保留小数点位数和格式

JS 中

1. double运算
c = parseFloat(a) + parseFloat(b))

2. 四舍五入，保留两位小数
c = c.toFixed(2);

3. 去掉小数点后面多余的0
c = c.toFixed(2)*100/100;


JAVA中

//四舍五入，保留指定小数位
public static Double roundDouble(Object obj, int scale){

double d = 0;
try{
d = Double.parseDouble(obj.toString().replaceAll(",", ""));
} catch (Exception e) {
d = 0;
}

//四舍五入，保留两位小数
BigDecimal bd = new BigDecimal(d);
bd = bd.setScale(scale, BigDecimal.ROUND_HALF_UP);
d = bd.doubleValue();

return d;
}


//转成字符串，去掉科学计数法
public static String roundFormat(Object obj){
String str = "0";
try{
Double d = Double.parseDouble(obj.toString().replaceAll(",", ""));

//四舍五入，保留两位小数
BigDecimal bd = new BigDecimal(d);
bd = bd.setScale(2, BigDecimal.ROUND_HALF_UP);
d = bd.doubleValue();

//去除科学计数法
DecimalFormat df = new DecimalFormat("#.##");
str = df.format(d);

} catch (Exception e) {
str = "0";
}


return str;
}


//除法
public static Double divideRound(Double a, Double b){
try {
if (b == 0) {
return 0.0;
} else {
BigDecimal bd = new BigDecimal(a/b);
bd = bd.setScale(2, BigDecimal.ROUND_HALF_UP);
double d = bd.doubleValue();
bd = null;
return d;
}
} catch (Exception e) {
return 0.0;
}
}

//四舍五入，保留指定小数位
public static Double roundDouble(Object obj, int scale){double d = 0;try{d  = Double.parseDouble(obj.toString().replaceAll(",", ""));} catch (Exception e) {d = 0;}//四舍五入，保留两位小数BigDecimal bd = new BigDecimal(d);  bd = bd.setScale(scale, BigDecimal.ROUND_HALF_UP);d = bd.doubleValue(); return d;}//转成字符串，去掉科学计数法
public static String roundFormat(Object obj){String str = "0";try{Double d  = Double.parseDouble(obj.toString().replaceAll(",", ""));//四舍五入，保留两位小数BigDecimal bd = new BigDecimal(d);  bd = bd.setScale(2, BigDecimal.ROUND_HALF_UP);d = bd.doubleValue(); //去除科学计数法 DecimalFormat df = new DecimalFormat("#.##"); str = df.format(d);			} catch (Exception e) {str = "0";}return str;}//除法
public static Double divideRound(Double a, Double b){try {if (b == 0) {return 0.0;} else {BigDecimal bd = new BigDecimal(a/b);  bd = bd.setScale(2, BigDecimal.ROUND_HALF_UP);  double d = bd.doubleValue();  bd = null;  return d;  }} catch (Exception e) {return 0.0;}}