Java BigInteger multiply()方法及示例

java.math.BigInteger .multiply(BigInteger val) 用于计算两个BigIntegers的乘法。由于BigInteger类内部使用整数数组进行处理，因此对BigInteger对象的操作不如对基数的操作快。

语法

public BigInteger multiply(BigInteger val)

参数： 该方法接受一个参数val，即要与这个BigInteger相乘的值。

返回值： 该方法返回一个BigInteger，该BigInteger持有乘法（this * val）。

下面的程序用来说明BigInteger的multiply()方法。

例1:

// Java program to demonstrate
// multiply() method of BigInteger
  
import java.math.BigInteger;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // BigInteger object to store result
        BigInteger mult;
  
        // For user input
        // Use Scanner or BufferedReader
  
        // Two objects of String created
        // Holds the values to calculate the multiplication
        String input1 = "012345678901234567"
                        + "654632498739473";
  
        String input2 = "0123456789012345"
                        + "61247612748612746";
  
        // Convert the string input to BigInteger
        BigInteger a
            = new BigInteger(input1);
        BigInteger b
            = new BigInteger(input2);
  
        // Using multiply() method
        mult = a.multiply(b);
  
        // Display the result in BigInteger
        System.out.println("The multiplication of\n"
                           + a + " \nand\n" + b + " "
                           + "\nis\n" + mult);
    }
}

输出。

The multiplication of
12345678901234567654632498739473
and
12345678901234561247612748612746
is
152415787532388282591353462245536419067346861445890674421122858

例2:

// Java program to demonstrate
// multiply() method of BigInteger
  
import java.math.BigInteger;
  
public class GFG {
    public static void main(String[] args)
    {
        // BigInteger object to store result
        BigInteger mult;
  
        // For user input
        // Use Scanner or BufferedReader
  
        // Two objects of String created
        // Holds the values to calculate the multiplication
        String input1 = "012345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "654632498739473";
  
        String input2 = "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "61247612748612746";
  
        // Convert the string input to BigInteger
        BigInteger a
            = new BigInteger(input1);
        BigInteger b
            = new BigInteger(input2);
  
        // Using multiply() method
        mult = a.multiply(b);
  
        // Display the result in BigInteger
        System.out.println("The multiplication of\n"
                           + a + " \nand\n" + b + " "
                           + "\nis\n" + mult + "\n");
  
        // Using double to hold  the result
        double d = Double.parseDouble(mult.toString());
  
        // Display the result in double
        System.out.println("Using double, multiplication is "
                           + d);
    }
}

输出。

The multiplication of
123456789012345678901234567890123456789012345678901234567890123456789012345678901654632498739473
and
123456789012345678901234567890123456789012345678901234567890123456789012345678961247612748612746
is
15241578753238836750495351562566681945008382873376009755225118122311263526910008985036532509972574264073578551235889967606442208008929541925721486305055001841778994861500543809890674421122858

Using double, multiplication is 1.5241578753238838E190

从上面的例子可以看出，使用BigInteger时，数据是完全精确的。

参考: https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/math/BigInteger.html#multiply(java.math.BigInteger)