      19: aload_1\n      20: invokevirtual #5                  \/\/ Method java\/lang\/StringBuilder.append:(Ljava\/lang\/String;)Ljava\/lang\/StringBuilder;\n      23: ldc           #2                  \/\/ String a\n      25: invokevirtual #5                  \/\/ Method java\/lang\/StringBuilder.append:(Ljava\/lang\/String;)Ljava\/lang\/StringBuilder;\n      28: invokevirtual #6                  \/\/ Method java\/lang\/StringBuilder.toString:()Ljava\/lang\/String;\n      31: astore_1\n      32: iinc          2, 1\n      35: goto          5\n      38: return\n}\n<\/pre><\/div>\n\n\n<p>5~35 \u662f\u6211\u4eec\u7684\u5faa\u73af\u4f53\uff0c\u5728\u5faa\u73af\u4f53\u91cc\u9762\uff0c\u6bcf\u6b21\u62fc\u63a5\u90fd\u4f1a\u751f\u6210\u4e00\u4e2a StringBuilder \u7684\u4e34\u65f6\u5bf9\u8c61\uff0c\u90a3\u4e48\u8fd9\u4e2a\u7a0b\u5e8f\u7247\u6bb5\u6267\u884c\u4e0b\u53bb\u5c31\u4f1a\u4ea7\u751f 10000 \u4e2a StringBuilder \u7684\u4e34\u65f6\u5bf9\u8c61\u3002<\/p>\n\n\n\n<p>\u8fd9 10000 \u4e2a\u4e34\u65f6\u5bf9\u8c61\u90fd\u662f\u5fc5\u8981\u7684\u5417\uff1f<\/p>\n\n\n\n<p>\u663e\u7136\u4e0d\u662f\uff0c\u6211\u4eec\u53ef\u4ee5\u5728\u5faa\u73af\u4f53\u5916\u76f4\u63a5\u521b\u5efa\u4e00\u4e2a StringBuilder \u5bf9\u8c61\uff0c\u7136\u540e\u5728\u5faa\u73af\u4f53\u4e2d\u901a\u8fc7 append \u65b9\u6cd5\u62fc\u63a5\u5b57\u7b26\u4e32\uff0c\u8fd9\u6837\u5c31\u7701\u4e0b\u4e86\u521b\u5efa\u5e76\u56de\u6536 10000 \u4e2a\u4e34\u65f6\u5bf9\u8c61\u7684\u6d88\u8017\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\uff0c\u5728\u9700\u8981\u62fc\u63a5\u5927\u91cf\u5b57\u7b26\u4e32\u65f6\uff0c\u8fd8\u662f\u4f7f\u7528 StringBuilder \u5bf9\u8c61\u4e3a\u597d\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728 Java \u4e2d\u5b57\u7b26\u4e32\u662f\u4e00\u4e2a\u5e38\u7528\u7684\u4e1c\u897f\uff0c\u800c\u5176\u4e00\u4e2a\u5e38\u7528\u7684\u64cd\u4f5c\u662f\u5b57\u7b26\u4e32\u7684\u62fc\u63a5\uff0cJava \u5bf9\u6b64\u63d0\u4f9b\u4e86\u4e00\u79cd\u975e [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[110,109],"class_list":["post-4936","post","type-post","status-publish","format-standard","hentry","category-code","tag-110","tag-109"],"_links":{"self":[{"href":"https:\/\/www.chenqing.work\/index.php?rest_route=\/wp\/v2\/posts\/4936","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.chenqing.work\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.chenqing.work\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.chenqing.work\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.chenqing.work\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4936"}],"version-history":[{"count":2,"href":"https:\/\/www.chenqing.work\/index.php?rest_route=\/wp\/v2\/posts\/4936\/revisions"}],"predecessor-version":[{"id":4938,"href":"https:\/\/www.chenqing.work\/index.php?rest_route=\/wp\/v2\/posts\/4936\/revisions\/4938"}],"wp:attachment":[{"href":"https:\/\/www.chenqing.work\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4936"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.chenqing.work\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4936"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.chenqing.work\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4936"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}