Long longValue() Method in Java

The java.lang.Long.longValue() is an inbuilt method of the Long class in Java which returns the value of this Long object as a long after the conversion.
Syntax:

public long longValue()

Parameters: This method does not take any parameters.
Return Value: This method will return the numeric value represented by this object after conversion to long type.
Examples:

Input: 5366623
Output: (Long) 5366623

Input: -6723887
Output: (Long) -6723887
Explanation:
When the number is passed in this object it will convert that 
to long and gives the value like,
Long lobject = new Long(5366623)
It will return 5366623 as long.

Below programs illustrate the working of java.lang.Long.longValue() method. 
Program 1: For a positive number.  

java

// Java program to illustrate the
// java.lang.Long.longValue() method

import java.lang.*;

public class Geek {

    public static void main(String[] args)
    {

        Long lobject = new Long(77387187);

        // It will return the value of this Long as a long
        long nl = lobject.longValue();
        System.out.println("The Value of nl as long is = " + nl);

        Long lobject2 = new Long(-6723887);

        // It will return the value of this Long as a long
        long nl2 = lobject2.longValue();
        System.out.println("The Value of nl2 as long is = " + nl2);
    }
}

Output:

The Value of nl as long is = 77387187
The Value of nl2 as long is = -6723887

Program 2: For a very large no. 
// It will produce compile time error. 

java

// Java program to illustrate the
// java.lang.Long.longValue() method
import java.lang.*;

public class Geek {

    public static void main(String[] args)
    {

        Long lobject = new Long(97387717187);

        // Very large number will produce compile errors
        long nl = lobject.longValue();
        System.out.println("The Value of nl as long is = " + nl);
    }
}

Output:

prog.java:9: error: integer number too large: 97387717187
    Long lobject = new Long(97387717187);
                            ^
1 error

Reference: https://docs.oracle.com/javase/7/docs/api/java/lang/Long.html#longValue()