Instant isBefore() method in Java with Examples

isBefore() method of an Instant class checks if this instant timeline position is before the instant passed as parameter or not. If this instant timeline position is before the instant passed as a parameter then the method will return true else false. The comparison is based on the time-line position of the instants. Syntax:

public boolean isBefore(Instant otherInstant)

Parameter: This method takes a parameter otherInstant which is the other instant to compare to. It should not be null. Returns: This method returns true if this instant is before the specified instant. Exception: This method throws NullPointerException if otherInstant is null. Below programs illustrate the isBefore() method: Program 1:

Java

// Java program to demonstrate
// Instant.isBefore() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a Instant object
        Instant instant1
            = Instant.parse("2018-12-30T09:24:54.63Z");

        // create other Instant
        Instant instant2
            = Instant.parse("2018-12-31T01:34:00.63Z");

        // print instances
        System.out.println("Instance 1: " + instant1);
        System.out.println("Instance 2: " + instant2);

        // check if instant1 is before instant2
        // using isbefore()
        boolean value = instant1.isBefore(instant2);

        // print result
        System.out.println("Is Instant1 before Instant2: "
                           + value);
    }
}

Output:

Instance 1: 2018-12-30T09:24:54.630Z
Instance 2: 2018-12-31T01:34:00.630Z
Is Instant1 before Instant2: true

Program 2:

Java

// Java program to demonstrate
// Instant.isBefore() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a Instant object
        Instant instant1
            = Instant.parse("2018-11-27T09:24:54.63Z");

        // create other Instant
        Instant instant2 = Instant.now();

        // print instances
        System.out.println("Instance 1: " + instant1);
        System.out.println("Instance 2: " + instant2);

        // check if instant1 is before instant2
        // using isBefore()
        boolean value = instant1.isBefore(instant2);

        // print result
        System.out.println("Is Instant1 before Instant2: "
                           + value);
    }
}

Output:

Instance 1: 2018-11-27T09:24:54.630Z
Instance 2: 2018-11-27T04:55:36.127Z
Is Instant1 before Instant2: false

Program 3: To show Exception thrown by isBefore() 

Java

// Java program to demonstrate
// Instant.isBefore() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a Instant object
        Instant instant1 = Instant.parse("2018-10-30T19:34:50.63Z");

        // create other Instant
        Instant instant2 = null;

        try {

            // print instances
            System.out.println("Instance 1: " + instant1);
            System.out.println("Instance 2: " + instant2);

            // check if instant1 is before instant2
            // using isBefore()
            boolean value = instant1.isBefore(instant2);
        }
        catch (Exception e) {
            // print result
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Instance 1: 2018-10-30T19:34:50.630Z
Instance 2: null
Exception: java.lang.NullPointerException

References: https://docs.oracle.com/javase/10/docs/api/java/time/Instant.html#isBefore(java.time.Instant)