Java大数类【转】

原博：https://www.cnblogs.com/Leonard-/p/7636639.html

 

大数相加：

//JAVA 大数相加 
import java.math.BigInteger;
import java.util.*;
import java.io.*;

public class Main
{
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);
            BigInteger a = cin.nextBigInteger();
            BigInteger b = cin.nextBigInteger();
            BigInteger ans = a.add(b);
            System.out.println(ans);
    }
}

 

大数相乘：

//JAVA 大数相乘 
import java.math.BigInteger;
import java.util.*;
import java.io.*;

public class Main
{
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);
            BigInteger a = cin.nextBigInteger();
            BigInteger b = cin.nextBigInteger();
            BigInteger ans = a.multiply(b);
            System.out.println(ans);
    }
}

 

大数相减：public BigInteger subtract(BigInteger val)

大数相除：public BigInteger divide(BigInteger val)

 

大数阶乘：

//JAVA 大数阶乘 
import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class Main
{
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);    
        int n = cin.nextInt(); //输入int型 
        BigInteger ans = BigInteger.ONE;
        for(int i = 1; i <= n; i++)
        ans = ans.multiply(BigInteger.valueOf(i));
        System.out.println(ans);
    }
}

 

大数比较大小

//JAVA 大数比较大小 
import java.io.*;
import java.math.BigInteger;
import java.util.*;

public class Main
{
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);    
        while(cin.hasNext())
        {
            BigInteger a = cin.nextBigInteger();
            BigInteger b = cin.nextBigInteger();
            if(a.equals(BigInteger.ZERO) && b.equals(BigInteger.ZERO)) break;
            int flag = a.compareTo(b);
            if(flag == -1)
                System.out.println("ab");
        }
    }
}

 

高精度幂

//JAVA 高精度幂 
import java.io.*;
import java.math.BigDecimal;
import java.util.*;

public class Main
{
    public static void main(String args[])
    {
        Scanner cin = new Scanner(System.in);    
        while(cin.hasNext())
        {
            BigDecimal ans = cin.nextBigDecimal();
            int n = cin.nextInt();
            String res = ans.pow(n).stripTrailingZeros().toPlainString(); //整数去掉后面的0和小数点 
            if(res.startsWith("0")) //去掉前导0 
            {
                res = res.substring(1);
            }
            System.out.println(res);
        }
    }
}

//这里的BigDecimal相当于double，但是精度更高