int

In Java, an int is used to store whole numbers (numbers without decimals).

An int:

• Has a fixed size of 32 bits (4 bytes) in memory
• Can store values from -2,147,483,648 to 2,147,483,647

Examples

int count = 19;
int score = -5;
int temperature = 0;

Integer types in Java

Java has four integer primitive types:

• byte (1 byte)
• short (2 bytes)
• int (4 bytes)
• long (8 bytes)

Why is int used most often?

int is the default choice for whole numbers because:

• Its range is large enough for most programmes
• It uses a reasonable amount of memory (4 bytes)
• It is fast and efficient for Central Processing Units (CPUs) to process

Primitive type

int is a primitive data type. Primitive types are simple, fast, and memory‑efficient.

This means:

• It stores its actual value directly in memory
• It does not store a reference to an object
• It has no methods of its own

If you change the value of a long variable, the old value is replaced by the new:

int a = 15;  // 'a' is 15
a = 20;       // Now 'a' is replaced by 20

The Integer wrapper class

Although int itself has no methods, Java provides a wrapper class called Integer.

The Integer class:

• Wraps an int value inside an object
• Provides useful constants and methods

Integer methods

Useful Integer constants

Converting values

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

int num = Integer.parseInt("12345"); // Returns 12345

Converting an int to a String

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

Comparing Integer values

compare(int a, int b)

int result = Integer.compare(12, 23);

compareTo(Integer other)

Integer x = 12; // has to be Integer. int will generate an error
Integer y = 23;

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)

Integer x = 12; // has to be Integer. int will generate an error
Integer y = 15;

x.equals(y); // true

Math helper methods

Summary

• int stores whole numbers
• It is a 32‑bit primitive type
• It is fast, memory‑efficient, and widely used
• It has no methods, but the Integer wrapper provides many utilities

Further Reading

• Java Integer class
• Java primitives