long Keyword Usage and Examples

Learn everything about the Java long keyword: its syntax, usage, range, memory size, and how it differs from other data types. Includes beginner-friendly examples and detailed outputs.

This reference explains long Keyword Usage and Examples through its syntax, examples and boundaries. Use the linked course lessons when the surrounding Java concepts are unfamiliar.

The long keyword in Java is a primitive data type used to store large integer values. If your program needs to handle numbers beyond the range of int, then long is the ideal choice.

It occupies 64 bits (8 bytes) in memory and can store values from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.

long variableName = value;

• When working with very large numbers, such as financial calculations, file sizes, or time in milliseconds.
• When the value exceeds the maximum range of int (2³¹-1).

public class LongExample1 {
    public static void main(String[] args) {
        long population = 7800000000L;
        System.out.println("World Population: " + population);
    }
}

World Population: 7800000000

Explanation: Notice the L at the end of the number. By default, Java treats whole numbers as int. Appending L tells Java this number should be interpreted as a long.

public class LongExample2 {
    public static void main(String[] args) {
        long bigValue = 2200000000; // Compilation error
        System.out.println(bigValue);
    }
}

error: integer number too large: 2200000000

Explanation: Java assumes numeric literals are int by default. Without the L, the number is too large to be stored in an int, causing a compilation error.

public class LongExample3 {
    public static void main(String[] args) {
        long millisecondsPerDay = 24L * 60 * 60 * 1000;
        System.out.println("Milliseconds in a Day: " + millisecondsPerDay);
    }
}

Milliseconds in a Day: 86400000

Explanation: Using L ensures that at least one operand is a long, so the result is also a long. This avoids overflow when dealing with large products.

If a long variable is declared as a class-level field and not initialized, Java assigns it a default value of 0L.

public class LongExample4 {
    static long count;
    public static void main(String[] args) {
        System.out.println("Default value: " + count);
    }
}

Default value: 0

• long is used for storing large integers beyond the capacity of int.
• Always use L or l suffix to denote a long literal. Prefer uppercase L for readability.
• Default value of an uninitialized class-level long is 0L.
• Mixing int and long in expressions may lead to implicit type conversions.

Check the example’s types, inputs and documented behavior before copying it into an application. Some APIs require external libraries, files or platform services; consult their setup notes.

Related explanations: Java Data Types - Primitive and Non-Primitive, Java Class - Blueprint of Objects, Exceptions in Java Introduction.

Supporting documentation: Official Java learning guide.