java 4舍5入_java四舍五入问题

//#1

public double round(double in) {

double dec = in – (int)in;

double out = dec >= 0.5 ?

(int)i + ((int)((dec – 0.5) / 0.25)) * 0.5 + 0.5 :

(int)i + ((int)(dec / 0.25)) * 0.5;

return out;

}

//Math.round()。(仅适用于对十分位做四舍五入)

public double round(double in) {

double in2 = Math.round(2 * in);

return d / 2;

}

//#3.BigDecimal的实例方法setScale(int newScale, int roundingMode)

public double round(double in) {

BigDecimal in2 = BigDecimal.valueOf(2 * in);

//0:保留0位小数

//BigDecimal.ROUND_HALF_UP：五入

return dec.setScale(0, BigDecimal.ROUND_HALF_UP).doubleValue() / 2;

}