\u4f7f\u7528Java 2 SDK\u57fa\u790e\u985e\u5eab\u7522\u751f\u96a8\u6a5f\u6578\u7684\u65b9\u6cd5\u5f88\u591a\u3002\u4f46\u662f\u5982\u679c\u4f60\u8ddf\u4e0d\u4e0a\u9019\u4e9b\u985e\u5eab\u7684\u66f4\u65b0\u8173\u6b65\uff0c\u4f60\u6709\u53ef\u80fd\u6b63\u5728\u4f7f\u7528\u7684\u662f\u4e00\u7a2e\u4f4e\u6548\u7684\u96a8\u6a5f\u6578\u751f\u6210\u6a5f\u5236\uff0c\u66f4\u7cdf\u7cd5\u7684\u662f\uff1a\u4f60\u6709\u53ef\u80fd\u5f97\u5230\u7684\u4e0d\u662f\u5747\u52fb\u5206\u5e03\u7684\u96a8\u6a5f\u6578\u3002\u672c\u6587\u5c07\u5411\u4f60\u5c55\u793a\u4e00\u7a2e\u8f03\u70ba\u53ef\u9760\u7684\u96a8\u6a5f\u6578\u751f\u6210\u65b9\u6cd5\uff0c\u540c\u6642\u8207\u5176\u4ed6\u65b9\u6cd5\u9032\u884c\u6bd4\u8f03\u3002
\n\u81ea\u5f9eJDK\u6700\u521d\u7248\u672c\u767c\u5e03\u8d77\uff0c\u6211\u5011\u5c31\u53ef\u4ee5\u4f7f\u7528java.util.Random\u985e\u7522\u751f\u96a8\u6a5f\u6578\u4e86\u3002\u5728JDK1.2\u4e2d\uff0cRandom\u985e\u6709\u4e86\u4e00\u500b\u540d\u70banextInt()\u7684\u65b9\u6cd5\uff1apublic int nextInt(int n)\u7d66\u5b9a\u4e00\u500b\u53c3\u6578n\uff0cnextInt(n)\u5c07\u8fd4\u56de\u4e00\u500b\u5927\u65bc\u7b49\u65bc0\u5c0f\u65bcn\u7684\u96a8\u6a5f\u6578\uff0c\u5373\uff1a0 <= nextInt(n) < n\u3002\u4f60\u6240\u8981\u505a\u7684\u5c31\u662f\u5148\u8072\u660e\u4e00\u500bRandom\u7684\u5c0d\u8c61\uff0c\u5728\u8abf\u7528\u5176nextInt(n)\u51fd\u6578\u4ee5\u8fd4\u56de\u96a8\u6a5f\u503c\u3002\u9019\u88cf\u6709\u500b\u793a\u4f8b\uff0c\u4e0b\u9762\u7684\u4ee3\u78bc\u6bb5\u5c07\u751f\u6210\u5f88\u591a\u96a8\u6a5f\u6578\u4e26\u8f38\u51fa\u5b83\u5011\u7684\u5e73\u5747\u503c\uff1a<\/p>\n
\u4ee5\u4e0b\u662f\u5f15\u7528\u7247\u6bb5\uff1a
\n\u3000\u3000int count = 1000000;
\n\u3000\u3000int range = Integer.MAX_VALUE \/ 3 * 2;
\n\u3000\u3000double sum = 0;
\n\u3000\u3000Random rand = new Random();
\n\u3000\u3000for (int i=0; i<count; i++) {
\n\u3000\u3000sum += rand.nextInt(range);
\n\u3000\u3000}
\n\u3000\u3000System.out.println(sum\/count);<\/p>\n
\u57f7\u884c\u4e861000000\u6b21\u5faa\u74b0\u4e4b\u5f8c\uff0c\u5f97\u5230\u7684\u5e73\u5747\u503c\u57fa\u672c\u4e0a\u5c31\u8655\u65bc\u96a8\u6a5f\u6578\u7bc4\u570d\u7684\u4e2d\u9ede\uff08midpoint\uff09\u3002<\/p>\n
\u3000\u3000\u5230\u76ee\u524d\u70ba\u6b62\uff0c\u4e8b\u60c5\u9084\u4e26\u4e0d\u5fa9\u96dc\uff0c\u4f46\u662f\u6211\u5011\u6703\u554f\u70ba\u4ec0\u9ebd\u8981\u4f7f\u7528nextInt(n)\uff1f\u8003\u616e\u4e00\u4e0b\u7684\u96a8\u6a5f\u6578\u751f\u6210\u65b9\u6cd5\uff1a
\n\u3000\u3000(1)\u4f7f\u7528\u8001\u7684\u65b9\u6cd5nextInt()\uff0c\u6c92\u6709\u5236\u5b9a\u6578\u503c\u7bc4\u570d
\n\u3000\u3000(2)\u7528Math.abs()\u975c\u614b\u51fd\u6578\u5f97\u5230(1)\u4e2d\u7522\u751f\u503c\u7684\u7d55\u5c0d\u503c
\n\u3000\u3000(3)\u5c0d(2)\u7684\u7d50\u679c\u9032\u884c\u53d6\u6a21\u904b\u7b97(%)\uff0c\u5f97\u5230\u671f\u671b\u7bc4\u570d\u985e\u7684\u503c<\/p>\n
\u3000\u3000\u6211\u5011\u8aaanextInt(n)\u8981\u6bd4\u4e0a\u8ff0\u65b9\u6cd5\u66f4\u597d\uff0c\u70ba\u4ec0\u9ebd\u5462\uff1f\u53c3\u8003\u4ee5\u4e0b\u7684\u4ee3\u78bc\u6bb5\uff1a<\/p>\n
\u4ee5\u4e0b\u662f\u5f15\u7528\u7247\u6bb5\uff1a
\n\u3000\u3000sum = 0;
\n\u3000\u3000for (int i=0; i<count; i++) {
\n\u3000\u3000sum += Math.abs(rand.nextInt()) % range;
\n\u3000\u3000}
\n\u3000\u3000System.out.println(sum\/count);
\n\u3000\u3000\u4e0d\u96e3\u767c\u73fe\uff0c\u6bcf\u6b21\u5faa\u74b0\u90fd\u591a\u51fa\u4e86\u5e7e\u6b65\u904b\u7b97\u3002\u4e8b\u5be6\u4e0a\uff0c\u9019\u7a2e\u96a8\u6a5f\u6578\u751f\u6210\u7684\u65b9\u6cd5\u5b58\u5728\u8457\u4ee5\u4e0b\u4e09\u500b\u554f\u984c\uff1a<\/p>\n
\u3000\u3000\u9996\u5148\uff0cnextInt()\u8fd4\u56de\u7684\u503c\u662f\u8da8\u65bc\u5747\u52fb\u5206\u5e03\u5728Integer.MIN_VALUE \u548c Integer.MAX_VALUE\u4e4b\u9593\u7684\u3002\u5982\u679c\u4f60\u53d6Integer.MIN_VALUE\u7684\u7d55\u5c0d\u503c\uff0c\u5f97\u5230\u7684\u4ecd\u7136\u4e0d\u662f\u4e00\u500b\u6b63\u6578\u3002\u4e8b\u5be6\u4e0a\uff0cMath.abs(Integer.MIN_VALUE)\u7b49\u65bcInteger.MIN_VALUE\u3002\u56e0\u6b64\uff0c\u5b58\u5728\u8457\u9019\u6a23\u4e00\u7a2e\u60c5\u6cc1\uff08\u96d6\u7136\u5f88\u5c11\u898b\uff09\uff1arand.nextInt()=Integer.MIN_VALUE\uff0c\u7d93\u904e\u53d6\u7d55\u5c0d\u503cMath.abs(rand.nextInt())\u4e4b\u5f8c\uff0c\u5f97\u5230\u662f\u4e00\u500b\u8ca0\u6578\u3002\u9019\u7a2e\u5e7e\u7387\u70ba 1\/(2^31)\uff0c\u5728\u6211\u5011\u7684\u6e2c\u8a66\u4e2d\u4e0d\u592a\u53ef\u80fd\u767c\u751f\u2014\u2014\u5faa\u74b0\u6b21\u6578\u53ea\u67091000000\u6b21\u3002
\n\u3000\u3000\u5176\u6b21\uff0c\u7576\u4f60\u5c0dnextInt()\u53d6\u6a21\u6642\uff0c\u4f60\u4f7f\u7d50\u679c\u7684\u96a8\u6a5f\u6027\u5927\u6253\u6298\u6263\u3002\u96a8\u6a5f\u6578\u4e2d\u8f03\u5c0f\u7684\u503c\u51fa\u73fe\u7684\u5e7e\u7387\u66f4\u5927\u4e00\u4e9b\u3002\u9019\u5c31\u662f\u773e\u6240\u5468\u77e5\u7684\u507d\u96a8\u6a5f\u6578\u751f\u6210\uff0c\u56e0\u6b64\u6211\u5011\u4e0d\u662f\u7528\u53d6\u6a21\u7684\u65b9\u6cd5\u3002
\n\u3000\u3000\u6700\u5f8c\uff0c\u4e5f\u53ef\u80fd\u662f\u6700\u7cdf\u7cd5\u7684\uff1a\u96a8\u6a5f\u6578\u4e0d\u662f\u5747\u52fb\u5206\u5e03\u3002\u5982\u679c\u4f60\u57f7\u884c\u4e86\u4e0a\u8ff0\u7684\u5169\u6bb5\u4ee3\u78bc\uff0c\u7b2c\u4e00\u6bb5\u4ee3\u78bc\u7684\u7d50\u679c\u5c07\u6703\u5927\u65bc715,000,000\uff0c\u8003\u616e\u5230\u6578\u503c\u7bc4\u570d\u7684\u4e2d\u9ede\uff08midpoint)715,827,882\uff0c\u6240\u4ee5\u9019\u662f\u4e00\u500b\u53ef\u4ee5\u63a5\u53d7\u7684\u7d50\u679c\u3002\u7136\u800c\uff0c\u4f60\u6703\u5403\u9a5a\u7684\u767c\u73fe\u7b2c\u4e8c\u6bb5\u4ee3\u78bc\u5f97\u5230\u7684\u5e73\u5747\u503c\u80af\u5b9a\u4e0d\u6703\u8d85\u904e600,000,000\u3002<\/p>\n
\u3000\u3000\u70ba\u4f55\u7b2c\u4e8c\u6bb5\u4ee3\u78bc\u7684\u7d50\u679c\u6703\u5982\u6b64\u7684\u504f\u5dee\uff1f\u7cfe\u5176\u672c\u8cea\uff0c\u554f\u984c\u51fa\u5728\u6578\u503c\u5206\u5e03\u7684\u4e0d\u5747\u52fb\u3002\u7576\u4f60\u9032\u884c\u53d6\u6a21\u904b\u7b97\u6642\uff0c\u4f60\u5c07\u904e\u5927\u7684\u6578\u8f49\u63db\u6210\u4e86\u8f03\u5c0f\u7684\u3002\u9019\u4f7f\u5f97\u8f03\u5c0f\u7684\u6578\u66f4\u5bb9\u6613\u7522\u751f\u3002<\/p>\n
\u3000\u3000\u4f7f\u7528nextInt(range)\u5c07\u6703\u89e3\u6c7a\u4e0a\u8ff0\u7684\u4e09\u500b\u554f\u984c\u3002\u9084\u6709\u4e00\u7a2e\u96a8\u6a5f\u6578\u751f\u6210\u65b9\u6cd5\u2014\u2014\u4f7f\u7528Math.random()\u3002\u9019\u500b\u65b9\u6cd5\u7684\u6548\u679c\u5982\u4f55\uff1f<\/p>\n
\u4ee5\u4e0b\u662f\u5f15\u7528\u7247\u6bb5\uff1a
\n\u3000\u3000sum = 0;
\n\u3000\u3000for (int i=0; i<count; i++) {
\n\u3000\u3000sum += (int)(Math.random() * range);
\n\u3000\u3000}
\n\u3000\u3000System.out.println(sum\/count);
\n\u5f88\u597d\uff0c\u4f7f\u7528random()\u4e0d\u6703\u78b0\u5230nextInt()\u7684\u9ebb\u7169\u3002\u4f60\u4e0d\u6703\u5f97\u5230\u8ca0\u6578\u8fd4\u56de\u503c\uff0c\u6c92\u6709\u4f7f\u7528\u53d6\u6a21\u904b\u7b97\uff0c\u503c\u5206\u5e03\u4e5f\u662f\u5747\u52fb\u7684\u3002\u9084\u6709\u4ec0\u9ebd\u554f\u984c\u55ce\uff1f\u4f60\u6709\u6c92\u6709\u8003\u616e\u5230Math.random()\u4f7f\u7528\u4e86\u6d6e\u9ede\u904b\u7b97\uff0c\u800cnextInt()\u548cnextInt(range)\u53ea\u6709\u6574\u6578\u64cd\u4f5c\uff1fMath.random()\u53ef\u80fd\u6703\u6162\u4e0a\u56db\u500d\u3002\u518d\u52a0\u4e0a\u5f9e\u6d6e\u9ede\u5230\u6574\u6578\u7684\u985e\u578b\u8f49\u63db\uff0c\u6574\u500b\u904b\u7b97\u5c07\u6703\u66f4\u6162\u3002\u597d\u4e86\uff0c\u7d93\u904e\u4e00\u756a\u6bd4\u8f03\uff0c\u6211\u5011\u767c\u73fe\u4f7f\u7528nextInt(range)\u751f\u6210\u96a8\u6a5f\u6578\u66f4\u70ba\u6709\u6548\uff0c\u56e0\u70ba\u5b83\u907f\u514d\u4e86\u5176\u4ed6\u65b9\u6cd5\u7684\u7a2e\u7a2e\u5f0a\u7aef\u3002\u6700\u5f8c\u518d\u7d66\u51fa\u4e00\u6bb5\u4ee3\u78bc\uff0c\u901a\u904e\u6e2c\u8a66\u53ef\u4ee5\u6bd4\u8f03\u672c\u6587\u63d0\u5230\u7684\u5e7e\u7a2e\u96a8\u6a5f\u6578\u751f\u6210\u65b9\u6cd5\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4f7f\u7528Java 2 SDK\u57fa\u790e\u985e\u5eab\u7522\u751f\u96a8\u6a5f\u6578\u7684\u65b9\u6cd5\u5f88\u591a\u3002\u4f46\u662f\u5982\u679c\u4f60\u8ddf\u4e0d\u4e0a\u9019\u4e9b\u985e\u5eab\u7684\u66f4\u65b0\u8173\u6b65\uff0c\u4f60\u6709\u53ef\u80fd\u6b63\u5728\u4f7f\u7528\u7684\u662f\u4e00\u7a2e\u4f4e\u6548\u7684\u96a8\u6a5f\u6578\u751f\u6210\u6a5f\u5236\uff0c\u66f4\u7cdf\u7cd5\u7684\u662f\uff1a\u4f60\u6709\u53ef\u80fd\u5f97\u5230\u7684\u4e0d\u662f\u5747\u52fb\u5206\u5e03\u7684\u96a8\u6a5f\u6578\u3002\u672c\u6587\u5c07\u5411\u4f60\u5c55\u793a\u4e00\u7a2e\u8f03\u70ba\u53ef\u9760\u7684\u96a8\u6a5f\u6578\u751f\u6210\u65b9\u6cd5\uff0c\u540c\u6642\u8207\u5176\u4ed6\u65b9\u6cd5\u9032\u884c\u6bd4\u8f03\u3002 \u81ea\u5f9eJDK\u6700\u521d\u7248\u672c\u767c\u5e03\u8d77\uff0c\u6211\u5011\u5c31\u53ef\u4ee5\u4f7f\u7528java.util.Random\u985e\u7522\u751f\u96a8\u6a5f\u6578\u4e86\u3002\u5728JDK1.2\u4e2d\uff0cRandom\u985e\u6709\u4e86\u4e00\u500b\u540d\u70banextInt()\u7684\u65b9\u6cd5\uff1apublic int nextInt(int n)\u7d66\u5b9a\u4e00\u500b\u53c3\u6578n\uff0cnextInt(n)\u5c07\u8fd4\u56de\u4e00\u500b\u5927\u65bc\u7b49\u65bc0\u5c0f\u65bcn\u7684\u96a8\u6a5f\u6578\uff0c\u5373\uff1a0 <= nextInt(n) < n\u3002\u4f60\u6240\u8981\u505a\u7684\u5c31\u662f\u5148\u8072\u660e\u4e00\u500bRandom\u7684\u5c0d\u8c61\uff0c\u5728\u8abf\u7528\u5176nextInt(n)\u51fd\u6578\u4ee5\u8fd4\u56de\u96a8\u6a5f\u503c\u3002\u9019\u88cf\u6709\u500b\u793a\u4f8b\uff0c\u4e0b\u9762\u7684\u4ee3\u78bc\u6bb5\u5c07\u751f\u6210\u5f88\u591a\u96a8\u6a5f\u6578\u4e26\u8f38\u51fa\u5b83\u5011\u7684\u5e73\u5747\u503c\uff1a \u4ee5\u4e0b\u662f\u5f15\u7528\u7247\u6bb5\uff1a \u3000\u3000int count = 1000000; \u3000\u3000int range = Integer.MAX_VALUE \/ 3 * 2; \u3000\u3000double sum = 0; \u3000\u3000Random rand = new Random(); \u3000\u3000for (int i=0; i<count; i++) { \u3000\u3000sum += rand.nextInt(range); \u3000\u3000} \u3000\u3000System.out.println(sum\/count); \u57f7\u884c\u4e861000000\u6b21\u5faa\u74b0\u4e4b\u5f8c\uff0c\u5f97\u5230\u7684\u5e73\u5747\u503c\u57fa\u672c\u4e0a\u5c31\u8655\u65bc\u96a8\u6a5f\u6578\u7bc4\u570d\u7684\u4e2d\u9ede\uff08midpoint\uff09\u3002 \u3000\u3000\u5230\u76ee\u524d\u70ba\u6b62\uff0c\u4e8b\u60c5\u9084\u4e26\u4e0d\u5fa9\u96dc\uff0c\u4f46\u662f\u6211\u5011\u6703\u554f\u70ba\u4ec0\u9ebd\u8981\u4f7f\u7528nextInt(n)\uff1f\u8003\u616e\u4e00\u4e0b\u7684\u96a8\u6a5f\u6578\u751f\u6210\u65b9\u6cd5\uff1a \u3000\u3000(1)\u4f7f\u7528\u8001\u7684\u65b9\u6cd5nextInt()\uff0c\u6c92\u6709\u5236\u5b9a\u6578\u503c\u7bc4\u570d \u3000\u3000(2)\u7528Math.abs()\u975c\u614b\u51fd\u6578\u5f97\u5230(1)\u4e2d\u7522\u751f\u503c\u7684\u7d55\u5c0d\u503c \u3000\u3000(3)\u5c0d(2)\u7684\u7d50\u679c\u9032\u884c\u53d6\u6a21\u904b\u7b97(%)\uff0c\u5f97\u5230\u671f\u671b\u7bc4\u570d\u985e\u7684\u503c \u3000\u3000\u6211\u5011\u8aaanextInt(n)\u8981\u6bd4\u4e0a\u8ff0\u65b9\u6cd5\u66f4\u597d\uff0c\u70ba\u4ec0\u9ebd\u5462\uff1f\u53c3\u8003\u4ee5\u4e0b\u7684\u4ee3\u78bc\u6bb5\uff1a \u4ee5\u4e0b\u662f\u5f15\u7528\u7247\u6bb5\uff1a \u3000\u3000sum = 0; \u3000\u3000for […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[3173,3164],"class_list":["post-96","post","type-post","status-publish","format-standard","hentry","category-sun","tag-java","tag-sun"],"_links":{"self":[{"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=\/wp\/v2\/posts\/96","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=96"}],"version-history":[{"count":0,"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=\/wp\/v2\/posts\/96\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=96"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=96"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.killtest.com.tw\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=96"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}