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);
构造器 描述 BigDecimal(int) 创建一个具有参数所指定整数值的对象。 BigDecimal(double) 创建一个具有参数所指定双精度值的对象。 BigDecimal(long) 创建一个具有参数所指定长整数值的对象。 BigDecimal(String) 创建一个具有参数所指定以字符串表示的数值的对象。
方法 描述 add(BigDecimal) BigDecimal对象中的值相加，然后返回这个对象。 subtract(BigDecimal) BigDecimal对象中的值相减，然后返回这个对象。 multiply(BigDecimal) BigDecimal对象中的值相乘，然后返回这个对象。 divide(BigDecimal) BigDecimal对象中的值相除，然后返回这个对象。 toString() 将BigDecimal对象的数值转换成字符串。 doubleValue() 将BigDecimal对象中的值以双精度数返回。 floatValue() 将BigDecimal对象中的值以单精度数返回。 longValue() 将BigDecimal对象中的值以长整数返回。 intValue() 将BigDecimal对象中的值以整数返回。
BigDecimal a = new BigDecimal(1.01);
BigDecimal b = new BigDecimal(1.02);
BigDecimal c = new BigDecimal("1.01");
BigDecimal d = new BigDecimal("1.02");
System.out.println(a.add(b));
System.out.println(c.add(d));
* The results of this constructor can be somewhat unpredictable.
* One might assume that writing {@codenew BigDecimal(0.1)} in
* Java creates a {@code BigDecimal} which is exactly equal to
* 0.1 (an unscaled value of 1, with a scale of 1), but it is
* actually equal to
* 0.1000000000000000055511151231257827021181583404541015625.
* This is because 0.1 cannot be represented exactly as a
* {@codedouble} (or, for that matter, as a binary fraction of
* any finite length). Thus, the value that is being passed
* <i>in</i> to the constructor is not exactly equal to 0.1,
* appearances notwithstanding.
……
* When a {@codedouble} must be used as a source for a
* {@code BigDecimal}, note that this constructor provides an
* exact conversion; it does not give the same result as
* converting the {@codedouble} to a {@code String} using the
* {@link Double#toString(double)} method and then using the
* {@link #BigDecimal(String)} constructor. To get that result,
* use the {@codestatic} {@link #valueOf(double)} method.
* </ol>
public BigDecimal(double val) {
this(val,MathContext.UNLIMITED);
}
/**
* @author: Ji YongGuang.
* @date: 19:50 2017/12/14.
*/
publicclass BigDecimalUtil {
private BigDecimalUtil() {
}
public static BigDecimal add(double v1, double v2) {// v1 v2
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.add(b2);
}
public static BigDecimal sub(double v1, double v2) {
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.subtract(b2);
}
public static BigDecimal mul(double v1, double v2) {
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
return b1.multiply(b2);
}
public static BigDecimal div(double v1, double v2) {
BigDecimal b1 = new BigDecimal(Double.toString(v1));
BigDecimal b2 = new BigDecimal(Double.toString(v2));
// 2 = 保留小数点后两位 ROUND_HALF_UP = 四舍五入
return b1.divide(b2, 2, BigDecimal.ROUND_HALF_UP);// 应对除不尽的情况
}
}