Java 8 | BigInteger longValueExact() Method with Examples

java.math.BigInteger.longValueExact() was introduced in Java 8. It is an inbuilt function which converts the value of BigInteger to a long and checks for lost information. If the value of BigInteger is greater than 9,223,372,036,854,775,807 or less than -9,223,372,036,854,775,808; the method will throw ArithmeticException as BigInteger doesn’t fit in long range.

Syntax:

public long longValueExact()

Return Value: This method returns the long value of this BigInteger.

Exception: The method throws ArithmeticException if the value of BigInteger is greater than 9,223,372,036,854,775,807 or less than -9,223,372,036,854,775,808; as this range doesn’t fit in long range.

Example:

Input: 98169894145
Output: 98169894145
Explanation: 98169894145 is given as input which is BigInteger
and long value of 98169894145 is 98169894145

Input: -65416518651
Output: -65416518651
Explanation: -65416518651 is given as input which is BigInteger 
and long value of -65416518651 is -65416518651

Input: 10000000000000000000
Output: ArithmeticException
Explanation: When 10000000000000000000 is tried to convert to long,
since 10000000000000000000 > 9,223,372,036,854,775,807 (greater than a long's range), 
therefore it throws an arithmetic exception.

Below programs illustrates longValueExact() method of BigInteger class:

Program 1: To demonstrate longValueExact() method for positive number <9,223,372,036,854,775,807

// Java program to demonstrate longValueExact()
// method of BigInteger Class

import java.math.*;

public class GFG {

    public static void main(String[] args)
    {
        // Creating a BigInteger object
        BigInteger big;
        big = new BigInteger("98169894145");

        // print value of BigInteger
        System.out.println("BigInteger value : "
                           + big);

        // convert big to the long value
        long b1 = big.longValueExact();

        // print long value
        System.out.println("long converted value : "
                           + b1);
    }
}

Output:

BigInteger value : 98169894145
long converted value : 98169894145

Program 2: To demonstrate longValueExact() method for negative number >-9,223,372,036,854,775,808

// Java program to demonstrate longValueExact()
// method of BigInteger Class

import java.math.*;

public class GFG {

    public static void main(String[] args)
    {

        // Creating a BigInteger object
        BigInteger big = new BigInteger("-65416518651");

        // print value of BigInteger
        System.out.println("BigInteger value : "
                           + big);

        // convert big to the long value
        long b1 = big.longValueExact();

        // print long value
        System.out.println("long converted value : "
                           + b1);
    }
}

Output:

BigInteger value : -65416518651
long converted value : -65416518651

Program 3: To demonstrate longValueExact() method for negative number <-9,223,372,036,854,775,808. It will throw Arithmetic Exception

// Java program to demonstrate longValueExact()
// method of BigInteger Class

import java.math.*;

public class GFG {

    public static void main(String[] args)
    {

        // Creating a BigInteger object
        BigInteger big = new BigInteger("-10000000000000000000");

        // print value of BigInteger
        System.out.println("BigInteger value : "
                           + big);

        try {
            // convert big to the long value
            long b1 = big.longValueExact();

            // print long value
            System.out.println("long converted value : "
                               + b1);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

BigInteger value : -10000000000000000000
Exception: java.lang.ArithmeticException: BigInteger out of long range

Program 4: To demonstrate longValueExact() method for positive number >9,223,372,036,854,775,807. It will throw Arithmetic Exception

// Java program to demonstrate longValueExact()
// method of BigInteger Class

import java.math.*;

public class GFG {

    public static void main(String[] args)
    {

        // Creating a BigInteger object
        BigInteger big = new BigInteger("10000000000000000000");

        // print value of BigInteger
        System.out.println("BigInteger value : "
                           + big);

        try {
            // convert big to the long value
            long b1 = big.longValueExact();

            // print long value
            System.out.println("long converted value : "
                               + b1);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

BigInteger value : 10000000000000000000
Exception: java.lang.ArithmeticException: BigInteger out of long range

Reference: https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#longValueExact–