嵌套if-else語句合法的，這意味著可以使用一個if，else if在另一個 if 或 else if 聲明裡麵中。

語法

嵌套if語句的語法如下：

if( boolean_expression 1)
{
   // Executes when the boolean expression 1 is true
   if(boolean_expression 2)
   {
      // Executes when the boolean expression 2 is true
   }
}

可以嵌套 else if...else在類似if語句的方式。

例子：

#include <iostream>
using namespace std;
 
int main ()
{
   // local variable declaration:
   int a = 100;
   int b = 200;
 
   // check the boolean condition
   if( a == 100 )
   {
       // if condition is true then check the following
       if( b == 200 )
       {
          // if condition is true then print the following
          cout << "Value of a is 100 and b is 200" << endl;
       }
   }
   cout << "Exact value of a is : " << a << endl;
   cout << "Exact value of b is : " << b << endl;
 
   return 0;
}

當上述代碼被編譯和執行時，它產生了以下結果：

Value of a is 100 and b is 200
Exact value of a is : 100
Exact value of b is : 200