Comparison Operators

Comparison operators allow us to compare two values against one another. A comparison returns a boolean result of either true or false. The table below lists each of the comparison operators and their usages:

A Basic Comparison

In the following example, we compare two variables x and y. We store the result of this comparison in variable z.

var x = 10;
var y = 8;

var z = x > y;
println(z);

What will get printed to the screen? The above comparison, x > y, is evaluating if 10 is greater than 8. Because 10 is indeed greater than 8, z is assigned a value of true. Thus, true will get printed to the screen.

More Practice

Let's get a little more practice. Take a look at the following code segment below. Pay close attention to each comparison and the operator being used.

var a = 3;
var b = 5;
var c = 2;
var d = 3;

var t = a > 0;
var u = a == d;
var v = d >= b;
var w = b > c;
var x = a != d;
var y = d < = a;
var z = 4 < = c;

println("t = " + t);
println("u = " + u);
println("v = " + v);
println("w = " + w);
println("x = " + x);
println("y = " + y);
println("z = " + z);

When we run this code, what boolean values (true or false) will get printed to the screen for variables t through z? See if you can figure it out on your own. The solution is given below.

Solution:

t = true
u = true
v = false
w = true
x = false
y = true
z = false

Comparison Operators in a Program

Suppose we want to write a program which restricts people under a certain height from riding on a roller coaster. For this particular roller coaster, people who are under 4 feet (48 inches) are not allowed on the ride. How would we do this?

var height = readInt("How tall are you (in inches)? ");
var isTallEnough = height >= 48;
println("Can ride on the roller coaster: " + isTallEnough);

Pitfalls

A common mistake is using = when you actually want to use ==. = is used for assignment of variables whereas == is used for comparing the equality of two values.

For example, x = 5 stores the value 5 into the variable x. However, x == 5 tests to see if the value 5 is equal to the variable x and then returns either true or false. They are not the same thing!