Java5：BigInteger、BigDecimal详解

package lavasoft;

import java.math.BigInteger;
import java.util.Random;

/**
* 测试BigInteger
*
* @author leizhimin 2009-11-17 12:49:41
*/

public class TestBigInteger {
public static void main(String[] args) {
System.out.println("-------------------构造BigInteger---------------------");
//通过byte数组来创建BigInteger
BigInteger bi1 = new BigInteger(new byte[]{1, 1});
System.out.println("bi1=" + bi1.toString());
//创建带符号的BigInteger
BigInteger bi2 = new BigInteger(-1, new byte[]{1, 1});
System.out.println("bi2=" + bi2.toString());
//创建带符号的BigInteger随机数
BigInteger bi3 = new BigInteger(128, 20, new Random());
System.out.println("bi3=" + bi3.toString());
//通过10进制字符串创建带符号的BigInteger
BigInteger bi4 = new BigInteger("12342342342342123423423412341");
System.out.println("bi4=" + bi4.toString());
//通过10进制字符串创建带符号的BigInteger
BigInteger bi5 = new BigInteger("88888888888888888888888888888", Character.digit('a', 33));
System.out.println("bi5=" + bi5.toString());
System.out.println("BigInteger的常量：");
System.out.println("BigInteger.ZERO=" + BigInteger.ZERO);
System.out.println("BigInteger.ONE=" + BigInteger.ONE);
System.out.println("BigInteger.TEN=" + BigInteger.TEN);

System.out.println("-------------------使用BigInteger---------------------");
System.out.println("bi1的相反数=" + bi1.negate());
System.out.println("bi1的相反数=" + bi1.negate());
System.out.println("bi1+bi2=" + bi1.add(bi2));
System.out.println("bi1-bi2=" + bi1.subtract(bi2));
System.out.println("bi1*bi2=" + bi1.multiply(bi2));
System.out.println("bi1/bi2=" + bi1.divide(bi2));
System.out.println("bi1的10次方=" + bi1.pow(10));
System.out.println("bi1的10次方=" + bi1.pow(1));
BigInteger[] bx = bi4.divideAndRemainder(bi1);
System.out.println(">>>:bx[0]=" + bx[0] + ",bx[1]=" + bx[1]);
System.out.println("bi2的绝对值=" + bi2.abs());
}
}

-------------------构造BigInteger---------------------
bi1=257
bi2=-257
bi3=175952079487573456985958549621373190227
bi4=12342342342342123423423412341
bi5=88888888888888888888888888888
BigInteger的常量：
BigInteger.ZERO=0
BigInteger.ONE=1
BigInteger.TEN=10
-------------------使用BigInteger---------------------
bi1的相反数=-257
bi1的相反数=-257
bi1+bi2=0
bi1-bi2=514
bi1*bi2=-66049
bi1/bi2=-1
bi1的10次方=1256988294225653106805249
bi1的10次方=257
>>>:bx[0]=48024678374872075577523005,bx[1]=56
bi2的绝对值=257

Process finished with exit code 0

java.math.MathContext：

java.math.RoundingMode：这是一种枚举类型，定义了很多常用的数据舍入方式。

package lavasoft;

import java.math.BigDecimal;
import java.math.MathContext;
import java.math.RoundingMode;

/**
* 测试BigDecimal
*
* @author leizhimin 2009-11-17 12:50:03
*/

public class TestBigDecimal {

public static void main(String[] args) {
System.out.println("------------构造BigDecimal-------------");
//从char[]数组来创建BigDecimal
BigDecimal bd1 = new BigDecimal("123456789.123456888".toCharArray(), 4, 12);
System.out.println("bd1=" + bd1);
//从char[]数组来创建BigDecimal
BigDecimal bd2 = new BigDecimal("123456789.123456111133333213".toCharArray(), 4, 18, MathContext.DECIMAL128);
System.out.println("bd2=" + bd2);
//从字符串创建BigDecimal
BigDecimal bd3 = new BigDecimal("123456789.123456111133333213");
System.out.println("bd3=" + bd3);
//从字符串创建BigDecimal，3是有效数字个数
BigDecimal bd4 = new BigDecimal("88.456", new MathContext(3, RoundingMode.UP));
System.out.println("bd4=" + bd4);
System.out.println("------------使用BigDecimal-------------");
System.out.println("bd1+bd2=" + bd1.add(bd2));
System.out.println("bd1+bd2=" + bd1.add(bd2, new MathContext(24, RoundingMode.UP)));
System.out.println("bd1-bd2=" + bd1.subtract(bd2).toPlainString());
System.out.println("bd1-bd2=" + bd1.subtract(bd2, new MathContext(24, RoundingMode.UP)).toPlainString());
System.out.println("bd1*bd2=" + bd1.multiply(bd2));
System.out.println("bd1*bd2=" + bd1.multiply(bd2, new MathContext(24, RoundingMode.UP)));
System.out.println("bd1/bd4=" + bd1.divideToIntegralValue(bd4));
System.out.println("bd1/bd4=" + bd1.divideToIntegralValue(bd4, new MathContext(24, RoundingMode.UP)));
System.out.println("bd1末位数据精度=" + bd1.ulp());
System.out.println("bd2末位数据精度=" + bd2.ulp());
System.out.println("bd2末位数据精度=" + bd2.ulp().toPlainString());
System.out.println("bd1符号：" + bd1.signum());
System.out.println("bd4的标度：" + bd4.scale());
}
}

------------构造BigDecimal-------------
bd1=56789.123456
bd2=56789.123456111133
bd3=123456789.123456111133333213
bd4=88.5
------------使用BigDecimal-------------
bd1+bd2=113578.246912111133
bd1+bd2=113578.246912111133
bd1-bd2=-0.000000111133
bd1-bd2=-0.000000111133
bd1*bd2=3225004542.907120529593035648
bd1*bd2=3225004542.90712052959304
bd1/bd4=641.00000
bd1/bd4=641.00000
bd1末位数据精度=0.000001
bd2末位数据精度=1E-12
bd2末位数据精度=0.000000000001
bd1符号：1
bd4的标度：1

Process finished with exit code 0

java.math包：