Learn How to Use Java IF and Nested IF Conditions

Java provides two selection statements: if and switch. These statements let you control the course of your program’s execution based upon conditions known particularly during run time. You will be pleasingly amazed by the power and versatility contained in these two statements.

IF Statement in Java

The if statement is examined in detail in this article. The if statement is Java’s conditional branch statement. It can be used to route program execution using two different paths. Here is the usual form of the if statement:

if (condition) statement1;
 else statement2;

Here, every statement may be a single statement or a compound statement contained in curly braces. The condition is any expression that gives back a boolean value. The else clause is optional.

The if acts like this: If the condition is true, then statement1 is executed. Otherwise, statement2 (if it exists) is performed. In no circumstance will both statements be executed. For example, consider the following:

     int c, d;
     // ...
     if(c < d) c = 0;
     else d = 0;

Here, if c is less than d, then c is set to zero. Otherwise, d is set to zero. In no circumstance are they both set to zero.

Generally, the expression used to control the if will include the relational operators. Nevertheless, this is not technically mandatory. It is possible to control the if employing a single boolean variable, as presented in this code fragment:

Always Remember, only one statement can appear directly after the if or else. If you wish to include more statements, you’ll need to create a block, as in this fragment:

int bytesAvailable;
// ...
if (bytesAvailable > 0) {

ProcessData();

bytesAvailable -= n;
} else

waitForMoreData();

Here, both statements in the if block will execute if bytesAvailable is more significant than zero. Some programmers find it helpful to insert the curly braces while using the if, even when there is one statement in each clause.

A nested if is an if statement that is the target of another if or else. When you nest ifs, the foremost thing to remember is that an else statement always refers to the nearest if statement that is inside the same block as the else and that is not already associated with an else. Here is an example:

if(i == 10) {
if(j < 20) a = b;
if(k > 100) c = d; // this if is
else a = c; // associated with this else

}
else a = d; // this else refers to if(i == 10)

As the comments show, the final else is not associated with if(j<20) because it is not in the same block. Instead, the final else is related with if(i==10). The inner else points to if(k>100) because it is the nearest if within the same block.

The if-else-if Ladder

A usual programming construct that is based upon a sequence of nested ifs is the if-else-if ladder. It looks like this:

if(condition) statement;

else if(condition) statement;

else if(condition) statement;
.
.
. else

statement;

The if statements run from the top down. As soon as one of the conditions checking the if is true, the statement linked with that if is executed, and the rest of the ladder is avoided. If none of the conditions is true, then the final else statement will be performed.