Java Condition

So far, we have only seen programs run straight from the start to finish. Hence, that is not always the case. As a program
gets more and more complex, often time we would have to deal with decision making. Without any further notice, let me introduce
two very important decision making tool that comes with java condition. The two tools are the if statement and switch statement. The two
statements rely on the use of boolean expressions, which is true or false. The boolean expression can be very complicated, however we use simple expressions that compare the value of a variable with the value of some other variable. This comparison uses one of the relational operators. All these operators are binary operators which work on two operands.

Example

Assume we have the following statements initialized

int i = 5;
int j = 10;
int k = 6;
 

now, let say we have the following:

Expression            Value            Explanation

i == 5                    true              The value of i is 5

i == 10                  false              The value of i is not 10.

i > 3                      true               i is 5, which is greater than 3

k > i + j                 false              k is 6, i + j is 15

Note: the relational operator that test for equality is two equal signs in a row ( == ). A single equal sign is the
         assignment operator.

    if( i == 5) is not the same as if ( i = 5)

Java if statements

In most cases, an if statement lets us execute a single statement or a block of statements only if a boolean expression
evaluates to be true. The if statement has a basic form looks like this

if ( boolean - expression )
    statement...

Example

int x = 0;

if ( y > 10 )
    x = 4;

In the example above, we have x initialized to 0, then we will assign 4 to x only if the expression y > 10 is true.

Java if-else statements

An if-else statement adds an additional element to a basic if statement. The else block execute if the boolean expression
is not true. It's the basic following format.

if ( boolean-expression)
    statement

else
    statement

Example

int commission;

if( sales >= 1000)
    commission = 0.03;

else
    commission = 0.05;

In the example above, the commission is set to 3% if sales is greater than or equal to 1000. If the sales is less than 1000,
the commission is set to 5%.

We can have a nested if-else statement by using the else-if statement. Basically, it's a series of if-else statements
with another if-else statements in each else part.

Example

int y = 0;

if ( x == 10)
    y = 1;

else if ( x > 10)
    y=3;

else if( x < 3)
    y = 5;

else
    y = 4;

Logic Operator