The Art of Clean Code

The Art
of
Clean Code
The Basics

Yael Zaritsky-Peretz
Developer @ CI team @ Wix

Over
90 million
users
Wix
Over
1000
employees
~400
developers

First Feature - Code
public class MyConsole {
public static void go() throws IOException {
BufferedReader inputReader = new BufferedReader(new
InputStreamReader(System.in));
while (true) {
System.out.print("> ");
System.out.println(inputReader.readLine());
}
}
}
while (true) {
}
}
}
while (true) {
}
}
}

BufferedReader inputReader =
new BufferedReader(new InputStreamReader(System.in));
while (true) {
System.out.println("Please enter one of ... sum / copycat");
String input = inputReader.readLine();
if ("copycat".equals(input)) {
System.out.print(">");
}
while (true) {
System.out.println("Please enter one of ... sum / copycat");
}
Second Feature - Code
else if ("sum".equals(input)) {
System.out.println("Enter numbers to sum...");
String nToSIn = inputReader.readLine();
String[] nToS = nToSIn.split(" ");
String str = "Sum of ";
int sum = 0;
for (int i = 0; i < numbersToSum.length; i++) {
str += nToS[i] + ", ";
sum += Integer.parseInt(nToS[0]);
}
str = str.substring(0, str.length() - 2);
str += "is " + sum;
System.out.println(str);
}…}
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}…}
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}…}
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}…}
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}…}
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}…}
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}…}

while (true) {
System.out.println("Please enter one of … sum/copycat");
// print a line from the user
}
// read numbers separated by space and print their sum
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}
}
}

Agenda
● What is Clean Code?
● Example
● Some Basic Rules
● Culture

public class NumberTest {
@Test
public void testMultiplyByTwo() {
assertThat(Number.multiplyByTwo(2),is(4));
}
}
public class Number {
public static int multiplyByTwo(int number) {
return number;
}
}
@Test
}
}
return number;
}
}
@Test
}
}
return number;
}
}

@Test
}
}
return number * 2;
}
}
@Test
}
}
return number * 2;
}
}

BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));
while (true) {
System.out.println("Please enter one of the following actions: sum / copycat");
} else if ("sum".equals(input)) {
System.out.println("Enter numbers to sum, separated by space. For example: '233 67 8 456086'");
int sum = 0;
for (int i = 0; i < nToS.length; i++) {
str += nToS[i] + ", ";
}
str += "is " + sum;
}
}
}
while (true) {
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}
}
}
while (true) {
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}
}
}

int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}

Make sure that func("3 3") returns "Sum of 3, 3 is 6"

int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}
String str = NumbersToSum.getOutputString(nToSIn);
}

public class NumbersToSum {
public static String getOutputString(String … nToSIn) {
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
return str;
}}
}

@Test
public void testGetOutputStringForSingleNumber() {
assertThat(NumbersToSum.getOutputString("3 3"),
is("Sum of 3, 3 is 6"));
}

int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
return str;
}
}
int sum = 0;
str += nToS[i] + ", ";
}
str += " is " + sum;
return str;
}
}

int sum = 0;
str += nToS[i] + ", ";
}
return str;
}
}
}
String numbersToSumInput = inputReader.readLine();
String str = NumbersToSum.getOutputString(numbersToSumInput);
}
String str = NumbersToSum.getOutputString(numbersToSumInput);
}
int sum = 0;
str += nToS[i] + ", ";
}
return str;
}
}
public static String getOutputString(String … numbersToSumInput) {
String[] nToS = numbersToSumInput.split(" ");
int sum = 0;
str += nToS[i] + ", ";
}
return str;
}
}
int sum = 0;
str += nToS[i] + ", ";
}
return str;
}
}
String[] numbersToSum = numbersToSumInput.split(" ");
int sum = 0;
str += numbersToSum[i] + ", ";
sum += Integer.parseInt(numbersToSum[0]);
}
return str;
}
}

int sum = 0;
}
return str;
}
}

@Test
public void testGetOutputString() {
assertThat(NumbersToSumPrinter.getOutputString("3 231"),
is("Sum of 3, 231 is 234"));
}
@Test
public void testSumOfMoreThanOneNumber() {
assertThat(NumbersToSum.sum(3, 231),
is(234));
}

public class NumbersToSumPrinter {
public static String getOutputString(String numbersToSumInput) {
}
int sum = NumbersToSum.sum(intArrayFromStrings(numbersToSum));
return str;
}
}

public static int sum(int ... numbersToSum) {
int sum = 0;
sum += numbersToSum[0];
}
return sum;
}
}

public static int sum(int ... numbersToSum) {
int sum = 0;
sum += numbersToSum[i];
}
return sum;
}
}

while (true) {
System.out.println("Enter numbers to sum ...");
int sum = 0;
str += nToS[i] + ", ";
}
str += "is " + sum;
}
}
}

public void go() throws IOException {
while (true) {
System.out.println("Please enter one … sum / copycat");
String str = NumbersToSumPrinter.getOutputString(numbersToSumInput);
}
}
}
}

while (true) {
}
}
}
}
while (true) {
}
}
}
}

while (true) {
waitForInputAndCopy(inputReader);
}
}
}
private void waitForInputAndCopy(BufferedReader inputReader) throws IOException {
}
}

while (true) {
waitForInputAndCopy(inputReader);
waitForInputAndSumNumbers(inputReader);
}
}
}
private void waitForInputAndSumNumbers(BufferedReader inputReader) throws IOException {
}
private void waitForInputAndCopy(BufferedReader inputReader) throws IOException {
}
}

Use Pronounceable, Meaningful Names
int sum = 0;
str += nToS[i] + ", ";
}
vs.
int sum = 0;
}

Do Only One Thing
FUNCTIONS / CLASSES / MODULES SHOULD DO ONE THING.
THEY SHOULD DO IT WELL.
THEY SHOULD DO IT ONLY.
while (true) {
}
}

Formatting
int sum = 0;
}
return str;
}
}
int sum = 0;
}
return str;
}
}
int sum = 0;
}
return str;
}
}

DO NOT Treat Test Code Differently

Insights
● Reading Code is Hard
● Code Rots

Refactor Until Your Code is Clean
● Hard to Get Done Right on First Try
● Reading clean code should make you smile
the way a well-crafted music box or well-designed car would

Leave the Campground
Cleaner Than You’ve Found it

● Change one variable name for the better,
● Break up one function that’s a little too large,
● Eliminate one small bit of duplication
The cleanup doesn’t have to be something big:

How YOU can take it from here
● Make it a priority
● It seems to take longer
● Read / see about it
● Talk to your peers

Yael Zaritsky yaelzyaelz@wix.com
yaelzaritsky@gmail.com

Thank You
Yael Zaritsky yaelzyaelz@wix.com
yaelzaritsky@gmail.com

Sources
Clean Code (pdf)
GOOS style TDD by Example - Sagy Rozman
Cultural Learning of Testing - Gil Tayar
Finding Your Organization’s Code Deodorant - Ittai Zeidman

private static int[] intArrayFromStrings(String[] numbersToSum) {
int[] intArray = new int[numbersToSum.length];
for(int i=0 ; i<numbersToSum.length ; i++) {
intArray[i]=Integer.parseInt(numbersToSum[i]);
}
return intArray;
}
}

The Art of Clean Code

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