deutsche Version

Conditions in a programming language are instructions such as the further program flow. Similar to rail traffic. A that direct the flow of a program. This works a bit like rail traffic: a train travels on a rail until it hits a switch, then the train changes its direction of travel. The same applies to conditions in a program.Conditions therefore  Conditions, therefore, change the course of a program. But according to which criteria is decided how the program process continueshow is the direction actually decided? The answer to this is logical operations based on the Boolean logic . Sounds more complicated than it is. (remember the logic gates exercise?) . We use logical operations in everyday life, here are some examples:

...

• equal to ==
• not equal !=
• greater than >
• less than <
• greater than or equal to >=
• less than or equal to <=
• logical And &&
• logical Or ||

In the code it looks like this looks as follows:

int x = 10;
if(x == 10)
{
   println("x is the same as 10");
}
else
{
   println("x is not the same as 10");
}

...

The syntax of a condition is always:

if([boolischboolean expression])
 {
 // blockcode derthat ausgeführtwill wirdbe wennexecuted derif boolischethe Ausdruckanswer Trueis isttrue
 }
 else
 {
 // blockcode derthat ausgeführtwill wirdbe wennexecuted derif boolischethe Ausdruckanswer Falseis istfalse
 }

Of course, there are also some variants variations of writing style:

int x=10;

 
// BedingungConditional ohne Klammer-Block, die Bedingung
without brackets 
// gehtthe inconditional diesemwill Fallrun bisuntil zumthe nächsten Semikolon
// das else ist ebenfalls optional
next semicolon
if(x == 10)
println("x ist gleich 10");
 

If the first condition is false, we can test new condition with else if. We can keep doing this indefinitely.

int x=10;
  
// Here Hieris einea Bedinungconditional mitwith mehrerenmultiple Fällencases
// zupay Beachtenattention istto diethe schreibweiseuse vonof 'else if'
if(x == 10) {
	println("x ist gleichis the same as 10");
} else if(x == 9) {
	println("x ist gleichis the same as 9");
} else if(x == 8) {
	println("x ist gleichis the same as 8");
} else {
	println("x istis nichtnot 10,9 oderor 8");
}

For the multiple alternative cases, there is a simpler versionalso the switch statement:

int x=10;
switch(x)
{
case 10:
println("x ist gleichis the same as 10");
break;
case 9:
println("x ist gleichis the same as 9");
break;
case 8:
println("x is the istsame gleichas 8");
break;
default:
println("x is istthe same nichtas 10,9 oderor 8");
break;

Exercise

...

 5

Programm a Program a drawing programapp. The color colour can be changed with the buttons '1' - '5'. The left mouse button is draws and the right mouse button is used to erase it.erases the drawing.

A possible solution to exercise 5: 

color myColor = color(255, 0, 0);// red by default

void setup()
{
  size(600, 600);      // def. window size
  noStroke();
  background(255);
}

void draw()
{
  if (mousePressed && mouseButton == LEFT) {
    fill(myColor);
    ellipse(mouseX, mouseY, 15, 15);
  }
    if (mousePressed && mouseButton == RIGHT) {
    fill(255); // white
    ellipse(mouseX, mouseY, 15, 15);
  }
  
}

void keyPressed()
{
  switch(key)
  {
  case '1':
    myColor = color(255, 0, 0);// red 
    break;
  case '2':
    myColor = color(0, 255, 0);// green 
    break;
  case '3':
    myColor = color(0, 0, 255);// blue 
    break;
  case '4':
    myColor = color(0, 0, 0);// black 
    break;
  case '5':
    myColor = color(255, 255, 0);// yellow 
    break;
  default:
    println("wrong key");
    break;
  }
}