Translating Head First Java Examples to Processing

Getting rid of main() when it appears in a TestDrive class

This example appears on page 66 of Head First Java.

class Books {

String title;

String author;

}

class BooksTestDrive {

public static void main() {

Books[] myBooks = new Books[3];

int x = 0;

myBooks[0] = new Books();

myBooks[1] = new Books();

myBooks[2] = new Books();

myBooks[0].title = "The Grapes of Java";

myBooks[1].title = "The Java Gatsby";

myBooks[2].title = "The Java Cookbook";

myBooks[0].author = "bob";

myBooks[1].author = "sue";

myBooks[2].author = "ian";

// The example is using a while loop where it's actually more convenient to use a for loop

// Think about how you'd change this to be a for loop

while (x < 3) {

// We have to convert the print and println's as well

System.out.print(myBooks[x].title);

System.out.print(" by ");

System.out.println(myBooks[x].author);

x = x + 1;

}

}

}

For Processing, this becomes:

class Books {

String title;

String author;

}

Books[] myBooks = new Books[3];

int x = 0;

myBooks[0] = new Books();

myBooks[1] = new Books();

myBooks[2] = new Books();

myBooks[0].title = "The Grapes of Java";

myBooks[1].title = "The Java Gatsby";

myBooks[2].title = "The Java Cookbook";

myBooks[0].author = "bob";

myBooks[1].author = "sue";

myBooks[2].author = "ian";

// The example is using a while loop where it's actually more convenient to use a for loop

// Think about how you'd change this to be a for loop

while (x < 3) {

print(myBooks[x].title);

print(" by ");

println(myBooks[x].author);

x = x + 1;

}

Getting rid of main() when it appears in a regular class (class with state)

This example appears on page 67.

class Triangle {

// The class has class variables (called fields) - this means it's a "real" class (not a

// dummy entry class)

double area;

int height;

int length;

public static void main(String[] args) {

int x = 0;

Tringle[] ta = new Triangle[4];

// The example is using a while loop where it's actually more convenient to use a for loop

// Think about how you'd change this to be a for loop

while (x < 4 ) {

ta[x] = new Triangle();

ta[x].height = (x + 1) * 2;

ta[x].length = x + 4;

ta[x].setArea();

System.out.print("triangle "+x+", area");

System.out.println(" = " + ta[x].area);

x = x + 1;

}

int y = x;

x = 27;

Triangle t5 = ta[2];

ta[2].area = 343;

System.out.print("y = " + y);

System.out.println(", t5 rea = " + t5.area);

}

void setArea() {

area = (height * length) / 2;

}

}

For Processing, this becomes:

class Triangle {

// The class has class variables (called fields) - this means it's a "real" class (not a

// dummy entry class)

double area;

int height;

int length;

void setArea() {

area = (height * length) / 2;

}

}

int x = 0;

Triangle[] ta = new Triangle[4];

// The example is using a while loop where it's actually more convenient to use a for loop

// Think about how you'd change this to be a for loop

while (x < 4 ) {

ta[x] = new Triangle();

ta[x].height = (x + 1) * 2;

ta[x].length = x + 4;

ta[x].setArea();

print("triangle "+x+", area");

println(" = " + ta[x].area);

x = x + 1;

}

int y = x;

x = 27;

Triangle t5 = ta[2];

ta[2].area = 343;

print("y = " + y);

println(", t5 area = " + t5.area);