{"id":56,"date":"2015-03-30T09:19:35","date_gmt":"2015-03-30T01:19:35","guid":{"rendered":"https:\/\/ai.zhousir.top\/?p=56"},"modified":"2020-01-11T16:09:36","modified_gmt":"2020-01-11T08:09:36","slug":"string%e5%92%8cstringbuffer","status":"publish","type":"post","link":"https:\/\/ai.zhousir.top\/?p=56","title":{"rendered":"String\u548cStringBuffer"},"content":{"rendered":"

String \u7684\u503c\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u6bcf\u6b21\u5bf9String\u7684\u64cd\u4f5c\u90fd\u4f1a\u751f\u6210\u65b0\u7684String\u5bf9\u8c61\uff0c\u4e0d\u4ec5\u6548\u7387\u4f4e\uff0c\u800c\u4e14\u8017\u8d39\u5927\u91cf\u5185\u5b58\u7a7a\u95f4\u3002<\/p>\n

StringBuffer\u7c7b\u548cString\u7c7b\u4e00\u6837\uff0c\u4e5f\u7528\u6765\u8868\u793a\u5b57\u7b26\u4e32\uff0c\u4f46\u662fStringBuffer\u7684\u5185\u90e8\u5b9e\u73b0\u65b9\u5f0f\u548cString\u4e0d\u540c\uff0c\u5728\u8fdb\u884c\u5b57\u7b26\u4e32\u5904\u7406\u65f6\uff0c\u4e0d\u751f\u6210\u65b0\u7684\u5bf9\u8c61\uff0c\u5728\u5185\u5b58\u4f7f\u7528\u4e0a\u8981\u4f18\u4e8eString\u3002<\/p>\n

<\/p>\n

StringBuffer \u9ed8\u8ba4\u5206\u914d16\u5b57\u8282\u957f\u5ea6\u7684\u7f13\u51b2\u533a\uff0c\u5f53\u5b57\u7b26\u4e32\u8d85\u8fc7\u8be5\u5927\u5c0f\u65f6\uff0c\u4f1a\u81ea\u52a8\u589e\u52a0\u7f13\u51b2\u533a\u957f\u5ea6\uff0c\u800c\u4e0d\u662f\u751f\u6210\u65b0\u7684\u5bf9\u8c61\u3002<\/p>\n

StringBuffer\u4e0d\u50cfString\uff0c\u53ea\u80fd\u901a\u8fc7 new \u6765\u521b\u5efa\u5bf9\u8c61\uff0c\u4e0d\u652f\u6301\u7b80\u5199\u65b9\u5f0f\uff0c\u4f8b\u5982\uff1a<\/p>\n

[java]StringBuffer str1 = new StringBuffer(); \/\/ \u5206\u914d16\u4e2a\u5b57\u8282\u957f\u5ea6\u7684\u7f13\u51b2\u533a
\nStringBuffer str2 = new StringBuffer(512); \/\/ \u5206\u914d512\u4e2a\u5b57\u8282\u957f\u5ea6\u7684\u7f13\u51b2\u533a
\n\/\/ \u5728\u7f13\u51b2\u533a\u4e2d\u5b58\u653e\u4e86\u5b57\u7b26\u4e32\uff0c\u5e76\u5728\u540e\u9762\u9884\u7559\u4e8616\u4e2a\u5b57\u8282\u957f\u5ea6\u7684\u7a7a\u7f13\u51b2\u533a
\nStringBuffer str3 = new StringBuffer("www.scxh.com");[\/java]<\/p>\n

StringBuffer\u7c7b\u7684\u4e3b\u8981\u65b9\u6cd5<\/h3>\n

StringBuffer\u7c7b\u4e2d\u7684\u65b9\u6cd5\u4e3b\u8981\u504f\u91cd\u4e8e\u5bf9\u4e8e\u5b57\u7b26\u4e32\u7684\u64cd\u4f5c\uff0c\u4f8b\u5982\u8ffd\u52a0\u3001\u63d2\u5165\u548c\u5220\u9664\u7b49\uff0c\u8fd9\u4e2a\u4e5f\u662fStringBuffer\u7c7b\u548cString\u7c7b\u7684\u4e3b\u8981\u533a\u522b\u3002\u5b9e\u9645\u5f00\u53d1\u4e2d\uff0c\u5982\u679c\u9700\u8981\u5bf9\u4e00\u4e2a\u5b57\u7b26\u4e32\u8fdb\u884c\u9891\u7e41\u7684\u4fee\u6539\uff0c\u5efa\u8bae\u4f7f\u7528 StringBuffer\u3002
\n1) append() \u65b9\u6cd5<\/strong><\/p>\n

append() \u65b9\u6cd5\u7528\u4e8e\u5411\u5f53\u524d\u5b57\u7b26\u4e32\u7684\u672b\u5c3e\u8ffd\u52a0\u5185\u5bb9\uff0c\u7c7b\u4f3c\u4e8e\u5b57\u7b26\u4e32\u7684\u8fde\u63a5\u3002\u8c03\u7528\u8be5\u65b9\u6cd5\u4ee5\u540e\uff0cStringBuffer\u5bf9\u8c61\u7684\u5185\u5bb9\u4e5f\u53d1\u751f\u6539\u53d8\uff0c\u4f8b\u5982\uff1a<\/p>\n

[java]StringBuffer str = new StringBuffer(\u201cbiancheng100\u201d);
\nstr.append(true);[\/java]<\/p>\n

\u5219\u5bf9\u8c61str\u7684\u503c\u5c06\u53d8\u6210\u201dbiancheng100true\u201d\u3002\u6ce8\u610f\u662fstr\u6307\u5411\u7684\u5185\u5bb9\u53d8\u4e86\uff0c\u4e0d\u662fstr\u7684\u6307\u5411\u53d8\u4e86\u3002<\/p>\n

\u5b57\u7b26\u4e32\u7684\u201d+\u201c\u64cd\u4f5c\u5b9e\u9645\u4e0a\u4e5f\u662f\u5148\u521b\u5efa\u4e00\u4e2aStringBuffer\u5bf9\u8c61\uff0c\u7136\u540e\u8c03\u7528append()\u65b9\u6cd5\u5c06\u5b57\u7b26\u4e32\u7247\u6bb5\u62fc\u63a5\u8d77\u6765\uff0c\u6700\u540e\u8c03\u7528toString()\u65b9\u6cd5\u8f6c\u6362\u4e3a\u5b57\u7b26\u4e32\u3002
\n\u8fd9\u6837\u770b\u6765\uff0cString\u7684\u8fde\u63a5\u64cd\u4f5c\u5c31\u6bd4StringBuffer\u591a\u51fa\u4e86\u4e00\u4e9b\u9644\u52a0\u64cd\u4f5c\uff0c\u6548\u7387\u4e0a\u5fc5\u7136\u4f1a\u6253\u6298\u6263\u3002
\n\u4f46\u662f\uff0c\u5bf9\u4e8e\u957f\u5ea6\u8f83\u5c0f\u7684\u5b57\u7b26\u4e32\uff0c\u201d+\u201c\u64cd\u4f5c\u66f4\u52a0\u76f4\u89c2\uff0c\u66f4\u5177\u53ef\u8bfb\u6027\uff0c\u6709\u4e9b\u65f6\u5019\u53ef\u4ee5\u7a0d\u5fae\u727a\u7272\u4e00\u4e0b\u6548\u7387\u3002<\/p>\n

2) deleteCharAt()<\/strong>
\ndeleteCharAt() \u65b9\u6cd5\u7528\u6765\u5220\u9664\u6307\u5b9a\u4f4d\u7f6e\u7684\u5b57\u7b26\uff0c\u5e76\u5c06\u5269\u4f59\u7684\u5b57\u7b26\u5f62\u6210\u65b0\u7684\u5b57\u7b26\u4e32\u3002\u4f8b\u5982\uff1a<\/p>\n

[java]StringBuffer str = new StringBuffer("abcdef");
\nstr. deleteCharAt(3);[\/java]<\/p>\n

\u8be5\u4ee3\u7801\u5c06\u4f1a\u5220\u9664\u7d22\u5f15\u503c\u4e3a3\u7684\u5b57\u7b26\uff0c\u5373\u201dd\u201c\u5b57\u7b26\u3002<\/p>\n

\u4f60\u4e5f\u53ef\u4ee5\u901a\u8fc7delete()\u65b9\u6cd5\u4e00\u6b21\u6027\u5220\u9664\u591a\u4e2a\u5b57\u7b26\uff0c\u4f8b\u5982\uff1a<\/p>\n

[java]StringBuffer str = new StringBuffer("abcdef");
\nstr.delete(1, 4);[\/java]<\/p>\n

\u8be5\u4ee3\u7801\u4f1a\u5220\u9664\u7d22\u5f15\u503c\u4e3a1~4\u4e4b\u95f4\u7684\u5b57\u7b26\uff0c\u5305\u62ec\u7d22\u5f15\u503c1\uff0c\u4f46\u4e0d\u5305\u62ec4\u3002<\/p>\n

3) insert() \u65b9\u6cd5<\/strong>
\ninsert() \u7528\u6765\u5728\u6307\u5b9a\u4f4d\u7f6e\u63d2\u5165\u5b57\u7b26\u4e32\uff0c\u53ef\u4ee5\u8ba4\u4e3a\u662fappend()\u7684\u5347\u7ea7\u7248\u3002\u4f8b\u5982\uff1a<\/p>\n

[java]StringBuffer str = new StringBuffer("abcdef");
\nstr.insert(3, "xyz");[\/java]<\/p>\n

\u6700\u540estr\u6240\u6307\u5411\u7684\u5b57\u7b26\u4e32\u4e3a abcdxyzef\u3002<\/p>\n

4) setCharAt() \u65b9\u6cd5<\/strong>
\nsetCharAt() \u65b9\u6cd5\u7528\u6765\u4fee\u6539\u6307\u5b9a\u4f4d\u7f6e\u7684\u5b57\u7b26\u3002\u4f8b\u5982\uff1a<\/p>\n

[java]StringBuffer str = new StringBuffer("abcdef");
\nstr.setCharAt(3, ‘z’);[\/java]<\/p>\n

\u8be5\u4ee3\u7801\u5c06\u628a\u7d22\u5f15\u503c\u4e3a3\u7684\u5b57\u7b26\u4fee\u6539\u4e3a z\uff0c\u6700\u540estr\u6240\u6307\u5411\u7684\u5b57\u7b26\u4e32\u4e3a abczef\u3002<\/p>\n

\u4ee5\u4e0a\u4ec5\u4ec5\u662f\u90e8\u5206\u5e38\u7528\u65b9\u6cd5\u7684\u7b80\u5355\u8bf4\u660e\uff0c\u66f4\u591a\u65b9\u6cd5\u548c\u89e3\u91ca\u8bf7\u67e5\u9605API\u6587\u6863\u3002<\/p>\n

String\u548cStringBuffer\u7684\u6548\u7387\u5bf9\u6bd4<\/h3>\n

\u4e3a\u4e86\u66f4\u52a0\u660e\u663e\u5730\u770b\u51fa\u5b83\u4eec\u7684\u6267\u884c\u6548\u7387\uff0c\u4e0b\u9762\u7684\u4ee3\u7801\uff0c\u5c0626\u4e2a\u82f1\u6587\u5b57\u6bcd\u52a0\u4e8610000\u6b21\u3002<\/p>\n

[java]public class Demo {
\n\u00a0\u00a0\u00a0 public static void main(String[] args){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 String fragment = "abcdefghijklmnopqrstuvwxyz";
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 int times = 10000;
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/ \u901a\u8fc7String\u5bf9\u8c61
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 long timeStart1 = System.currentTimeMillis();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 String str1 = "";
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 for (int i=0; i<times; i++) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 str1 += fragment;
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 long timeEnd1 = System.currentTimeMillis();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System.out.println("String: " + (timeEnd1 – timeStart1) + "ms");
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \/\/ \u901a\u8fc7StringBuffer
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 long timeStart2 = System.currentTimeMillis();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 StringBuffer str2 = new StringBuffer();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 for (int i=0; i<times; i++) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 str2.append(fragment);
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 long timeEnd2 = System.currentTimeMillis();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System.out.println("StringBuffer: " + (timeEnd2 – timeStart2) + "ms");
\n\u00a0\u00a0\u00a0 }
\n}
\n\u8fd0\u884c\u7ed3\u679c\uff1a
\nString: 5287ms
\nStringBuffer: 3ms
\n[\/java]<\/p>\n

\u7ed3\u8bba\u5f88\u660e\u663e\uff0cStringBuffer\u7684\u6267\u884c\u6548\u7387\u6bd4String\u5feb\u4e0a\u5343\u500d\uff0c\u8fd9\u4e2a\u5dee\u5f02\u968f\u7740\u53e0\u52a0\u6b21\u6570\u7684\u589e\u52a0\u8d8a\u6765\u8d8a\u660e\u663e\uff0c\u5f53\u53e0\u52a0\u6b21\u6570\u8fbe\u523030000\u6b21\u7684\u65f6\u5019\uff0c\u8fd0\u884c\u7ed3\u679c\u4e3a\uff1a
\nString: 35923ms
\nStringBuffer: 8ms<\/p>\n

\u6240\u4ee5\uff0c\u5f3a\u70c8\u5efa\u8bae\u5728\u6d89\u53ca\u5927\u91cf\u5b57\u7b26\u4e32\u64cd\u4f5c\u65f6\u4f7f\u7528StringBuffer\u3002<\/p>\n

StringBuilder\u7c7b<\/h3>\n

StringBuilder\u7c7b\u548cStringBuffer\u7c7b\u529f\u80fd\u57fa\u672c\u76f8\u4f3c\uff0c\u65b9\u6cd5\u4e5f\u5dee\u4e0d\u591a\uff0c\u4e3b\u8981\u533a\u522b\u5728\u4e8eStringBuffer\u7c7b\u7684\u65b9\u6cd5\u662f\u591a\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u800cStringBuilder\u4e0d\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u76f8\u6bd4\u800c\u8a00\uff0cStringBuilder\u7c7b\u4f1a\u7565\u5fae\u5feb\u4e00\u70b9\u3002<\/p>\n

StringBuffer\u3001StringBuilder\u3001String\u4e2d\u90fd\u5b9e\u73b0\u4e86CharSequence\u63a5\u53e3\u3002<\/p>\n

CharSequence\u662f\u4e00\u4e2a\u5b9a\u4e49\u5b57\u7b26\u4e32\u64cd\u4f5c\u7684\u63a5\u53e3\uff0c\u5b83\u53ea\u5305\u62eclength()\u3001charAt(int index)\u3001subSequence(int start, int end) \u8fd9\u51e0\u4e2aAPI\u3002<\/p>\n

StringBuffer\u3001StringBuilder\u3001String\u5bf9CharSequence\u63a5\u53e3\u7684\u5b9e\u73b0\u8fc7\u7a0b\u4e0d\u4e00\u6837\uff0c\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n

 <\/p>\n

\u53ef\u89c1\uff0cString\u76f4\u63a5\u5b9e\u73b0\u4e86CharSequence\u63a5\u53e3\uff1bStringBuilder \u548c StringBuffer\u90fd\u662f\u53ef\u53d8\u7684\u5b57\u7b26\u5e8f\u5217\uff0c\u5b83\u4eec\u90fd\u7ee7\u627f\u4e8eAbstractStringBuilder\uff0c\u5b9e\u73b0\u4e86CharSequence\u63a5\u53e3\u3002<\/p>\n

\u603b\u7ed3
\n\u7ebf\u7a0b\u5b89\u5168\uff1a
\nStringBuffer\uff1a\u7ebf\u7a0b\u5b89\u5168
\nStringBuilder\uff1a\u7ebf\u7a0b\u4e0d\u5b89\u5168<\/p>\n

\u901f\u5ea6\uff1a
\n\u4e00\u822c\u60c5\u51b5\u4e0b\uff0c\u901f\u5ea6\u4ece\u5feb\u5230\u6162\u4e3a StringBuilder > StringBuffer > String\uff0c\u5f53\u7136\u8fd9\u662f\u76f8\u5bf9\u7684\uff0c\u4e0d\u662f\u7edd\u5bf9\u7684\u3002<\/p>\n

\u4f7f\u7528\u73af\u5883\uff1a
\n\u64cd\u4f5c\u5c11\u91cf\u7684\u6570\u636e\u4f7f\u7528 String\uff1b
\n\u5355\u7ebf\u7a0b\u64cd\u4f5c\u5927\u91cf\u6570\u636e\u4f7f\u7528 StringBuilder\uff1b
\n\u591a\u7ebf\u7a0b\u64cd\u4f5c\u5927\u91cf\u6570\u636e\u4f7f\u7528 StringBuffer\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

String \u7684\u503c\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u6bcf\u6b21\u5bf9String\u7684\u64cd\u4f5c\u90fd\u4f1a\u751f\u6210\u65b0\u7684String\u5bf9\u8c61\uff0c\u4e0d\u4ec5\u6548\u7387\u4f4e\uff0c\u800c\u4e14\u8017\u8d39\u5927\u91cf\u5185 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[15],"tags":[29],"_links":{"self":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/56"}],"collection":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=56"}],"version-history":[{"count":11,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/56\/revisions"}],"predecessor-version":[{"id":2367,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/56\/revisions\/2367"}],"wp:attachment":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=56"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=56"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=56"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}