这个千篇一律,Double是对基本数据类型double的包装,里面包含了double类型的字段。这个类也提供了一些将String和double转换为Double的方法,还有一些处理double的方法。
作者是:
* @author Lee Boynton* @author Arthur van Hoff* @author Joseph D. Darcy* @since JDK1.0
提供了很多属性值,如下:
java double转float、正无穷:POSITIVE_INFINITY:Double.longBitsToDouble(0x7ff0000000000000L)
负无穷:NEGATIVE_INFINITY:Double.longBitsToDouble(0xfff0000000000000L)
非数字:Not-a-Number (NaN):Double.longBitsToDouble(0x7ff8000000000000L)
最大值:MAX_VALUE:Double.longBitsToDouble(0x7fefffffffffffffL)
单精度最小值:MIN_NORMAL:Double.longBitsToDouble(0x0010000000000000L)
javastring转double。双精度最小值:MIN_VALUE:Double.longBitsToDouble(0x1L)
最大指数:MAX_EXPONENT:1023
最小指数:MIN_EXPONENT:-1022
toString:很简单
toHexString:将double转换为16进制字符串,就是StringBuilder的字符串拼接:
public static String toHexString(double d) {if (!isFinite(d) )//如果是NaN或是无穷,直接返回对应的字符串形式return Double.toString(d);else {//初始化最大长度:24StringBuilder answer = new StringBuilder(24);if (Math.copySign(1.0, d) == -1.0) // value is negative,answer.append("-"); // so append sign infoanswer.append("0x");d = Math.abs(d);if(d == 0.0) {answer.append("0.0p0");} else {boolean subnormal = (d < DoubleConsts.MIN_NORMAL);// Isolate significand bits and OR in a high-order bit// so that the string representation has a known// length.long signifBits = (Double.doubleToLongBits(d)& DoubleConsts.SIGNIF_BIT_MASK) |0x1000000000000000L;// Subnormal values have a 0 implicit bit; normal// values have a 1 implicit bit.answer.append(subnormal ? "0." : "1.");// Isolate the low-order 13 digits of the hex// representation. If all the digits are zero,// replace with a single 0; otherwise, remove all// trailing zeros.String signif = Long.toHexString(signifBits).substring(3,16);answer.append(signif.equals("0000000000000") ? // 13 zeros"0":signif.replaceFirst("0{1,12}$", ""));answer.append('p');// If the value is subnormal, use the E_min exponent// value for double; otherwise, extract and report d's// exponent (the representation of a subnormal uses// E_min -1).answer.append(subnormal ?DoubleConsts.MIN_EXPONENT:Math.getExponent(d));}return answer.toString();}}
java double 转float?判断是否为NaN
public static boolean isNaN(double v) {return (v != v);}
判断是否无限
public static boolean isInfinite(double v) {return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);}
判断是否有限
public static boolean isFinite(double d) {return Math.abs(d) <= DoubleConsts.MAX_VALUE;}
haseCode被重写了
public static int hashCode(double value) {long bits = doubleToLongBits(value);return (int)(bits ^ (bits >>> 32));}
doubleToLongBits:很多方法中用到了这个方法,理解为将double转换为64位的long即可
0x8000000000000000L
选择的位)表示浮点数的符号。 位62-52(由掩码0x7ff0000000000000L
选择的位)表示指数。 位51-0(由掩码0x000fffffffffffffL
选择的位)表示浮点数的有效数(有时称为尾数)。0x7ff0000000000000L
。0xfff0000000000000L
。0x7ff8000000000000L
。long
整数,当给予longBitsToDouble(long)
方法时,将产生与doubleToLongBits
的参数相同的浮点值(除了所有NaN值都被折叠为单个“规范”NaN值)。 public static long doubleToLongBits(double value) {long result = doubleToRawLongBits(value);// Check for NaN based on values of bit fields, maximum// exponent and nonzero significand.if ( ((result & DoubleConsts.EXP_BIT_MASK) ==DoubleConsts.EXP_BIT_MASK) &&(result & DoubleConsts.SIGNIF_BIT_MASK) != 0L)result = 0x7ff8000000000000L;return result;}
float在java中怎么用,doubleToRawLongBits:与doubleToLongBits
方法不同, doubleToRawLongBits
不会将编码NaN的所有位模式折叠到单个“规范”NaN值。是一个native的方法了。
public static native long doubleToRawLongBits(double value);
compare:重写比较,注意Double.NaN返回是0
public static int compare(double d1, double d2) {if (d1 < d2)return -1; // Neither val is NaN, thisVal is smallerif (d1 > d2)return 1; // Neither val is NaN, thisVal is larger// Cannot use doubleToRawLongBits because of possibility of NaNs.long thisBits = Double.doubleToLongBits(d1);long anotherBits = Double.doubleToLongBits(d2);return (thisBits == anotherBits ? 0 : // Values are equal(thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)1)); // (0.0, -0.0) or (NaN, !NaN)}
还有三个运算方法
sum,max,min
Float与Double非常类似,不再单独讲解
版权声明:本站所有资料均为网友推荐收集整理而来,仅供学习和研究交流使用。
工作时间:8:00-18:00
客服电话
电子邮件
admin@qq.com
扫码二维码
获取最新动态