Imagine we’re writing a program that enrolls students in courses.
- If a student has completed the prerequisites, then they can enroll in a course.
- Else, they need to take the prerequisite courses.
They can’t take Physics II without finishing Physics I.
We represent this kind of decision-making in our program using conditional or control flow statements. Before this point, our code runs line-by-line from the top down, but conditional statements allow us to be selective in which portions will run.
Conditional statements check a boolean
condition and run a block of code depending on the condition. Curly braces mark the scope of a conditional block similar to a method or class.
Here’s a complete conditional statement:
if (true) { System.out.println("Hello World!"); }
If the condition is true
, then the block is run. So Hello World!
is printed.
But suppose the condition is different:
if (false) { System.out.println("Hello World!"); }
If the condition is false
, then the block does not run.
This code is also called if-then statements: “If (condition)
is true
, then do something”.
Instructions
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