{"id":10006318,"date":"2022-08-25T19:52:56","date_gmt":"2022-08-25T11:52:56","guid":{"rendered":"https:\/\/ityet.com\/?p=10006318"},"modified":"2022-08-25T19:52:56","modified_gmt":"2022-08-25T11:52:56","slug":"bigdecimal%e8%af%a6%e8%a7%a3%e5%92%8c%e7%b2%be%e5%ba%a6%e9%97%ae%e9%a2%98","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10006318","title":{"rendered":"BigDecimal\u8be6\u89e3\u548c\u7cbe\u5ea6\u95ee\u9898"},"content":{"rendered":"

BigDecimal<\/code> \u662f\u5927\u5382 Java \u9762\u8bd5\u5e38\u95ee\u7684\u4e00\u4e2a\u77e5\u8bc6\u70b9\u3002<\/p>\n

\u300a\u963f\u91cc\u5df4\u5df4 Java \u5f00\u53d1\u624b\u518c\u300b\u4e2d\u63d0\u5230\uff1a\u201c\u4e3a\u4e86\u907f\u514d\u7cbe\u5ea6\u4e22\u5931\uff0c\u53ef\u4ee5\u4f7f\u7528 BigDecimal<\/code> \u6765\u8fdb\u884c\u6d6e\u70b9\u6570\u7684\u8fd0\u7b97\u201d\u3002<\/p>\n

\u6d6e\u70b9\u6570\u7684\u8fd0\u7b97\u7adf\u7136\u8fd8\u4f1a\u6709\u7cbe\u5ea6\u4e22\u5931\u7684\u98ce\u9669\u5417\uff1f\u786e\u5b9e\u4f1a\uff01<\/p>\n

\u793a\u4f8b\u4ee3\u7801\uff1a<\/p>\n

float a = 2.0f - 1.9f;\nfloat b = 1.8f - 1.7f;\nSystem.out.println(a);\/\/ 0.100000024\nSystem.out.println(b);\/\/ 0.099999905\nSystem.out.println(a == b);\/\/ false<\/code><\/pre>\n
\u4e3a\u4ec0\u4e48\u6d6e\u70b9\u6570 float<\/code> \u6216 double<\/code> \u8fd0\u7b97\u7684\u65f6\u5019\u4f1a\u6709\u7cbe\u5ea6\u4e22\u5931\u7684\u98ce\u9669\u5462\uff1f<\/strong><\/p>\n
\u8fd9\u4e2a\u548c\u8ba1\u7b97\u673a\u4fdd\u5b58\u6d6e\u70b9\u6570\u7684\u673a\u5236\u6709\u5f88\u5927\u5173\u7cfb\u3002\u6211\u4eec\u77e5\u9053\u8ba1\u7b97\u673a\u662f\u4e8c\u8fdb\u5236\u7684\uff0c\u800c\u4e14\u8ba1\u7b97\u673a\u5728\u8868\u793a\u4e00\u4e2a\u6570\u5b57\u65f6\uff0c\u5bbd\u5ea6\u662f\u6709\u9650\u7684\uff0c\u65e0\u9650\u5faa\u73af\u7684\u5c0f\u6570\u5b58\u50a8\u5728\u8ba1\u7b97\u673a\u65f6\uff0c\u53ea\u80fd\u88ab\u622a\u65ad\uff0c\u6240\u4ee5\u5c31\u4f1a\u5bfc\u81f4\u5c0f\u6570\u7cbe\u5ea6\u53d1\u751f\u635f\u5931\u7684\u60c5\u51b5\u3002\u8fd9\u4e5f\u5c31\u662f\u89e3\u91ca\u4e86\u4e3a\u4ec0\u4e48\u6d6e\u70b9\u6570\u6ca1\u6709\u529e\u6cd5\u7528\u4e8c\u8fdb\u5236\u7cbe\u786e\u8868\u793a\u3002<\/p>\n
\u5c31\u6bd4\u5982\u8bf4\u5341\u8fdb\u5236\u4e0b\u7684 0.2 \u5c31\u6ca1\u529e\u6cd5\u7cbe\u786e\u8f6c\u6362\u6210\u4e8c\u8fdb\u5236\u5c0f\u6570\uff1a<\/p>\n
\/\/ 0.2 \u8f6c\u6362\u4e3a\u4e8c\u8fdb\u5236\u6570\u7684\u8fc7\u7a0b\u4e3a\uff0c\u4e0d\u65ad\u4e58\u4ee5 2\uff0c\u76f4\u5230\u4e0d\u5b58\u5728\u5c0f\u6570\u4e3a\u6b62\uff0c\n\/\/ \u5728\u8fd9\u4e2a\u8ba1\u7b97\u8fc7\u7a0b\u4e2d\uff0c\u5f97\u5230\u7684\u6574\u6570\u90e8\u5206\u4ece\u4e0a\u5230\u4e0b\u6392\u5217\u5c31\u662f\u4e8c\u8fdb\u5236\u7684\u7ed3\u679c\u3002\n0.2 * 2 = 0.4 -> 0\n0.4 * 2 = 0.8 -> 0\n0.8 * 2 = 1.6 -> 1\n0.6 * 2 = 1.2 -> 1\n0.2 * 2 = 0.4 -> 0\uff08\u53d1\u751f\u5faa\u73af\uff09\n...<\/code><\/pre>\n
\u5173\u4e8e\u6d6e\u70b9\u6570\u7684\u66f4\u591a\u5185\u5bb9\uff0c\u5efa\u8bae\u770b\u4e00\u4e0b\u8ba1\u7b97\u673a\u7cfb\u7edf\u57fa\u7840\uff08\u56db\uff09\u6d6e\u70b9\u6570<\/a>\u8fd9\u7bc7\u6587\u7ae0\u3002<\/p>\n
BigDecimal \u4ecb\u7ecd<\/h2>\n
BigDecimal<\/code> \u53ef\u4ee5\u5b9e\u73b0\u5bf9\u6d6e\u70b9\u6570\u7684\u8fd0\u7b97\uff0c\u4e0d\u4f1a\u9020\u6210\u7cbe\u5ea6\u4e22\u5931\u3002<\/p>\n
\u901a\u5e38\u60c5\u51b5\u4e0b\uff0c\u5927\u90e8\u5206\u9700\u8981\u6d6e\u70b9\u6570\u7cbe\u786e\u8fd0\u7b97\u7ed3\u679c\u7684\u4e1a\u52a1\u573a\u666f\uff08\u6bd4\u5982\u6d89\u53ca\u5230\u94b1\u7684\u573a\u666f\uff09\u90fd\u662f\u901a\u8fc7 BigDecimal<\/code> \u6765\u505a\u7684\u3002<\/p>\n
\u300a\u963f\u91cc\u5df4\u5df4 Java \u5f00\u53d1\u624b\u518c\u300b\u4e2d\u63d0\u5230\uff1a\u6d6e\u70b9\u6570\u4e4b\u95f4\u7684\u7b49\u503c\u5224\u65ad\uff0c\u57fa\u672c\u6570\u636e\u7c7b\u578b\u4e0d\u80fd\u7528 == \u6765\u6bd4\u8f83\uff0c\u5305\u88c5\u6570\u636e\u7c7b\u578b\u4e0d\u80fd\u7528 equals \u6765\u5224\u65ad\u3002<\/strong><\/p>\n
\"\"<\/p>\n
\u5177\u4f53\u539f\u56e0\u6211\u4eec\u5728\u4e0a\u9762\u5df2\u7ecf\u8be6\u7ec6\u4ecb\u7ecd\u4e86\uff0c\u8fd9\u91cc\u5c31\u4e0d\u591a\u63d0\u4e86\u3002<\/p>\n
\u60f3\u8981\u89e3\u51b3\u6d6e\u70b9\u6570\u8fd0\u7b97\u7cbe\u5ea6\u4e22\u5931\u8fd9\u4e2a\u95ee\u9898\uff0c\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528 BigDecimal<\/code> \u6765\u5b9a\u4e49\u6d6e\u70b9\u6570\u7684\u503c\uff0c\u7136\u540e\u518d\u8fdb\u884c\u6d6e\u70b9\u6570\u7684\u8fd0\u7b97\u64cd\u4f5c\u5373\u53ef\u3002<\/p>\n
BigDecimal a = new BigDecimal("1.0");\nBigDecimal b = new BigDecimal("0.9");\nBigDecimal c = new BigDecimal("0.8");\n\nBigDecimal x = a.subtract(b);\nBigDecimal y = b.subtract(c);\n\nSystem.out.println(x.compareTo(y));\/\/ 0<\/code><\/pre>\n
BigDecimal \u5e38\u89c1\u65b9\u6cd5<\/h2>\n
\u521b\u5efa<\/h3>\n
\u6211\u4eec\u5728\u4f7f\u7528 BigDecimal<\/code> \u65f6\uff0c\u4e3a\u4e86\u9632\u6b62\u7cbe\u5ea6\u4e22\u5931\uff0c\u63a8\u8350\u4f7f\u7528\u5b83\u7684BigDecimal(String val)<\/code>\u6784\u9020\u65b9\u6cd5\u6216\u8005 BigDecimal.valueOf(double val)<\/code> \u9759\u6001\u65b9\u6cd5\u6765\u521b\u5efa\u5bf9\u8c61\u3002<\/p>\n
\u300a\u963f\u91cc\u5df4\u5df4 Java \u5f00\u53d1\u624b\u518c\u300b\u5bf9\u8fd9\u90e8\u5206\u5185\u5bb9\u4e5f\u6709\u63d0\u5230\uff0c\u5982\u4e0b\u56fe\u6240\u793a\u3002<\/p>\n
\"\"<\/p>\n
\u52a0\u51cf\u4e58\u9664<\/h3>\n
add<\/code> \u65b9\u6cd5\u7528\u4e8e\u5c06\u4e24\u4e2a BigDecimal<\/code> \u5bf9\u8c61\u76f8\u52a0\uff0csubtract<\/code> \u65b9\u6cd5\u7528\u4e8e\u5c06\u4e24\u4e2a BigDecimal<\/code> \u5bf9\u8c61\u76f8\u51cf\u3002multiply<\/code> \u65b9\u6cd5\u7528\u4e8e\u5c06\u4e24\u4e2a BigDecimal<\/code> \u5bf9\u8c61\u76f8\u4e58\uff0cdivide<\/code> \u65b9\u6cd5\u7528\u4e8e\u5c06\u4e24\u4e2a BigDecimal<\/code> \u5bf9\u8c61\u76f8\u9664\u3002<\/p>\n
BigDecimal a = new BigDecimal("1.0");\nBigDecimal b = new BigDecimal("0.9");\nSystem.out.println(a.add(b));\/\/ 1.9\nSystem.out.println(a.subtract(b));\/\/ 0.1\nSystem.out.println(a.multiply(b));\/\/ 0.90\nSystem.out.println(a.divide(b));\/\/ \u65e0\u6cd5\u9664\u5c3d\uff0c\u629b\u51fa ArithmeticException \u5f02\u5e38\nSystem.out.println(a.divide(b, 2, RoundingMode.HALF_UP));\/\/ 1.11<\/code><\/pre>\n
\u8fd9\u91cc\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5728\u6211\u4eec\u4f7f\u7528 divide<\/code> \u65b9\u6cd5\u7684\u65f6\u5019\u5c3d\u91cf\u4f7f\u7528 3 \u4e2a\u53c2\u6570\u7248\u672c\uff0c\u5e76\u4e14RoundingMode<\/code> \u4e0d\u8981\u9009\u62e9 UNNECESSARY<\/code>\uff0c\u5426\u5219\u5f88\u53ef\u80fd\u4f1a\u9047\u5230 ArithmeticException<\/code>\uff08\u65e0\u6cd5\u9664\u5c3d\u51fa\u73b0\u65e0\u9650\u5faa\u73af\u5c0f\u6570\u7684\u65f6\u5019\uff09\uff0c\u5176\u4e2d scale<\/code> \u8868\u793a\u8981\u4fdd\u7559\u51e0\u4f4d\u5c0f\u6570\uff0croundingMode<\/code> \u4ee3\u8868\u4fdd\u7559\u89c4\u5219\u3002<\/p>\n
public BigDecimal divide(BigDecimal divisor, int scale, RoundingMode roundingMode) {\n    return divide(divisor, scale, roundingMode.oldMode);\n}<\/code><\/pre>\n
\u4fdd\u7559\u89c4\u5219\u975e\u5e38\u591a\uff0c\u8fd9\u91cc\u5217\u4e3e\u51e0\u79cd:<\/p>\n
public enum RoundingMode {\n   \/\/ 2.5 -> 3 , 1.6 -> 2\n   \/\/ -1.6 -> -2 , -2.5 -> -3\n             UP(BigDecimal.ROUND_UP),\n   \/\/ 2.5 -> 2 , 1.6 -> 1\n   \/\/ -1.6 -> -1 , -2.5 -> -2\n             DOWN(BigDecimal.ROUND_DOWN),\n             \/\/ 2.5 -> 3 , 1.6 -> 2\n   \/\/ -1.6 -> -1 , -2.5 -> -2\n             CEILING(BigDecimal.ROUND_CEILING),\n             \/\/ 2.5 -> 2 , 1.6 -> 1\n   \/\/ -1.6 -> -2 , -2.5 -> -3\n             FLOOR(BigDecimal.ROUND_FLOOR),\n       \/\/ 2.5 -> 3 , 1.6 -> 2\n   \/\/ -1.6 -> -2 , -2.5 -> -3\n             HALF_UP(BigDecimal.ROUND_HALF_UP),\n   \/\/......\n}<\/code><\/pre>\n
\u5927\u5c0f\u6bd4\u8f83<\/h3>\n
a.compareTo(b)<\/code> : \u8fd4\u56de -1 \u8868\u793a a<\/code> \u5c0f\u4e8e b<\/code>\uff0c0 \u8868\u793a a<\/code> \u7b49\u4e8e b<\/code> \uff0c 1 \u8868\u793a a<\/code> \u5927\u4e8e b<\/code>\u3002<\/p>\n
BigDecimal a = new BigDecimal("1.0");\nBigDecimal b = new BigDecimal("0.9");\nSystem.out.println(a.compareTo(b));\/\/ 1<\/code><\/pre>\n
\u4fdd\u7559\u51e0\u4f4d\u5c0f\u6570<\/h3>\n
\u901a\u8fc7 setScale<\/code>\u65b9\u6cd5\u8bbe\u7f6e\u4fdd\u7559\u51e0\u4f4d\u5c0f\u6570\u4ee5\u53ca\u4fdd\u7559\u89c4\u5219\u3002\u4fdd\u7559\u89c4\u5219\u6709\u633a\u591a\u79cd\uff0c\u4e0d\u9700\u8981\u8bb0\uff0cIDEA \u4f1a\u63d0\u793a\u3002<\/p>\n
BigDecimal m = new BigDecimal("1.255433");\nBigDecimal n = m.setScale(3,RoundingMode.HALF_DOWN);\nSystem.out.println(n);\/\/ 1.255<\/code><\/pre>\n
BigDecimal \u7b49\u503c\u6bd4\u8f83\u95ee\u9898<\/h2>\n
\u300a\u963f\u91cc\u5df4\u5df4 Java \u5f00\u53d1\u624b\u518c\u300b\u4e2d\u63d0\u5230\uff1a<\/p>\n
\"\"<\/p>\n
BigDecimal<\/code> \u4f7f\u7528 equals()<\/code> \u65b9\u6cd5\u8fdb\u884c\u7b49\u503c\u6bd4\u8f83\u51fa\u73b0\u95ee\u9898\u7684\u4ee3\u7801\u793a\u4f8b\uff1a<\/p>\n
BigDecimal a = new BigDecimal("1");\nBigDecimal b = new BigDecimal("1.0");\nSystem.out.println(a.equals(b));\/\/false<\/code><\/pre>\n
\u8fd9\u662f\u56e0\u4e3a equals()<\/code> \u65b9\u6cd5\u4e0d\u4ec5\u4ec5\u4f1a\u6bd4\u8f83\u503c\u7684\u5927\u5c0f\uff08value\uff09\u8fd8\u4f1a\u6bd4\u8f83\u7cbe\u5ea6\uff08scale\uff09\uff0c\u800c compareTo()<\/code> \u65b9\u6cd5\u6bd4\u8f83\u7684\u65f6\u5019\u4f1a\u5ffd\u7565\u7cbe\u5ea6\u3002<\/p>\n
1.0 \u7684 scale \u662f 1\uff0c1 \u7684 scale \u662f 0\uff0c\u56e0\u6b64 a.equals(b)<\/code> \u7684\u7ed3\u679c\u662f false\u3002<\/p>\n
\"\"<\/p>\n
compareTo()<\/code> \u65b9\u6cd5\u53ef\u4ee5\u6bd4\u8f83\u4e24\u4e2a BigDecimal<\/code> \u7684\u503c\uff0c\u5982\u679c\u76f8\u7b49\u5c31\u8fd4\u56de 0\uff0c\u5982\u679c\u7b2c 1 \u4e2a\u6570\u6bd4\u7b2c 2 \u4e2a\u6570\u5927\u5219\u8fd4\u56de 1\uff0c\u53cd\u4e4b\u8fd4\u56de-1\u3002<\/p>\n
BigDecimal a = new BigDecimal("1");\nBigDecimal b = new BigDecimal("1.0");\nSystem.out.println(a.compareTo(b));\/\/0<\/code><\/pre>\n
\u603b\u7ed3<\/h2>\n
\u6d6e\u70b9\u6570\u6ca1\u6709\u529e\u6cd5\u7528\u4e8c\u8fdb\u5236\u7cbe\u786e\u8868\u793a\uff0c\u56e0\u6b64\u5b58\u5728\u7cbe\u5ea6\u4e22\u5931\u7684\u98ce\u9669\u3002<\/p>\n
\u4e0d\u8fc7\uff0cJava \u63d0\u4f9b\u4e86BigDecimal<\/code> \u6765\u64cd\u4f5c\u6d6e\u70b9\u6570\u3002BigDecimal<\/code> \u7684\u5b9e\u73b0\u5229\u7528\u5230\u4e86 BigInteger<\/code> \uff08\u7528\u6765\u64cd\u4f5c\u5927\u6574\u6570\uff09, \u6240\u4e0d\u540c\u7684\u662f BigDecimal<\/code> \u52a0\u5165\u4e86\u5c0f\u6570\u4f4d\u7684\u6982\u5ff5\u3002<\/p>\n
https:\/\/segmentfault.com\/a\/1190000042377516<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
BigDecimal \u662f\u5927\u5382 Java \u9762\u8bd5\u5e38\u95ee\u7684\u4e00\u4e2a\u77e5\u8bc6\u70b9\u3002 \u300a\u963f\u91cc\u5df4\u5df4 Java \u5f00\u53d1\u624b\u518c\u300b\u4e2d\u63d0\u5230\uff1a\u201c\u4e3a\u4e86 […]<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[],"tags":[],"class_list":["post-10006318","post","type-post","status-publish","format-standard","hentry"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10006318","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10006318"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10006318\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10006318"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10006318"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10006318"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}