{"id":1077,"date":"2022-10-22T21:30:03","date_gmt":"2022-10-22T13:30:03","guid":{"rendered":"https:\/\/qaqaq.top\/?p=1077"},"modified":"2022-11-27T12:39:50","modified_gmt":"2022-11-27T04:39:50","slug":"%e5%85%b3%e4%ba%8estring%e5%ba%95%e5%b1%82%e4%bd%bf%e7%94%a8%e7%9a%84%e6%98%afchar%e6%95%b0%e7%bb%84%e8%bf%98%e6%98%afbyte%e6%95%b0%e7%bb%84%e4%bb%a5%e5%8f%8a%e4%b8%80%e7%82%b9string%e9%9d%a2%e8%af%95","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=1077","title":{"rendered":"\u5173\u4e8eString\u5e95\u5c42\u4f7f\u7528\u7684\u662fchar\u6570\u7ec4\u8fd8\u662fbyte\u6570\u7ec4\u4ee5\u53ca\u4e00\u70b9String\u9762\u8bd5\u95ee\u9898"},"content":{"rendered":"\n

\u5148\u4e0a\u7ed3\u8bba\uff1ajdk1.8\u53ca\u4ee5\u524dString\u4f7f\u7528\u7684\u662fchar\u6570\u7ec4\uff0cjdk1.9\u53ca\u4ee5\u540e\u4f7f\u7528\u7684\u662fbyte\u6570\u7ec4\u3002<\/p>\n\n\n\n

\u56e0\u4e3a\u5f00\u53d1\u4eba\u5458\u53d1\u73b0\u4eba\u4eec\u4f7f\u7528\u7684\u5b57\u7b26\u4e32\u503c\u662f\u62c9\u4e01\u5b57\u7b26\u5c45\u591a\u800c\u4e4b\u524d\u4f7f\u7528\u7684char\u6570\u7ec4\u6bcf\u4e00\u4e2achar\u5360\u7528\u4e24\u4e2a\u5b57\u8282\u800c\u62c9\u4e01\u5b57\u7b26\u53ea\u9700\u8981\u4e00\u4e2a\u5b57\u8282\u5c31\u53ef\u4ee5\u5b58\u50a8\uff0c\u5269\u4e0b\u7684\u4e00\u4e2a\u5b57\u8282\u5c31\u6d6a\u8d39\u4e86\uff0c\u9020\u6210\u5185\u5b58\u7684\u6d6a\u8d39\uff0cgc\u7684\u66f4\u52a0\u9891\u7e41\u3002\u56e0\u6b64\u5728jdk9\u4e2d\u5c06String\u5e95\u5c42\u7684\u5b9e\u73b0\u6539\u4e3a\u4e86byte\u6570\u7ec4\u3002<\/p>\n\n\n\n

\u5728openjdk\u7684\u5f00\u53d1\u65e5\u5fd7\u4e2d\u4e5f\u662f\u6807\u6ce8\u4e86\u8fd9\u4e00\u6539\u52a8\u4ee5\u53ca\u6539\u52a8\u7684\u52a8\u673a\u3002<\/p>\n\n\n\n

\"\"<\/div><\/figure>\n\n\n\n

\u6211\u4eec\u518d\u53bbjdk\u4e2d\u9a8c\u8bc1\u4e00\u4e0b\uff0c\u5148\u662fjdk8<\/p>\n\n\n\n

\"\"<\/div><\/figure>\n\n\n\n

\u786e\u5b9e\u5e95\u5c42\u4f7f\u7528\u7684\u662fchar\u6570\u7ec4\u3002
\u800c\u5230\u4e86jdk9\u65f6\uff0c\u6211\u4eec\u518d\u770b<\/p>\n\n\n\n

\"\"<\/div><\/figure>\n\n\n\n

\u5c31\u53d8\u6210\u4e86byte\u6570\u7ec4\u3002\u90a3\u4e48\u95ee\u9898\u5c31\u6765\u4e86\uff0cString\u662f\u600e\u4e48\u5b9e\u73b0\u5b58\u50a8\u6c49\u5b57\u7684\u5462\uff1f\u6211\u4eec\u5c06jdk9\u7684\u6e90\u7801\u5f80\u4e0b\u7ffb\u770b\u4f1a\u53d1\u73b0\u6709\u4e00\u4e2a\u5c5e\u6027<\/p>\n\n\n\n

\/**\r\n* The identifier of the encoding used to encode the bytes in\r\n* {@code value}. The supported values in this implementation are\r\n*\r\n* LATIN1\r\n* UTF16\r\n*\r\n* @implNote This field is trusted by the VM, and is a subject to\r\n* constant folding if String instance is constant. Overwriting this\r\n* field after construction will cause problems.\r\n*\/\r\nprivate final byte coder;<\/code><\/pre>\n\n\n\n
\u4ec0\u4e48\uff1fcoder\uff1f\u7a0b\u5e8f\u5458\u88ab\u5c01\u88c5\u6210String\u7684\u4e00\u4e2a\u5c5e\u6027\u4e86\uff1f\u6ca1\u6709\u4e70\u5356\u5c31\u6ca1\u6709\u4f24\u5bb3\uff0c\u6bcf\u521b\u5efa\u4e00\u4e2aString\u5c31\u4f1a\u6709\u4e00\u4e2a\u7a0b\u5e8f\u5458\u5931\u53bb\u81ea\u7531\u2026\uff08\u624b\u52a8\u72d7\u5934\uff09<\/p>\n\n\n\n
\u56de\u5f52\u6b63\u9898\uff0c\u5728\u770b\u5230\u4e0a\u9762\u7684\u6ce8\u89e3\u65f6\uff0c\u773c\u524d\u4e00\u4eae \u51fa\u73b0\u4e86Latin\u548cUTF16\u7684\u5b57\u773c\uff0c\u6211\u4eec\u77e5\u9053\u8fd9\u5c31\u662f\u6211\u4eec\u8981\u627e\u7684\u90a3\u4e2a\u201c\u5979\u201d\u3002\u6ce8\u89e3\u4e0a\u8bf4\u660e\u4e86\u8be5\u5c5e\u6027\u5171\u4e24\u4e2a\u5b9e\u73b0Latin1\u548cUTF16\u3002<\/p>\n\n\n\n
\u8fd9\u65f6\u5019\u6211\u4eec\u5c31\u77e5\u9053\u8981\u53bb\u770b\u6784\u9020\u5668\u4e86\uff0c\u800c\u6211\u4eec\u53ea\u9700\u8981\u627e\u5230\u6700\u6839\u6e90\u7684\u6784\u9020\u5668\u5373\u53ef\u3002<\/p>\n\n\n\n
\u770b\u6784\u9020\u5668\u4e4b\u524d\u6211\u4eec\u5148\u770b\u4e00\u4e2a\u5c5e\u6027COMPACT_STRINGS\u3002<\/p>\n\n\n\n
\u7ffb\u8bd1\u8fc7\u6765\u5c31\u662f\u538b\u7f29\u5b57\u7b26\u4e32\uff0c\u9ed8\u8ba4\u9759\u6001\u4ee3\u7801\u5757\u8d4b\u503ctrue\uff1b\u5f88\u660e\u663e\u8fd9\u4e2a\u5c31\u662f\u51b3\u5b9a\u8be5String\u5bf9\u8c61\u662f\u5426\u91c7\u7528\u538b\u7f29\u7b56\u7565\u7684\u5173\u952e\u5c5e\u6027\u3002<\/p>\n\n\n\n
static final boolean COMPACT_STRINGS;\nstatic {\n    COMPACT_STRINGS = true;\n}<\/code><\/pre>\n\n\n\n
\u63a5\u4e0b\u6765\u5c31\u662fString\u7684\u6784\u9020\u5668<\/p>\n\n\n\n
String(char[] value, int off, int len, Void sig) {\n\/\/\u7a7a\u5224\u65ad\n    if (len == 0) {\n        this.value = \"\".value;\n        this.coder = \"\".coder;\n        return;\n    }\n    \/\/\u5982\u679c\u5f00\u542f\u538b\u7f29\u5b57\u7b26\u4e32\u7b56\u7565\u90a3\u4e48\u5c31\u5c1d\u8bd5\u538b\u7f29\n    if (COMPACT_STRINGS) {\n        byte[] val = StringUTF16.compress(value, off, len);\n        if (val != null) {\n            this.value = val;\n            this.coder = LATIN1;\n            return;\n        }\n    }\n    \/\/\u5982\u679c\u6ca1\u6709\u538b\u7f29\u6210\u529f\u5e76\u8fd4\u56de\u5c31\u76f4\u63a5\u8bbe\u7f6e\u4e3aUTF16\uff0c\u6211\u4eec\u70b9\u8fdbUTF16\u6211\u4eec\u4e5f\u53ef\u4ee5\u770b\u5230\u4e0b\u9762\u8fd9\u4e24\u4e2a\u5c5e\u6027\n    this.coder = UTF16;\n    this.value = StringUTF16.toBytes(value, off, len);\n}\n\/\/\u70b9\u8fdb\u4e0a\u9762\u7684UTF16\u627e\u5230\u7684\u4e24\u4e2a\u5c5e\u6027\uff0c\u4e5f\u5c31\u8bc1\u5b9e\u4e86coder\u5c5e\u6027\u4e0a\u9762\u7684\u6ce8\u89e3\uff08\u4e24\u4e2a\u5b9e\u73b0\uff09\r\nstatic final byte LATIN1 = 0;\r\nstatic final byte UTF16 = 1;<\/code><\/pre>\n\n\n\n
\u6700\u540e\u5206\u4eabjava\u5e38\u89c1\u7684\u9762\u8bd5\u95ee\u9898\uff0c\u8003\u8003\u5927\u5bb6<\/p>\n\n\n\n
    String s0=\"java No.1\";\n    String s1=\"java \";\n    String s2=\"No.1\";\n    String s3=\"java \"+\"No.1\";\n    String s4=s1+\"No.1\";\n    String s5=s1+s2;\n    System.out.println(s3==s0);\n    System.out.println(s4==s0);\n    System.out.println(s5==s0);\n    System.out.println(s5==s4);\n    System.out.println(\"-----------------------------\");\n    final String s6=\"I am \";\n    final String s7=\"guYue\";\n    String s8=\"I am guYue\";\n    String s9=s6+s7;\n    System.out.println(s8==s9);<\/code><\/pre>\n\n\n\n
\u7ed3\u679c\u5982\u4e0b<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u5927\u5bb6\u90fd\u7b54\u5bf9\u4e86\u5417\uff1f
\u6211\u603b\u7ed3\u4e86\u4e00\u4e0b\u5171\u6709\u4ee5\u4e0b\u51e0\u79cd\u60c5\u51b5\uff1a
\u2460 \u201c?\u201d+”?”
\u5e95\u5c42\u76f4\u63a5\u4f18\u5316\u4e3a\u201c??\u201d
\u6211\u4eec\u4f7f\u7528jclasslib\u67e5\u770b\u4ee5\u4e0b\u4ee3\u7801\u7684\u5b57\u8282\u7801<\/p>\n\n\n\n
   String s0=\"java No.1\";\n    String s1=\"java \";\n    String s2=\"No.1\";\n    String s3=\"java \"+\"No.1\";<\/code><\/pre>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u770b\u4e0d\u61c2\u5b57\u8282\u7801\u6ca1\u6709\u5173\u7cfb\uff0c\u5f88\u7b80\u5355\u7684 \u6bd4\u5982<\/p>\n\n\n\n
1 . ldc\u5c31\u662f\u4ece\u5e38\u91cf\u6c60\u4e2d\u52a0\u8f7d\u5b57\u7b26\u4e32\u5230\u64cd\u4f5c\u6570\u6808\u4e2d\uff0c<\/p>\n\n\n\n
2 . astore_1\u5c31\u662f\u5c06\u64cd\u4f5c\u6570\u6808\u4e2d\u7684\u5f15\u7528\u7c7b\u578b\u53d8\u91cf\u653e\u5230\u5c40\u90e8\u53d8\u91cf\u8868\u4e2d\u4e0b\u6807\u4e3a1\u7684\u4f4d\u7f6e\u3002<\/p>\n\n\n\n
a\u8868\u793a\u5f15\u7528\u53d8\u91cf\uff0cstore\u8868\u793a\u5b58\u50a8\u5230\u5c40\u90e8\u53d8\u91cf\u8868,_1\u8868\u793a\u5b58\u50a8\u5728\u5c40\u90e8\u53d8\u91cf\u8868\u54ea\u4e2a\u4f4d\u7f6e\u3002<\/p>\n\n\n\n
\u518d\u6bd4\u5982\u6211\u4eec\u73b0\u5728\u8981\u5c06int i=2\uff1b\u653e\u5230\u5c40\u90e8\u53d8\u91cf\u8868\u7684\u4e0b\u6807\u4e3a2\u7684\u4f4d\u7f6e\uff0c\u90a3\u4e48\u5b57\u8282\u7801\u6307\u4ee4\u5c31\u662fistore_2.<\/p>\n\n\n\n
3 . \u5f88\u660e\u663e\u540e\u9762<>\u5305\u8d77\u6765\u7684\u5c31\u662f\u5177\u4f53\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n\n\n\n
\u6240\u4ee5\u6211\u4eec\u73b0\u5728\u5bf9\u5e94\u8d77\u6765\u770b\u53d1\u73b0s0\u548cs3\u7684\u52a0\u8f7d\u8fc7\u7a0b\u5b8c\u5168\u76f8\u540c<\/p>\n\n\n\n
\u2461\u201c?\u201d+si \uff0csi+”?” , si+sj
\u6211\u628a\u8fd9\u4e09\u79cd\u5f52\u4e3a\u4e00\u7c7b\u56e0\u4e3a\u90fd\u6709\u5f15\u7528\u7c7b\u578b\u52a0\u5165\u8fd0\u7b97\u3002<\/p>\n\n\n\n
\u8fd9\u65f6\u5019\u5e95\u5c42\u4f1anew\u4e00\u4e2aStringBuilder\u518d\u8c03\u7528append\u65b9\u6cd5\uff0c\u6700\u540e\u8c03\u7528toString\u65b9\u6cd5\u5b8c\u6210\u62fc\u63a5\u3002\u8fd9\u4e5f\u662f\u4e3a\u4ec0\u4e48\u7981\u6b62\u5728\u5faa\u73af\u4e2d\u8fdb\u884c+\u62fc\u63a5\u5b57\u7b26\u4e32\u7684\u539f\u56e0\uff1a\u4f1anew\u5927\u91cf\u7684StringBuilder\u5bf9\u8c61\uff0c\u9020\u6210\u6548\u7387\uff0c\u8d44\u6e90\u4e0a\u7684\u6d6a\u8d39\u3002<\/p>\n\n\n\n
\u6211\u4eec\u5f00\u5982\u4e0b\u4ee3\u7801\u7684\u5b57\u8282\u7801\u6587\u4ef6<\/p>\n\n\n\n
String s4=s1+\"No.1\";<\/code><\/pre>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
invokexxxxxx\u5c31\u662f\u8c03\u7528\u65b9\u6cd5\u7684\u610f\u601d\uff0c\u5176\u5b9e\u5927\u5bb6\u81ea\u5df1\u731c\u4e5f\u80fd\u731c\u51fa\u6765\u7684\u3002
dup \u5c31\u662f\u5c06\u5b58\u5728\u64cd\u4f5c\u6570\u6808\u4e0a\u7684StringBuilder\u5bf9\u8c61\u7684\u5f15\u7528\u590d\u5236\u4e00\u4efd\u518d\u538b\u5165\u64cd\u4f5c\u6570\u6808<\/p>\n\n\n\n
\u53ea\u8981\u770b<>\u91cc\u9762\u7684\u6570\u636e\u518d\u5bf9\u5e94\u6e90\u4ee3\u7801\u5c31\u53ef\u4ee5\u77e5\u9053\u8fd9\u4e00\u6b65\u5b57\u8282\u7801\u5728\u5e72\u4ec0\u4e48\u4e86\u3002\u6267\u884c\u6d41\u7a0b\u4e0e\u6211\u8ff0\u8bf4\u7684\u8fc7\u7a0b\u5b8c\u5168\u4e00\u81f4\u3002<\/p>\n\n\n\n
\u6211\u4eec\u6700\u540e\u770b\u4e00\u4e0bStringBuilder\u7684toString()\u65b9\u6cd5\u7684\u6e90\u7801\u5c31\u77e5\u9053\u4e86\uff0c\u4ed6\u662fnew \u4e86\u4e00\u4e2aString\u5e76\u8fd4\u56de\u6240\u4ee5\u80af\u5b9a\u4e0d\u662f\u540c\u4e00\u4e2a\u5bf9\u8c61\u3002<\/p>\n\n\n\n
@Override\r\npublic String toString() {\r\n\/\/ Create a copy, don't share the array\r\nreturn new String(value, 0, count);\r\n}<\/code><\/pre>\n\n\n\n
\u2462final s1+final s2
\u8fd9\u662f\u4e24\u4e2afinal\u4fee\u9970\u7684String\u5f15\u7528\u7684\u62fc\u63a5\uff08\u8fd9\u4e2a\u6211\u8bb0\u5fc6\u4e2d\u597d\u591a\u535a\u5ba2\u4e2d\u90fd\u6ca1\u6709\u5217\u4e3e\u8fc7\uff09\uff0c\u6211\u4eec\u770b\u5982\u4e0b\u4ee3\u7801\u7684\u5b57\u8282\u7801<\/p>\n\n\n\n
    final String s6=\"I am \";\n    final String s7=\"guYue\";\n    String s8=\"I am guYue\";\n    String s9=s6+s7;<\/code><\/pre>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u5f88\u660e\u663e\u6700\u540e\u4e24\u4e2a\u64cd\u4f5c\u7684\u5b57\u8282\u7801\u64cd\u4f5c\u8fc7\u7a0b\u90fd\u662f\u76f8\u540c\u7684\uff0c\u5373\u76f4\u63a5\u4ece\u5b57\u7b26\u4e32\u5e38\u91cf\u6c60\u53d6\u3002\u6240\u4ee5\u8fd9\u91cc\u662ftrue\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5148\u4e0a\u7ed3\u8bba\uff1ajdk1.8\u53ca\u4ee5\u524dString\u4f7f\u7528\u7684\u662fchar\u6570\u7ec4\uff0cjdk1.9\u53ca\u4ee5\u540e\u4f7f\u7528\u7684\u662fbyte\u6570\u7ec4\u3002 \u56e0\u4e3a\u5f00 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[33,29],"tags":[46],"class_list":{"0":"post-1077","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"hentry","6":"category-java-","8":"tag-java"},"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1077"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1077"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1077\/revisions"}],"predecessor-version":[{"id":1085,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1077\/revisions\/1085"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1077"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1077"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1077"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}