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Special Effects and Game Development in Java(TM) - IF-statements

by Anibal Wainstein

1.4.3 IF-statements

An "if" statement is one of the fundamental commands in Java. With the if-statement you can test a boolean statement and then execute different program code depending if it is true or not (with the ELSE-statement):

if(a > b)
{
    String r = "A is greater than B";
}
If you want to execute other code if the statement is not true then you can add ELSE:
if(a > b)
{
    String r = "A is greater than B";
}
else
{
    String r = "A is not greater than B";
}

1.4.4 FOR loops

A for loop consists of a bit of code where the "for" command states how many times the code should be executed. It is defined in the following way:

for (init; condition; incrementation)
{
code that will be executed
}
The type of loop that will used about 90% of the time in this course is:
for (int i=0; i<5; i++)
{
    code that will be executed
}
What will happen here is that the loop will count to four and store the subsequent values in the variable "i". The condition "i<5" states that "i" must be less than 5, that is, "i" is not allowed to receive greater values than 4. The expression "i++" will increase "i" until we reach 4. You can also count down in for-loops:
for (int i=5; i>0; i--)
{
    code that will be executed }
The variable "i" will start with 5 and count down to 1. The expression "i--" decreases "i" with 1 each time, but the condition "i>0" makes sure that "i" never reaches 0.

1.4.5 WHILE loops

The while loop works in a different way. It executes code as long as an expression is true:

while (condition)
{
    code that will be executed
}
The same functionality in the for loop that we had in the last section can be done with a while loop:
int i = 0;
while (i<4)
{
    i++;
}
Note that here we cannot write "i<5" because the incrementation happens after the comparison. The expression above will count from 0 to 4 with "i". The decrementation example in the last section can be done like this:
int i = 5;
while (i>0) {     i--; }

That is it for now! In the next chapter you will learn how to program and compile your first applet.



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