......
]]>
闂鐨勬彁鍑猴細
濡傛灉鎴戜滑緙栬瘧榪愯涓嬮潰榪欎釜紼嬪簭浼氱湅鍒頒粈涔堬紵
public class Test{
public static void main(String args[]){
System.out.println(0.05+0.01);
System.out.println(1.0-0.42);
System.out.println(4.015*100);
System.out.println(123.3/100);
}
};
浣犳病鏈夌湅閿欙紒緇撴灉紜疄鏄?br /> 0.060000000000000005
0.5800000000000001
401.49999999999994
1.2329999999999999
Java涓殑綆鍗曟誕鐐規(guī)暟綾誨瀷float鍜宒ouble涓嶈兘澶熻繘琛岃繍綆椼備笉鍏夋槸Java錛屽湪鍏跺畠寰堝緙栫▼璇█涓篃鏈夎繖鏍風(fēng)殑闂銆傚湪澶у鏁版儏鍐典笅錛岃綆楃殑緇撴灉鏄噯紜殑錛屼絾鏄璇曞嚑嬈★紙鍙互鍋氫竴涓驚鐜級灝卞彲浠ヨ瘯鍑虹被浼間笂闈㈢殑閿欒銆傜幇鍦ㄧ粓浜庣悊瑙ｄ負浠涔堣鏈塀CD鐮佷簡銆?br /> 榪欎釜闂鐩稿綋涓ラ噸錛屽鏋滀綘鏈?.999999999999鍏冿紝浣犵殑璁＄畻鏈烘槸涓嶄細璁や負浣犲彲浠ヨ喘涔?0鍏冪殑鍟嗗搧鐨勩?br /> 鍦ㄦ湁鐨勭紪紼嬭璦涓彁渚涗簡涓撻棬鐨勮揣甯佺被鍨嬫潵澶勭悊榪欑鎯呭喌錛屼絾鏄疛ava娌℃湁銆傜幇鍦ㄨ鎴戜滑鐪嬬湅濡備綍瑙ｅ喅榪欎釜闂銆?br />
鍥涜垗浜斿叆
鎴戜滑鐨勭涓涓弽搴旀槸鍋氬洓鑸嶄簲鍏ャ侻ath綾諱腑鐨剅ound鏂規(guī)硶涓嶈兘璁劇疆淇濈暀鍑犱綅灝忔暟錛屾垜浠彧鑳借薄榪欐牱錛堜繚鐣欎袱浣嶏級錛?br /> public double round(double value){
return Math.round(value*100)/100.0;
}
闈炲父涓嶅垢錛屼笂闈㈢殑浠ｇ爜騫朵笉鑳芥甯稿伐浣滐紝緇欒繖涓柟娉曚紶鍏?.015瀹冨皢榪斿洖4.01鑰屼笉鏄?.02錛屽鎴戜滑鍦ㄤ笂闈㈢湅鍒扮殑
4.015*100=401.49999999999994
鍥犳濡傛灉鎴戜滑瑕佸仛鍒扮簿紜殑鍥涜垗浜斿叆錛屼笉鑳藉埄鐢ㄧ畝鍗曠被鍨嬪仛浠諱綍榪愮畻
java.text.DecimalFormat涔熶笉鑳借В鍐寵繖涓棶棰橈細
System.out.println(new java.text.DecimalFormat("0.00").format(4.025));
杈撳嚭鏄?.02
BigDecimal
鍦ㄣ奅ffective Java銆嬭繖鏈功涓篃鎻愬埌榪欎釜鍘熷垯錛宖loat鍜宒ouble鍙兘鐢ㄦ潵鍋氱瀛﹁綆楁垨鑰呮槸宸ョ▼璁＄畻錛屽湪鍟嗕笟璁＄畻涓垜浠鐢╦ava.math.BigDecimal銆侭igDecimal涓鍏辨湁4涓閫犳柟娉曪紝鎴戜滑涓嶅叧蹇冪敤BigInteger鏉ュ閫犵殑閭ｄ袱涓紝閭ｄ箞榪樻湁涓や釜錛屽畠浠槸錛?br /> BigDecimal(double val)
Translates a double into a BigDecimal.
BigDecimal(String val)
Translates the String repre sentation of a BigDecimal into a BigDecimal.
涓婇潰鐨凙PI綆瑕佹弿榪扮浉褰撶殑鏄庣‘錛岃屼笖閫氬父鎯呭喌涓嬶紝涓婇潰鐨勯偅涓涓嬌鐢ㄨ搗鏉ヨ鏂逛究涓浜涖傛垜浠彲鑳芥兂閮戒笉鎯沖氨鐢ㄤ笂浜嗭紝浼氭湁浠涔堥棶棰樺憿錛熺瓑鍒板嚭浜嗛棶棰樼殑鏃跺欙紝鎵嶅彂鐜頒笂闈㈠摢涓閫犳柟娉曠殑璇︾粏璇存槑涓湁榪欎箞涓孌碉細
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.
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.
鍘熸潵鎴戜滑濡傛灉闇瑕佺簿紜綆楋紝闈炶鐢⊿tring鏉ュ閫燘igDecimal涓嶅彲錛佸湪銆奅ffective Java銆嬩竴涔︿腑鐨勪緥瀛愭槸鐢⊿tring鏉ュ閫燘igDecimal鐨勶紝浣嗘槸涔︿笂鍗存病鏈夊己璋冭繖涓鐐癸紝榪欎篃璁告槸涓涓皬灝忕殑澶辮鍚с?br />
瑙ｅ喅鏂規(guī)
鐜板湪鎴戜滑宸茬粡鍙互瑙ｅ喅榪欎釜闂浜嗭紝鍘熷垯鏄嬌鐢˙igDecimal騫朵笖涓瀹氳鐢⊿tring鏉ュ閫犮?br /> 浣嗘槸鎯沖儚涓涓嬪惂錛屽鏋滄垜浠鍋氫竴涓姞娉曡繍綆楋紝闇瑕佸厛灝嗕袱涓誕鐐規(guī)暟杞負String錛岀劧鍚庡閫犳垚BigDecimal錛屽湪鍏朵腑涓涓笂璋冪敤add鏂規(guī)硶錛屼紶鍏ュ彟涓涓綔涓哄弬鏁幫紝鐒跺悗鎶婅繍綆楃殑緇撴灉錛圔igDecimal錛夊啀杞崲涓烘誕鐐規(guī)暟銆備綘鑳藉蹇嶅彈榪欎箞鐑︾悙鐨勮繃紼嬪悧錛熶笅闈㈡垜浠彁渚涗竴涓伐鍏風(fēng)被Arith鏉ョ畝鍖栨搷浣溿傚畠鎻愪緵浠ヤ笅闈欐佹柟娉曪紝鍖呮嫭鍔犲噺涔橀櫎鍜屽洓鑸嶄簲鍏ワ細
public static double add(double v1,double v2)
public static double sub(double v1,double v2)
public static double mul(double v1,double v2)
public static double div(double v1,double v2)
public static double div(double v1,double v2,int scale)
public static double round(double v,int scale)
闄勫綍
婧愭枃浠禔rith.java錛?br /> import java.math.BigDecimal;
/**
* 鐢變簬Java鐨勭畝鍗曠被鍨嬩笉鑳藉綺劇‘鐨勫嫻偣鏁拌繘琛岃繍綆楋紝榪欎釜宸ュ叿綾繪彁渚涚簿
* 紜殑嫻偣鏁拌繍綆楋紝鍖呮嫭鍔犲噺涔橀櫎鍜屽洓鑸嶄簲鍏ャ?br /> */
public class Arith{
//榛樿闄ゆ硶榪愮畻綺懼害
private static final int DEF_DIV_SCALE = 10;
//榪欎釜綾諱笉鑳藉疄渚嬪寲
private Arith(){
}
/**
* 鎻愪緵綺劇‘鐨勫姞娉曡繍綆椼?br /> * @param v1 琚姞鏁?br /> * @param v2 鍔犳暟
* @return 涓や釜鍙傛暟鐨勫拰
*/
public static double add(double v1,double v2){
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.add(b2).doubleValue();
}
/**
* 鎻愪緵綺劇‘鐨勫噺娉曡繍綆椼?br /> * @param v1 琚噺鏁?br /> * @param v2 鍑忔暟
* @return 涓や釜鍙傛暟鐨勫樊
*/
public static double sub(double v1,double v2){
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.subtract(b2).doubleValue();
}
/**
* 鎻愪緵綺劇‘鐨勪箻娉曡繍綆椼?br /> * @param v1 琚箻鏁?br /> * @param v2 涔樻暟
* @return 涓や釜鍙傛暟鐨勭Н
*/
public static double mul(double v1,double v2){
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.multiply(b2).doubleValue();
}
/**
* 鎻愪緵錛堢浉瀵癸級綺劇‘鐨勯櫎娉曡繍綆楋紝褰撳彂鐢熼櫎涓嶅敖鐨勬儏鍐墊椂錛岀簿紜埌
* 灝忔暟鐐逛互鍚?0浣嶏紝浠ュ悗鐨勬暟瀛楀洓鑸嶄簲鍏ャ?br /> * @param v1 琚櫎鏁?br /> * @param v2 闄ゆ暟
* @return 涓や釜鍙傛暟鐨勫晢
*/
public static double div(double v1,double v2){
return div(v1,v2,DEF_DIV_SCALE);
}
/**
* 鎻愪緵錛堢浉瀵癸級綺劇‘鐨勯櫎娉曡繍綆椼傚綋鍙戠敓闄や笉灝界殑鎯呭喌鏃訛紝鐢眘cale鍙傛暟鎸?br /> * 瀹氱簿搴︼紝浠ュ悗鐨勬暟瀛楀洓鑸嶄簲鍏ャ?br /> * @param v1 琚櫎鏁?br /> * @param v2 闄ゆ暟
* @param scale 琛ㄧず琛ㄧず闇瑕佺簿紜埌灝忔暟鐐逛互鍚庡嚑浣嶃?br /> * @return 涓や釜鍙傛暟鐨勫晢
*/
public static double div(double v1,double v2,int scale){
if(scale<0){
throw new IllegalArgumentException(
"The scale must be a positive integer or zero");
}
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.divide(b2,scale,BigDecimal.ROUND_HALF_UP).doubleValue();
}
/**
* 鎻愪緵綺劇‘鐨勫皬鏁頒綅鍥涜垗浜斿叆澶勭悊銆?br /> * @param v 闇瑕佸洓鑸嶄簲鍏ョ殑鏁板瓧
* @param scale 灝忔暟鐐瑰悗淇濈暀鍑犱綅
* @return 鍥涜垗浜斿叆鍚庣殑緇撴灉
*/
public static double round(double v,int scale){
if(scale<0){
throw new IllegalArgumentException(
"The scale must be a positive integer or zero");
}
BigDecimal b = new BigDecimal(Double.toString(v));
BigDecimal one = new BigDecimal("1");
return b.divide(one,scale,BigDecimal.ROUND_HALF_UP).doubleValue();
}
};
]]>