function2()
> 將數字四捨五入至某小數位, 並返回指定位數字串
> function2(123.455,2) => 123.46
> function2(123.449,2) => 123.45
> function2(123.44,3) => 123.440
> function2(123.4455,3) => 123.446
> function2(123.4499,3) => 123.450
> function2(123.9,0) => 124
> 程式接口:
> public static double function2(double value,int decimalPlaces);
>
> 將數字四捨五入至某小數位, 並返回指定位數字串
> function2(123.455,2) => 123.46
> function2(123.449,2) => 123.45
> function2(123.44,3) => 123.440
> function2(123.4455,3) => 123.446
> function2(123.4499,3) => 123.450
> function2(123.9,0) => 124
> 程式接口:
> public static double function2(double value,int decimalPlaces);
>
package com.nec.fastunit.common;import java.math.BigDecimal;
public class FormatNumber { public static String formatNumber(String number,int weishu){
// 判断字符串是否为空
if(number == null || (number.trim().length() == 0)){
// System.out.println("输入的数字为空,请输入数字");
return "";
}
// 判断字符串里有除点号之外的非数字存在
char[] strArray = number.toCharArray(); for(int i = 0; i < strArray.length; i++){
if((strArray[i] < '0' || strArray[i] > '9')&& (strArray[i] != '.' && strArray[i] != '-' && strArray[i] != 'E')){
// System.out.println("您输入的字符串中含有非法字符,请重新输入");
return number;
}else if(strArray[i] == 'E'){
if(strArray[0] == '-'){
number = number.substring(1,number.length());
String numstr = orinum(number);
numstr = "-" + numstr;
number = numstr;
}else{
number = orinum(number);
}
}
}
// 四舍五入后得数
number = String.valueOf(numz(Double.valueOf(number),weishu));
// 判断小数位数为0的情况
if(number.indexOf(".") != -1 && weishu == 0){
int pointNumber = number.indexOf(".");
String strFirst = number.substring(0,pointNumber);
// 小数点前字符串分割
strFirst = splitFirstNumber(strFirst);
return strFirst;
}
// 判断没有小数点,但小数位数要求有位数的情况
if(number.indexOf(".") == -1 && weishu != 0){
number = number + ".";
for(int i = 0; i < weishu; i++){
number = number + "0";
}
int pointNumber = number.indexOf(".");
String strFirst = number.substring(0,pointNumber);
String strLast = number.substring(pointNumber + 1,number.length());
// 小数点前字符串分割
strFirst = splitFirstNumber(strFirst);
// 小数点后字符串分割
strLast = splitLastNumber(strLast);
return strFirst + "." + strLast;
}
// 判断没有小数部分的情况
if((number.indexOf(".") == -1) && weishu == 0){
// 小数点前字符串分割
number = splitFirstNumber(number);
return number;
} else {
int pointNumber = number.indexOf(".");
String strFirst = number.substring(0,pointNumber);
String strLast = number.substring(pointNumber + 1,number.length());
// 小数位数判断
strLast = formatPoint(strLast,weishu);
// 小数点前字符串分割
strFirst = splitFirstNumber(strFirst);
// 小数点后字符串分割
strLast = splitLastNumber(strLast);
return strFirst + "." + strLast;
}
}
/**
*
* @param str 小数点前的字符串
* @return 返回小数点前的逗号分割
*/
public static String splitFirstNumber(String str){
char[] strArray = str.toCharArray();
if(strArray[0] == '-'){
StringBuffer strBuffer = new StringBuffer();
strBuffer.append(str);
strBuffer.reverse();
str = strBuffer.toString();
StringBuffer sb = new StringBuffer();
for(int i = 0; i < str.length(); i=i+3){
if(i+3 < str.length()){
String str1 = str.substring(i,i+3);
sb.append(str1);
if(i+3 == str.length() -1){
//
}else{
sb.append(",");
}
} else {
String str2 = str.substring(i,str.length());
sb.append(str2);
}
}
sb.reverse();
return sb.toString(); }else{
StringBuffer strBuffer = new StringBuffer();
strBuffer.append(str);
strBuffer.reverse();
str = strBuffer.toString();
StringBuffer sb = new StringBuffer();
for(int i = 0; i < str.length(); i=i+3){
if(i+3 < str.length()){
String str1 = str.substring(i,i+3);
sb.append(str1);
sb.append(",");
} else {
String str2 = str.substring(i,str.length());
sb.append(str2);
}
}
sb.reverse();
return sb.toString();
}
}
/**
*
* @param str 小数点后字符串
* @return 逗号分割后的字符串
*/
public static String splitLastNumber(String str){
StringBuffer sb = new StringBuffer();
for(int i = 0; i < str.length(); i=i+3){
if(i+3 < str.length()){
String str1 = str.substring(i,i+3);
sb.append(str1);
sb.append(",");
} else {
String str2 = str.substring(i,str.length());
sb.append(str2);
}
}
return sb.toString();
}
/**
*
* @param laststr 小数点后字符串
* @param bitWei 截取的字符串长度
* @return 返回小数点后应得的字符串
*/
public static String formatPoint(String laststr,int bitWei){
int n = laststr.length();
if(n < bitWei){
for(int i = 0; i < bitWei - n; i++){
laststr = laststr + "0";
}
} else {
BigDecimal bd = new BigDecimal("0." + laststr).setScale(bitWei,BigDecimal.ROUND_HALF_UP);
laststr = bd.toString();
laststr = laststr.substring(2,laststr.length());
}
return laststr;
}
// 处理科学计数法
public static String orinum(String str){
int index = str.indexOf("E");
String lstr = str.substring(index + 1, str.length());
int pindex = str.indexOf(".");
// System.out.println("pindex: " + pindex);
// 取小数点后到E之间的字符串
String midstr = str.substring(pindex + 1,index);
// 取小数点前字符
String pstr = str.substring(0,pindex);
// 判断E后数字是正还是负
Integer e = Integer.parseInt(lstr);
String nstr = null;
if(e > 0){
if(midstr.length() > e){
nstr = pstr + midstr.substring(0,e) + "." + midstr.subSequence(e, midstr.length());
}else{
nstr = pstr + midstr;
for(int i = 0; i < e - midstr.length(); i++){
nstr = nstr + "0";
}
}
}else{
if(pstr.length() > -e){
nstr = pstr.substring(0,pindex + e) + "." + pstr.substring(pindex+e,pstr.length()) + midstr;
}else{
nstr = pstr + midstr;
for(int i = 0; i < -e - pstr.length(); i++){
nstr = "0" + nstr;
}
nstr = "0." + nstr;
}
}
return nstr;
}
public static double numz(double numstr,int bitshu){
BigDecimal b = new BigDecimal(Double.toString(numstr));
String finalnum = b.setScale(bitshu, BigDecimal.ROUND_HALF_EVEN).toString();
return Double.valueOf(finalnum);
}
}
把formatNumber(String number,int weishu)改为你的接口方式即可
double a=(int)(value*10^decimalPlace+0.5)/100.0;
return a;
}应该没问题,很简单的一个小程序
public static double function2(double value,int decimalPlaces){
double deciValue = Math.pow(10, decimalPlaces);
return Math.ceil(value * deciValue) / deciValue;
}
public static void main(String args[]){
double value=123.9999;
String replacestr=new Double(value).toString();
FormatNumber formatnumber=new FormatNumber();
String str=formatnumber.formatNumber(replacestr, 3);
System.out.println(str);
}
试试这两个方法,都可以:
double one(double d, int i)
{
double a = Math.pow(10, i);
return Math.floor(d * a + 0.5) / a;
} double two(double d, int i)
{
double a = Math.pow(10, i);
return Math.ceil(d * a - 0.5) / a;
}
一楼的好长,等会儿看。
二楼的用错了运算符,^ 是异或运算符
四楼的结果也不对。希望我这个是对的。 o(∩_∩)o
double deciValue = Math.pow(10, decimalPlaces);
return Math.round(value * deciValue) / deciValue;
}
很有帮助!!!!
=======================================================
System.out.println("one:" + one(123.4455,3));
System.out.println("two:" + two(123.4455,3));
System.out.println("function2:" + function2(123.4455,3));
System.out.println("\none:" + one(123.4499,3));
System.out.println("two:" + two(123.4499,3));
System.out.println("function2:" + function2(123.4499,3));
System.out.println("\none:" + one(123.455,2));
System.out.println("two:" + two(123.455,2));
System.out.println("function2:" + function2(123.455,2));==========》
one:123.446
two:123.445
function2:123.446one:123.45
two:123.45
function2:123.45one:123.46
two:123.45
function2:123.46是不是要这样的结果?
哪个不正确?
不知道你这个+ - 0.5是什么意思?
+0.5然后采用floor这不是玩弄floor吗?