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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 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?) . 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 of writing style:

int x=10;
  
// BedingungConditional ohne Klammer-Block, die Bedingung
without brackets 
// gehtthe inconditional diesemwill Fallrun bisuntil zumthe nächstennext Semikolonsemicolon
// dasThe "else" istis ebenfallsoptional optional
if(x == 10)
println("x ist gleich 10");
  
// HierHere is einea Bedinungconditional mitwith mehrerenmultiple Fällencases
// zupay Beachtenattention istto diethe schreibweiseuse vonof 'else if'
if(x == 10)
println("x is istthe same gleichas 10");
else if(x == 9)
println("x is the istsame gleichas 9");
else if(x == 8)
println("x is istthe same gleichas 8");
else
println("x istis nichtnot 10,9 oderor 8");

For the multiple cases, there is a simpler version:

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

Exercise 

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