Introduction

Programming flowcharts, for Java

A flowchart is a picture of your program's logic. Learn the symbols, see how each flowchart turns into Java code, then check yourself with short quizzes.

Start the lessons Jump to a quiz

What is a flowchart?

A flowchart is a diagram that shows the step-by-step solution to a problem (an algorithm). Each kind of step has its own symbol, and arrows (flow lines) show the order the steps run in.

Programmers draw flowcharts before writing code to:

Plan the logic without worrying about Java syntax yet.
Find mistakes early, like a loop that never ends or a missing case.
Explain the program to someone else (your professor, your groupmates).

Once the flowchart is correct, turning it into Java is mostly translation: each symbol becomes one or more Java statements.

The 5 symbols you'll use most

	Terminal Start / End
	Input / Output `Scanner`, `System.out.println`
	Process Assignments and calculations
	Decision `if`, `while`, loop conditions
	Flow line Order of execution

One problem, three ways

Here's the same problem written as an algorithm, a flowchart, and Java code. Problem: compute the area of a rectangle.

1. Algorithm (pseudocode)

Start
Input length and width
area = length × width
Output area
End

2. Flowchart

3. Java

// Start
Scanner sc = new Scanner(System.in);
// Input
double length = sc.nextDouble();
double width  = sc.nextDouble();
// Process
double area = length * width;
// Output
System.out.println(area);
// End

The three control structures

Every program, no matter how big, is built from only three patterns. Learn to recognize them in a flowchart and you can read (and draw) almost anything on the quiz.

1 · Sequence

Top to bottom

Steps run one after another in a straight line. No diamonds.

2 · Selection

Choose a path

A diamond splits the flow into True/False paths. In Java: if, if-else, switch.

3 · Repetition

Loop back

An arrow goes back up to an earlier step. In Java: while, for, do-while.

Rules for a good flowchart

Exactly one Start and at least one End terminal.
Flow goes top to bottom, left to right. Arrows show any other direction.
Every decision has two exits, labeled True/False (or Yes/No).
Keep the text inside each symbol short: one action per symbol.
Every path must eventually reach End. If one can't, you have an infinite loop.
Flow lines should not cross. Use a connector (small circle) if they would.

How to study for tomorrow

Read the Lessons (about 20 minutes). Use the step-through tracer on the while loop.
Take each quiz. They're 10 questions each and the order is shuffled every time, so retake them until you score 9/10 or better.
Download the cheat sheet for a last look before the quiz, and try the practice worksheet with a classmate.

Heads up: This kit uses the common ANSI/ISO flowchart symbols. If your professor draws something differently (for example a hexagon for for loop setup), follow your professor's notation on the quiz.