如题:BigDecimal去掉小数点后无用的0
比如:数据库存储的是Decimal(5,2)类型保留两位数。
如果展示数据5.00,5.10等字样感觉很不爽,如何做呢?
只战术5和5.1
解决:BigDecimal,有方法解决stripTrailingZeros()
看源码:
/** * Returns a string representation of this {@code BigDecimal} * without an exponent field. For values with a positive scale, * the number of digits to the right of the decimal point is used * to indicate scale. For values with a zero or negative scale, * the resulting string is generated as if the value were * converted to a numerically equal value with zero scale and as * if all the trailing zeros of the zero scale value were present * in the result. * * The entire string is prefixed by a minus sign character "-" * (<tt>"\u002D"</tt>) if the unscaled value is less than * zero. No sign character is prefixed if the unscaled value is * zero or positive. * * Note that if the result of this method is passed to the * {@linkplain #BigDecimal(String) string constructor}, only the * numerical value of this {@code BigDecimal} will necessarily be * recovered; the representation of the new {@code BigDecimal} * may have a different scale. In particular, if this * {@code BigDecimal} has a negative scale, the string resulting * from this method will have a scale of zero when processed by * the string constructor. * * (This method behaves analogously to the {@code toString} * method in 1.4 and earlier releases.) * * @return a string representation of this {@code BigDecimal} * without an exponent field. * @since 1.5 * @see #toString() * @see #toEngineeringString() */ public String toPlainString() { if(scale==0) { if(intCompact!=INFLATED) { return Long.toString(intCompact); } else { return intVal.toString(); } } if(this.scale<0) { // No decimal point if(signum()==0) { return "0"; } int tailingZeros = checkScaleNonZero((-(long)scale)); StringBuilder buf; if(intCompact!=INFLATED) { buf = new StringBuilder(20+tailingZeros); buf.append(intCompact); } else { String str = intVal.toString(); buf = new StringBuilder(str.length()+tailingZeros); buf.append(str); } for (int i = 0; i < tailingZeros; i++) buf.append("0"); return buf.toString(); } String str ; if(intCompact!=INFLATED) { str = Long.toString(Math.abs(intCompact)); } else { str = intVal.abs().toString(); } return getValueString(signum(), str, scale); } /** * Returns a {@code BigDecimal} which is numerically equal to * this one but with any trailing zeros removed from the * representation. For example, stripping the trailing zeros from * the {@code BigDecimal} value {@code 600.0}, which has * [{@code BigInteger}, {@code scale}] components equals to * [6000, 1], yields {@code 6E2} with [{@code BigInteger}, * {@code scale}] components equals to [6, -2]. If * this BigDecimal is numerically equal to zero, then * {@code BigDecimal.ZERO} is returned. * * @return a numerically equal {@code BigDecimal} with any * trailing zeros removed. * @since 1.5 */ public BigDecimal stripTrailingZeros() { if (intCompact == 0 || (intVal != null && intVal.signum() == 0)) { return BigDecimal.ZERO; } else if (intCompact != INFLATED) { return createAndStripZerosToMatchScale(intCompact, scale, Long.MIN_VALUE); } else { return createAndStripZerosToMatchScale(intVal, scale, Long.MIN_VALUE); } }
demo
public class StringUtils { public static void main(String[] args) { System.out.println(BigDecimal.ZERO); System.out.println(new BigDecimal("2.0")); System.out.println(new Double("0")); System.out.println(new BigDecimal("2.00")); String d = new BigDecimal("100.10").stripTrailingZeros().toPlainString(); System.out.println(d); System.out.println(new BigDecimal("100.10").stripTrailingZeros().toPlainString()); } }
结果:
方法二:
private static final DecimalFormat decimalFormat = new DecimalFormat("###################.###########"); public static void main(String[] args) throws Exception{ System.out.print( "格式化结果:"); System.out.println(decimalFormat.format(new BigDecimal("10.10"))); }
结果:
Java BigDecimal 小数点处理
保留两位小数
方法一:
{ double c=3.154215; java.text.DecimalFormat myformat=new java.text.DecimalFormat("0.00"); String str = myformat.format(c); }
方式二:
{ java.text.DecimalFormat df =new java.text.DecimalFormat("#.00"); df.format(你要格式化的数字); 例:new java.text.DecimalFormat("#.00").format(3.1415926) #.00 表示两位小数 #.0000四位小数 以此类推... }
方式三:
{ double d = 3.1415926; String result = String .format("%.2f"); %.2f %. 表示 小数点前任意位数 2 表示两位小数 格式后的结果为f 表示浮点型 }
四舍五入
{ double f = 111231.5585; BigDecimal b = new BigDecimal(f); //保留2位小数 double f1 = b.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue(); }
public class PreciseCompute { //默认除法运算精度 private static final int DEF_DIV_SCALE = 10; /** * 提供精确的加法运算。 * @param v1 被加数 * @param v2 加数 * @return 两个参数的和 */ 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(); } /** * 提供精确的减法运算。 * @param v1 被减数 * @param v2 减数 * @return 两个参数的差 */ 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(); } /** * 提供精确的乘法运算。 * @param v1 被乘数 * @param v2 乘数 * @return 两个参数的积 */ 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(); } /** * 提供(相对)精确的除法运算,当发生除不尽的情况时,精确到 * 小数点以后10位,以后的数字四舍五入。 * @param v1 被除数 * @param v2 除数 * @return 两个参数的商 */ public static double div(double v1, double v2) { return div(v1, v2, DEF_DIV_SCALE); } /** * 提供(相对)精确的除法运算。当发生除不尽的情况时,由scale参数指 * 定精度,以后的数字四舍五入。 * @param v1 被除数 * @param v2 除数 * @param scale 表示表示需要精确到小数点以后几位。 * @return 两个参数的商 */ 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(); } /** * 提供精确的小数位四舍五入处理。 * @param v 需要四舍五入的数字 * @param scale 小数点后保留几位 * @return 四舍五入后的结果 */ 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 ne = new BigDecimal("1"); return b.divide(one, scale, BigDecimal.ROUND_HALF_UP).doubleValue(); } }
my code:
private BigDecimal formatComma2BigDecimal(Object obj) { String val = String.valueOf(obj); if (val == null) return new BigDecimal("0.00"); val = val.replaceAll(",", ""); if (!isNumber(val)) return new BigDecimal("0.00"); BigDecimal decimal = new BigDecimal(val); decimal = decimal.setScale(2, RoundingMode.HALF_UP); return decimal; } private String formatCommaAnd2Point(Object obj) { BigDecimal decimal = formatComma2BigDecimal(obj); DecimalFormat df = new DecimalFormat("#,###.00"); String decimalStr = df.format(decimal).equals(".00")?"0.00":df.format(decimal); if(decimalStr.startsWith(".")){ decimalStr = "0"+decimalStr; } return decimalStr; } private boolean isDouble(String value) { try { Double.parseDouble(value); if (value.contains(".")) return true; return false; } catch (NumberFormatException e) { return false; } } private boolean isInteger(String value) { try { Integer.parseInt(value); return true; } catch (NumberFormatException e) { return false; } } private boolean isNumber(String value) { return isInteger(value) || isDouble(value); }
详细还是参看JavaSE 帮助文档吧~以上为个人经验,希望能给大家一个参考,也希望大家多多支持服务器之家。
原文链接:https://blog.csdn.net/qq_31564573/article/details/105534900