BigInteger multiply() Method in Java with Examples - GeeksforGeeks

12 Apr, 2019
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 of12345678901234567654632498739473and12345678901234561247612748612746is152415787532388282591353462245536419067346861445890674421122858
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 of123456789012345678901234567890123456789012345678901234567890123456789012345678901654632498739473and123456789012345678901234567890123456789012345678901234567890123456789012345678961247612748612746is15241578753238836750495351562566681945008382873376009755225118122311263526910008985036532509972574264073578551235889967606442208008929541925721486305055001841778994861500543809890674421122858
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)
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