Can't use the Same Name in the Same Scope

class CheckingAccount
{
  . . . .
  private int    balance;

  public void processCheck( int  amount )
  {                          
    int amount;    

    incrementUse();
    if ( balance < 100000 )
      amount = 15;                    // which amount ??? 
    else
      amount = 0;                     // which amount ??? 

    balance =  balance -  amount ;    // which amount ??? 
  } 
}

It is a mistake to use the same identifier twice in the same scope. For example, the following is a mistake:

The scope of the formal parameter amount overlaps the scope of the local variable (also named amount), so this is a mistake. This is a different situation than a previous example where two methods used the same name for their formal parameters. In that situation the scopes did not overlap and there was no confusion.