BigInteger multiply() Method in Java with Examples

The java.math.BigInteger.multiply(BigInteger val) is used to calculate the multiplication of two BigIntegers. As BigInteger class internally uses an array of integers for processing, the operation on an object of BigInteger are not as fast as on primitives.

Syntax:

public BigInteger multiply(BigInteger val)

Parameters: This method accepts a parameter val which is the value to be multiplied to this BigInteger.

Return value: This method returns a BigInteger which holds multiplication (this * val).

Below programs is used to illustrate the multiply() method of BigInteger.

Example 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);
    }
}

Output:

The multiplication of
12345678901234567654632498739473
and
12345678901234561247612748612746
is
152415787532388282591353462245536419067346861445890674421122858

Example 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);
    }
}

Output:

The multiplication of
123456789012345678901234567890123456789012345678901234567890123456789012345678901654632498739473
and
123456789012345678901234567890123456789012345678901234567890123456789012345678961247612748612746
is
15241578753238836750495351562566681945008382873376009755225118122311263526910008985036532509972574264073578551235889967606442208008929541925721486305055001841778994861500543809890674421122858

Using double, multiplication is 1.5241578753238838E190

As from the above examples, it is clear that the data is full precise when BigInteger is used.

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