long

In Java, a long is a primitive data type that is used to store whole numbers, which can be either positive or negative. It has a fixed size of 64 bits (8 bytes), meaning it can hold much larger values than other integer types like int. It can store numbers:

From: -9,223,372,036,854,775,808
To: 9,223,372,036,854,775,807

Example of using long

long count = 100L;   // Correct way to declare a long (use the L suffix)

When to use long:

Use long when the value exceeds the range of an int (which is from -2147483648 to 2147483647)
For example, very large numbers like population counts, financial transactions, or timestamps

Primitive type

A long is a primitive type. This means that it directly stores the value in memory, not a reference to the value. If you change the value of a long variable, the old value is replaced by the new:

long a = 15L;  // 'a' is 15
a = 20L;       // Now 'a' is replaced by 20

Long wrapper class

Even though long is a primitive type, there’s a corresponding wrapper class called Long This class provides useful methods to work with long values.

Useful Long constants

Constant	Example	Result
MAX_VALUE	Long.MAX_VALUE	Returns largest possible long value (9223372036854775807)
MIN_VALUE	Long.MIN_VALUE	Returns Smallest positive long value (-9223372036854775808)
SIZE	Long.SIZE	Returns size of a long in bits (64)
BYTES	Long.BYTES	Returns size of a long in bytes (8)

Converting values

Converting numeric String to long. If the String is not numeric (e.g. "hello"), Java throws a
NumberFormatException.

long num = Long.parseLong("12345"); // Returns 12345

Converting a long to a String

String text = Long.toString(12345L); // Returns "12345"

Comparing Long values

compare(long a, long b)

int result = Long.compare(12345L, 23456L);

compareTo(Long other)

Long x = 12345L;
Long y = 23456L;

x.compareTo(y);

Both compare and compareTo return these values:

0 → if values are equal
-1 → if first is less than second
1 → first is greater than second

equals(Object obj)

Long x = 12345L;
Long y = 12345L;

x.equals(y); // true

Math helper methods

Method	Example	Result
max(long a, long b)	Long.max(12L, 15L)	Returns the larger value
min(long a, long b)	Long.min(12L, 15L)	Returns the smaller value
sum(long a, long b)	Long.sum(12L, 15L)	Returns the sum of the two values

Summary

Long stores whole numbers using 64 bits (8 bytes)
Must use L suffix when assigning values
It’s a primitive type
Use Long wrapper class methods for conversions, comparisons, and constants
Prefer int unless you need long