http:\/\/blog.csdn.net\/AYellow\/archive\/2003\/03\/11\/7398.aspx<\/p>\n
\u95ee\u9898\u7684\u63d0\u51fa\uff1a<\/p>\n
\u5982\u679c\u6211\u4eec\u7f16\u8bd1\u8fd0\u884c\u4e0b\u9762\u8fd9\u4e2a\u7a0b\u5e8f\u4f1a\u770b\u5230\u4ec0\u4e48\uff1f<\/p>\n
public class Test{<\/p>\n
public static void main(String args[]){<\/p>\n
System.out.println(0.05+0.01);<\/p>\n
System.out.println(1.0-0.42);<\/p>\n
System.out.println(4.015*100);<\/p>\n
System.out.println(123.3\/100);<\/p>\n
}<\/p>\n
};<\/p>\n
\u4f60\u6ca1\u6709\u770b\u9519\uff01\u7ed3\u679c\u786e\u5b9e\u662f<\/p>\n
0.060000000000000005<\/p>\n
0.5800000000000001<\/p>\n
401.49999999999994<\/p>\n
1.2329999999999999<\/p>\n
Java\u4e2d\u7684\u7b80\u5355\u6d6e\u70b9\u6570\u7c7b\u578bfloat\u548cdouble\u4e0d\u80fd\u591f\u8fdb\u884c\u8fd0\u7b97\u3002\u4e0d\u5149\u662fJava\uff0c\u5728\u5176\u5b83\u5f88\u591a\u7f16\u7a0b\u8bed\u8a00\u4e2d\u4e5f\u6709\u8fd9\u6837\u7684\u95ee\u9898\u3002\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u8ba1\u7b97\u7684\u7ed3\u679c\u662f\u51c6\u786e\u7684\uff0c\u4f46\u662f\u591a\u8bd5\u51e0\u6b21\uff08\u53ef\u4ee5\u505a\u4e00\u4e2a\u5faa\u73af\uff09\u5c31\u53ef\u4ee5\u8bd5\u51fa\u7c7b\u4f3c\u4e0a\u9762\u7684\u9519\u8bef\u3002\u73b0\u5728\u7ec8\u4e8e\u7406\u89e3\u4e3a\u4ec0\u4e48\u8981\u6709BCD\u7801\u4e86\u3002<\/p>\n
\u8fd9\u4e2a\u95ee\u9898\u76f8\u5f53\u4e25\u91cd\uff0c\u5982\u679c\u4f60\u67099.999999999999\u5143\uff0c\u4f60\u7684\u8ba1\u7b97\u673a\u662f\u4e0d\u4f1a\u8ba4\u4e3a\u4f60\u53ef\u4ee5\u8d2d\u4e7010\u5143\u7684\u5546\u54c1\u7684\u3002<\/p>\n
\u5728\u6709\u7684\u7f16\u7a0b\u8bed\u8a00\u4e2d\u63d0\u4f9b\u4e86\u4e13\u95e8\u7684\u8d27\u5e01\u7c7b\u578b\u6765\u5904\u7406\u8fd9\u79cd\u60c5\u51b5\uff0c\u4f46\u662fJava\u6ca1\u6709\u3002\u73b0\u5728\u8ba9\u6211\u4eec\u770b\u770b\u5982\u4f55\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n
\u56db\u820d\u4e94\u5165<\/p>\n
\u6211\u4eec\u7684\u7b2c\u4e00\u4e2a\u53cd\u5e94\u662f\u505a\u56db\u820d\u4e94\u5165\u3002Math\u7c7b\u4e2d\u7684round\u65b9\u6cd5\u4e0d\u80fd\u8bbe\u7f6e\u4fdd\u7559\u51e0\u4f4d\u5c0f\u6570\uff0c\u6211\u4eec\u53ea\u80fd\u8c61\u8fd9\u6837\uff08\u4fdd\u7559\u4e24\u4f4d\uff09\uff1a<\/p>\n
public double round(double value){<\/p>\n
return Math.round(value*100)\/100.0;<\/p>\n
}<\/p>\n
\u975e\u5e38\u4e0d\u5e78\uff0c\u4e0a\u9762\u7684\u4ee3\u7801\u5e76\u4e0d\u80fd\u6b63\u5e38\u5de5\u4f5c\uff0c\u7ed9\u8fd9\u4e2a\u65b9\u6cd5\u4f20\u51654.015\u5b83\u5c06\u8fd4\u56de4.01\u800c\u4e0d\u662f4.02\uff0c\u5982\u6211\u4eec\u5728\u4e0a\u9762\u770b\u5230\u7684<\/p>\n
4.015*100=401.49999999999994<\/p>\n
\u56e0\u6b64\u5982\u679c\u6211\u4eec\u8981\u505a\u5230\u7cbe\u786e\u7684\u56db\u820d\u4e94\u5165\uff0c\u4e0d\u80fd\u5229\u7528\u7b80\u5355\u7c7b\u578b\u505a\u4efb\u4f55\u8fd0\u7b97<\/p>\n
java.text.DecimalFormat\u4e5f\u4e0d\u80fd\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff1a<\/p>\n
System.out.println(new java.text.DecimalFormat(“0.00”).format(4.025));<\/p>\n
\u8f93\u51fa\u662f4.02<\/p>\n
BigDecimal
\n\u5728\u300aEffective Java\u300b\u8fd9\u672c\u4e66\u4e2d\u4e5f\u63d0\u5230\u8fd9\u4e2a\u539f\u5219\uff0cfloat\u548cdouble\u53ea\u80fd\u7528\u6765\u505a\u79d1\u5b66\u8ba1\u7b97\u6216\u8005\u662f\u5de5\u7a0b\u8ba1\u7b97\uff0c\u5728\u5546\u4e1a\u8ba1\u7b97\u4e2d\u6211\u4eec\u8981\u7528java.math.BigDecimal\u3002BigDecimal\u4e00\u5171\u67094\u4e2a\u591f\u9020\u65b9\u6cd5\uff0c\u6211\u4eec\u4e0d\u5173\u5fc3\u7528BigInteger\u6765\u591f\u9020\u7684\u90a3\u4e24\u4e2a\uff0c\u90a3\u4e48\u8fd8\u6709\u4e24\u4e2a\uff0c\u5b83\u4eec\u662f\uff1a<\/p>\n
BigDecimal(double val)<\/p>\n
Translates a double into a BigDecimal.<\/p>\n
BigDecimal(String val)<\/p>\n
Translates the String repre sentation of a BigDecimal into a BigDecimal.<\/p>\n
\u4e0a\u9762\u7684API\u7b80\u8981\u63cf\u8ff0\u76f8\u5f53\u7684\u660e\u786e\uff0c\u800c\u4e14\u901a\u5e38\u60c5\u51b5\u4e0b\uff0c\u4e0a\u9762\u7684\u90a3\u4e00\u4e2a\u4f7f\u7528\u8d77\u6765\u8981\u65b9\u4fbf\u4e00\u4e9b\u3002\u6211\u4eec\u53ef\u80fd\u60f3\u90fd\u4e0d\u60f3\u5c31\u7528\u4e0a\u4e86\uff0c\u4f1a\u6709\u4ec0\u4e48\u95ee\u9898\u5462\uff1f\u7b49\u5230\u51fa\u4e86\u95ee\u9898\u7684\u65f6\u5019\uff0c\u624d\u53d1\u73b0\u4e0a\u9762\u54ea\u4e2a\u591f\u9020\u65b9\u6cd5\u7684\u8be6\u7ec6\u8bf4\u660e\u4e2d\u6709\u8fd9\u4e48\u4e00\u6bb5\uff1a<\/p>\n
Note: the results of this constructor can be somewhat unpredictable. One might assume that new BigDecimal(.1) is exactly equal to .1, but it is actually equal to .1000000000000000055511151231257827021181583404541015625. This is so because .1 cannot be represented exactly as a double (or, for that matter, as a binary fraction of any finite length). Thus, the long value that is being passed in to the constructor is not exactly equal to .1, appearances nonwithstanding.<\/p>\n
The (String) constructor, on the other hand, is perfectly predictable: new BigDecimal(“.1”) is exactly equal to .1, as one would expect. Therefore, it is generally recommended that the (String) constructor be used in preference to this one.<\/p>\n
\u539f\u6765\u6211\u4eec\u5982\u679c\u9700\u8981\u7cbe\u786e\u8ba1\u7b97\uff0c\u975e\u8981\u7528String\u6765\u591f\u9020BigDecimal\u4e0d\u53ef\uff01\u5728\u300aEffective Java\u300b\u4e00\u4e66\u4e2d\u7684\u4f8b\u5b50\u662f\u7528String\u6765\u591f\u9020BigDecimal\u7684\uff0c\u4f46\u662f\u4e66\u4e0a\u5374\u6ca1\u6709\u5f3a\u8c03\u8fd9\u4e00\u70b9\uff0c\u8fd9\u4e5f\u8bb8\u662f\u4e00\u4e2a\u5c0f\u5c0f\u7684\u5931\u8bef\u5427\u3002<\/p>\n
\u89e3\u51b3\u65b9\u6848<\/p>\n
\u73b0\u5728\u6211\u4eec\u5df2\u7ecf\u53ef\u4ee5\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u4e86\uff0c\u539f\u5219\u662f\u4f7f\u7528BigDecimal\u5e76\u4e14\u4e00\u5b9a\u8981\u7528String\u6765\u591f\u9020\u3002<\/p>\n
\u4f46\u662f\u60f3\u50cf\u4e00\u4e0b\u5427\uff0c\u5982\u679c\u6211\u4eec\u8981\u505a\u4e00\u4e2a\u52a0\u6cd5\u8fd0\u7b97\uff0c\u9700\u8981\u5148\u5c06\u4e24\u4e2a\u6d6e\u70b9\u6570\u8f6c\u4e3aString\uff0c\u7136\u540e\u591f\u9020\u6210BigDecimal\uff0c\u5728\u5176\u4e2d\u4e00\u4e2a\u4e0a\u8c03\u7528add\u65b9\u6cd5\uff0c\u4f20\u5165\u53e6\u4e00\u4e2a\u4f5c\u4e3a\u53c2\u6570\uff0c\u7136\u540e\u628a\u8fd0\u7b97\u7684\u7ed3\u679c\uff08BigDecimal\uff09\u518d\u8f6c\u6362\u4e3a\u6d6e\u70b9\u6570\u3002\u4f60\u80fd\u591f\u5fcd\u53d7\u8fd9\u4e48\u70e6\u7410\u7684\u8fc7\u7a0b\u5417\uff1f\u4e0b\u9762\u6211\u4eec\u63d0\u4f9b\u4e00\u4e2a\u5de5\u5177\u7c7bArith\u6765\u7b80\u5316\u64cd\u4f5c\u3002\u5b83\u63d0\u4f9b\u4ee5\u4e0b\u9759\u6001\u65b9\u6cd5\uff0c\u5305\u62ec\u52a0\u51cf\u4e58\u9664\u548c\u56db\u820d\u4e94\u5165\uff1a<\/p>\n
public static double add(double v1,double v2)<\/p>\n
public static double sub(double v1,double v2)<\/p>\n
public static double mul(double v1,double v2)<\/p>\n
public static double div(double v1,double v2)<\/p>\n
public static double div(double v1,double v2,int scale)<\/p>\n
public static double round(double v,int scale)<\/p>\n
\u9644\u5f55<\/p>\n
\u6e90\u6587\u4ef6Arith.java\uff1a<\/p>\n
import java.math.BigDecimal;<\/p>\n
\/**<\/p>\n
* \u7531\u4e8eJava\u7684\u7b80\u5355\u7c7b\u578b\u4e0d\u80fd\u591f\u7cbe\u786e\u7684\u5bf9\u6d6e\u70b9\u6570\u8fdb\u884c\u8fd0\u7b97\uff0c\u8fd9\u4e2a\u5de5\u5177\u7c7b\u63d0\u4f9b\u7cbe<\/p>\n
* \u786e\u7684\u6d6e\u70b9\u6570\u8fd0\u7b97\uff0c\u5305\u62ec\u52a0\u51cf\u4e58\u9664\u548c\u56db\u820d\u4e94\u5165\u3002<\/p>\n
*\/<\/p>\n
public class Arith{<\/p>\n
\/\/\u9ed8\u8ba4\u9664\u6cd5\u8fd0\u7b97\u7cbe\u5ea6<\/p>\n
private static final int DEF_DIV_SCALE = 10;<\/p>\n
\/\/\u8fd9\u4e2a\u7c7b\u4e0d\u80fd\u5b9e\u4f8b\u5316<\/p>\n
private Arith(){<\/p>\n
}<\/p>\n
\/**<\/p>\n
* \u63d0\u4f9b\u7cbe\u786e\u7684\u52a0\u6cd5\u8fd0\u7b97\u3002<\/p>\n
* @param v1 \u88ab\u52a0\u6570<\/p>\n
* @param v2 \u52a0\u6570<\/p>\n
* @return \u4e24\u4e2a\u53c2\u6570\u7684\u548c<\/p>\n
*\/<\/p>\n
public static double add(double v1,double v2){<\/p>\n
BigDecimal b1 = new BigDecimal(Double.toString(v1));<\/p>\n
BigDecimal b2 = new BigDecimal(Double.toString(v2));<\/p>\n
return b1.add(b2).doubleValue();<\/p>\n
}<\/p>\n
\/**<\/p>\n
* \u63d0\u4f9b\u7cbe\u786e\u7684\u51cf\u6cd5\u8fd0\u7b97\u3002<\/p>\n
* @param v1 \u88ab\u51cf\u6570<\/p>\n
* @param v2 \u51cf\u6570<\/p>\n
* @return \u4e24\u4e2a\u53c2\u6570\u7684\u5dee<\/p>\n
*\/<\/p>\n
public static double sub(double v1,double v2){<\/p>\n
BigDecimal b1 = new BigDecimal(Double.toString(v1));<\/p>\n
BigDecimal b2 = new BigDecimal(Double.toString(v2));<\/p>\n
return b1.subtract(b2).doubleValue();<\/p>\n
}<\/p>\n
\/**<\/p>\n
* \u63d0\u4f9b\u7cbe\u786e\u7684\u4e58\u6cd5\u8fd0\u7b97\u3002<\/p>\n
* @param v1 \u88ab\u4e58\u6570<\/p>\n
* @param v2 \u4e58\u6570<\/p>\n
* @return \u4e24\u4e2a\u53c2\u6570\u7684\u79ef<\/p>\n
*\/<\/p>\n
public static double mul(double v1,double v2){<\/p>\n
BigDecimal b1 = new BigDecimal(Double.toString(v1));<\/p>\n
BigDecimal b2 = new BigDecimal(Double.toString(v2));<\/p>\n
return b1.multiply(b2).doubleValue();<\/p>\n
}<\/p>\n
\/**<\/p>\n
* \u63d0\u4f9b\uff08\u76f8\u5bf9\uff09\u7cbe\u786e\u7684\u9664\u6cd5\u8fd0\u7b97\uff0c\u5f53\u53d1\u751f\u9664\u4e0d\u5c3d\u7684\u60c5\u51b5\u65f6\uff0c\u7cbe\u786e\u5230<\/p>\n
* \u5c0f\u6570\u70b9\u4ee5\u540e10\u4f4d\uff0c\u4ee5\u540e\u7684\u6570\u5b57\u56db\u820d\u4e94\u5165\u3002<\/p>\n
* @param v1 \u88ab\u9664\u6570<\/p>\n
* @param v2 \u9664\u6570<\/p>\n
* @return \u4e24\u4e2a\u53c2\u6570\u7684\u5546<\/p>\n
*\/<\/p>\n
public static double div(double v1,double v2){<\/p>\n
return div(v1,v2,DEF_DIV_SCALE);<\/p>\n
}<\/p>\n
\/**<\/p>\n
* \u63d0\u4f9b\uff08\u76f8\u5bf9\uff09\u7cbe\u786e\u7684\u9664\u6cd5\u8fd0\u7b97\u3002\u5f53\u53d1\u751f\u9664\u4e0d\u5c3d\u7684\u60c5\u51b5\u65f6\uff0c\u7531scale\u53c2\u6570\u6307<\/p>\n
* \u5b9a\u7cbe\u5ea6\uff0c\u4ee5\u540e\u7684\u6570\u5b57\u56db\u820d\u4e94\u5165\u3002<\/p>\n
* @param v1 \u88ab\u9664\u6570<\/p>\n
* @param v2 \u9664\u6570<\/p>\n
* @param scale \u8868\u793a\u8868\u793a\u9700\u8981\u7cbe\u786e\u5230\u5c0f\u6570\u70b9\u4ee5\u540e\u51e0\u4f4d\u3002<\/p>\n
* @return \u4e24\u4e2a\u53c2\u6570\u7684\u5546<\/p>\n
*\/<\/p>\n
public static double div(double v1,double v2,int scale){<\/p>\n
if(scale<0){\n\nthrow new IllegalArgumentException(\n\n\"The scale must be a positive integer or zero\");\n\n}\n\nBigDecimal b1 = new BigDecimal(Double.toString(v1));\n\nBigDecimal b2 = new BigDecimal(Double.toString(v2));\n\nreturn b1.divide(b2,scale,BigDecimal.ROUND_HALF_UP).doubleValue();\n\n}\n\n\n\n\/**\n\n* \u63d0\u4f9b\u7cbe\u786e\u7684\u5c0f\u6570\u4f4d\u56db\u820d\u4e94\u5165\u5904\u7406\u3002\n\n* @param v \u9700\u8981\u56db\u820d\u4e94\u5165\u7684\u6570\u5b57\n\n* @param scale \u5c0f\u6570\u70b9\u540e\u4fdd\u7559\u51e0\u4f4d\n\n* @return \u56db\u820d\u4e94\u5165\u540e\u7684\u7ed3\u679c\n\n*\/\n\npublic static double round(double v,int scale){\n\nif(scale<0){\n\nthrow new IllegalArgumentException(\n\n\"The scale must be a positive integer or zero\");\n\n}\n\nBigDecimal b = new BigDecimal(Double.toString(v));\n\nBigDecimal one = new BigDecimal(\"1\");\n\nreturn b.divide(one,scale,BigDecimal.ROUND_HALF_UP).doubleValue();\n\n}\n\n};\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"
http:\/\/blog.csdn.net\/AYellow\/archive\/2003\/03\/11\/7398.aspx \u95ee\u9898\u7684\u63d0\u51fa\uff1a \u5982\u679c\u6211\u4eec\u7f16\u8bd1\u8fd0\u884c\u4e0b\u9762\u8fd9\u4e2a\u7a0b\u5e8f\u4f1a\u770b\u5230\u4ec0\u4e48\uff1f public class T… <\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[28],"tags":[],"class_list":["post-90","post","type-post","status-publish","format-standard","hentry","category-computer"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=\/wp\/v2\/posts\/90","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=90"}],"version-history":[{"count":0,"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=\/wp\/v2\/posts\/90\/revisions"}],"wp:attachment":[{"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=90"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=90"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/opgogo.com\/blog2\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=90"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}