This is the seventh lesson in a series introducing 10-year-olds to programming through Minecraft. Learn more here.
There are several types of variables that are part of the Java language; these are called primitive types. The most important ones for Minecraft are:
char: A single character (e.g. 'a', 'x')
integer: A whole number (e.g. -10, 0, 1, 145). It has a minimum value of -2,147,483,648 and maximum value of 2,147,483,647.
float: A decimal number (e.g. 3.62341, 1.5). Floats in Java are written with an 'f' or 'F' after them. For example:
float dirtHardness = 0.5f;
Most of the expressions we'll use for Minecraft are addition and subtraction:
int x = 5; int y = x - 3; int z = y + 2;
In this case,
y would have a value of 2 and
z would have a value of 4. We can also perform multiplication and division.
There are two ways to write boolean expressions: comparisons and boolean operators.
>: greater than
<: less than
>=: greater than or equal to
<=: less than or equal to
==: equal to
!=: not equal to
= assigns a value to a variable, but
== compares two variables.
int x = 5; int y = 2; boolean isXGreaterThanY = x > y; // true boolean isYLessThanOrEqualToX = y <= x; // true
!: Boolean NOT
&&: Boolean AND
||: Boolean inclusive OR
^: Boolean exclusive OR
We probably won't use
^ very often.
int myAge = 34; int yourAge = 18; int dadsAge = 60; // These all evaluate to true boolean isYoungerThan50 = !myAge > 50; boolean bothOfUsAreYoungerThan50 = myAge < 50 && yourAge < 50; boolean eitherOfUsIsYoungerThan50 = myAge < 50 || dadsAge < 50;
Notice that a single statement can span multiple lines :) As long as you have the semicolon at the end, all is well.