Learn how to declare, initialise and print int variables in Java. This program prints the range of int using Integer.MAX_VALUE and Integer.MIN_VALUE. It also shows that int overflow wraps around without any error, and how to use underscores to make large numbers easier to read.
int data typeint uses 4 bytes (32 bits) and stores values from -2,147,483,648 to 2,147,483,647Integer.MAX_VALUE and Integer.MIN_VALUEint + int gives an int, so no cast is neededint to longmain() methodSystem.out.println()byte and short data typesInt data type is a 32-bit signed two's complement integer.
Minimum value is - 2,147,483,648 (-2^31)
Maximum value is 2,147,483,647(inclusive) (2^31 -1)
Integer is generally used as the default data type for integral values unless there is a concern about memory.
The default value is 0
Example: int a = 100000, int b = -200000
Environment: JDK (Windows, Linux, macOS)
Execution command:
javac IntDataType.java
java IntDataTypepublic class IntDataType {
public static void main(String[] args) {
// Declare and initialise int variables
// int is the default type for whole numbers in Java
int a = 10000;
int b = -5000;
System.out.println("a = " + a);
System.out.println("b = " + b);
// Range of the int data type
System.out.println("Max int value = " + Integer.MAX_VALUE);
System.out.println("Min int value = " + Integer.MIN_VALUE);
// int + int stays an int, so no cast is needed
int sum = a + b;
System.out.println("sum = " + sum);
// Overflow: going past the maximum wraps around silently
int overflow = Integer.MAX_VALUE + 1;
System.out.println("Integer.MAX_VALUE + 1 = " + overflow);
// Underscores make large numbers easier to read (Java 7+)
int population = 1_500_000;
System.out.println("population = " + population);
}
}No input required
a = 10000
b = -5000
Max int value = 2147483647
Min int value = -2147483648
sum = 5000
Integer.MAX_VALUE + 1 = -2147483648
population = 1500000
int is the most commonly used integer data type in Java. It stores whole numbers
in 4 bytes (32 bits) of memory, with a range of -2,147,483,648 to 2,147,483,647.
Every whole-number literal you write, such as 10000, is an int by default.
int for everyday whole numbers such as counters, loop variables, ages and marks. Switch to long only when values can go beyond about 2.1 billion.
The default type for whole numbers.
int a = 10000;
int b = -5000;
int is the data type, and a and b are the variable names. No suffix is needed, because whole-number literals are already int.
Text and values joined with +.
System.out.println("a = " + a);
System.out.println("b = " + b);
The + operator joins the label and the value, so the output is a = 10000 and b = -5000.
The largest and smallest values.
System.out.println("Max int value = " + Integer.MAX_VALUE);
System.out.println("Min int value = " + Integer.MIN_VALUE);
Integer is the wrapper class for int. With 32 bits, an int can store $$2^{32}$$ different values, from $$-2^{31}$$ to $$2^{31} - 1$$.
No cast is needed.
int sum = a + b;
System.out.println("sum = " + sum);
Unlike byte and short, adding two int values gives an int. So the result 5000 is stored directly, with no cast.
Going past the maximum wraps around.
int overflow = Integer.MAX_VALUE + 1;
System.out.println("Integer.MAX_VALUE + 1 = " + overflow);This compiles and runs without any error, but the result is wrong. The value goes past the maximum and wraps around to the minimum: $$2147483647 + 1 \rightarrow -2147483648$$ This is a common source of bugs in calculations with large numbers.
Easier to read, same value.
int population = 1_500_000;
System.out.println("population = " + population);
From Java 7, you can place underscores between digits. The compiler ignores them, so 1_500_000 is the same as 1500000, and the underscores don't appear in the output.
| Property | Value |
|---|---|
| Size | 4 bytes (32 bits) |
| Range | -2,147,483,648 to 2,147,483,647 |
| Default value (fields) | 0 |
| Literal suffix | None (default for whole numbers) |
| Wrapper class | Integer |
| Type | Size | Range |
|---|---|---|
byte |
1 byte | -128 to 127 |
short |
2 bytes | -32,768 to 32,767 |
int |
4 bytes | -2,147,483,648 to 2,147,483,647 |
long |
8 bytes | About ±9.22 × 1018 |
a = 10000
b = -5000
Max int value = 2147483647
Min int value = -2147483648
sum = 5000
Integer.MAX_VALUE + 1 = -2147483648
population = 1500000int big = 3000000000; gives the error integer number too large. Use long big = 3000000000L; instead.
int result = 50000 * 50000; compiles but gives a wrong negative number, because the real answer is bigger than the int range.
_1000, 1000_ and 1_.5 aren't allowed. Underscores can only go between digits.
Math. Time: O(1)
Space: O(1)
First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.
Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.
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