Understanding Nested If-Else Statements

Here is a model for an if if statement with multiple mutually exclusive alternatives: if(condition1) { } else if(condition2) { } else { }

Any number of else if It can be a useful programming practice to end with a simple else This final else the if ifs and else if Sometimes there is no separate statement or block of statements that needs to be executed in the default case. else ifs can be used. else. else is the default case if none of else ifs hold true.

If so, then the else immediately by a semicolon or by a pair of braces containing nothing. This may seem redundant, but it can serve as a helpful reminder that the default case, after having checked all previous cases, is to do nothing. else can be followed

This structure can be used for a mutually exclusive set of discrete cases as illustrated by the following: if(x == 1) { // do something } else if(x == 2) { // do something else } else { // do yet something else if x is // neither 1 nor 2 }

Notice that it is also useful for handling sequences of numerical values, either ascending or descending: if(x <= 1.0) { // do something } else if(x <= 2.0) { // executed for values of x > 1.0 and <= to 2.0 } else if(x <= 3.0) { // executed for values of x > 2.0 and <= to 3.0 } else { // executed for values of x > 3.0 }

In general there are no restrictions on where if if statements can appear in program code. They can occur within the pair of braces delimiting any valid block. In particular, an if if statement and its else else if of code that belongs to another if if, else else if When this occurs it is known as a nested if if. else or else if statements can appear within a block else, or else if statement.

The nesting refers to the pattern of pairs of matched braces occurring within other pairs of matched braces. For ease of reading, it is recommended that each pair be indented one tab from the pair that contains it. The model when nested only one level deep would look like this:

if(condition1) { if(condition2) { statement1 is executed if condition1 is true and condition2 is true. statement2 is executed if condition1 is true and condition2 is not true. statement3 is executed if condition1 is not true and condition3 is true. statement4 is executed if condition1 is not true and condition3 is not true. statement1; } else { statement2; } } else { if(condition3) { statement3; } else { statement4; } }