Limits

Unlike in math, where numbers can be arbitrarily big or small, a Java int is "fixed width."

Say you had a piece of paper that was only big enough to write two numbers on.

The only numbers you could write in a base ten system would be those from 0 to 99. You could not write 100 or anything larger.

A Java int is similar except instead of only being able to write 0 to 99 on a piece of paper, a variable that has the type int can represent numbers from -2³¹ to 2³¹ - 1.

If you try to directly write out a number that is outside of that range, Java will not let you.

void main() {
// This will not run
int tooBig = 999999999999;
}

If you do math that should produce a larger number than is representable, the value will "loop around."

void main() {
// This is the value of 2^31 - 1
int atLimit = 2147483647;
// The value will "loop around" to -2^31
int beyondLimit = atLimit + 1;
// This will output -2147483648
System.out.println(beyondLimit);
}

There are other types which can represent a larger range of integers, as well as types which do not have any limits, but for now int is the only one you will need.