Thread: How do I loop with an If statement

The answer to the question posed by your thread title is, You don't. if() and if()/else statements are branching tools that logically determine which path the program will take from a number of possible paths but cannot return execution to the beginning of the if() logic. Loops are for(), while(), and do/while() statements.

What you a trying to do is input validation. If the user provides a number of inputs, validation should be done immediately after each input has been obtained, not after all inputs have been obtained. If you were using multiple methods, I would suggest that a method be used to obtain and validate each input. I suspect you're not using methods beyond the main() method, so then you could use the general form:

// a flag to indicate validity of input
boolean inputValid = false;
while ( !inputValid )
{
    // prompt for and get input from user
 
    // if input is valid, set flag so that loop exits
    if ( a condition that is true if user input is valid )
    {
        inputValid = true;
    }
    else
    {
        // inform the user the input in incorrect
    }
}

Thanks for the response. I actually took a second look at the do loop. I did some trial and error and ended up with this. It works. The only thing is, when the user is prompted for the y/n? The input of y or n goes below the input line and I would like it to be on the same line right after the semi colon. Any one know how I can adjust that.

package assignment2b;
 
import java.util.Scanner;
 
 
public class Assignment2b {
 
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
 
    Scanner in = new Scanner(System.in); // input object
 
 
 
    double loanAmount;                                      // user input
    double interestRate;                                    // user input
    double yearNumber;                                      // user input
    double monthlyPayment;                                  // payment from math.pow
    double finalPayment;                                    // actual payment displayed
    double monthNumber;                                     // number of months
    double monthlyRate;                                     // interest rate by month
 
    String answer = null;                                   // string answer
 
    do {                                                    // opens loop        
 
    System.out.print("Enter loan amount: ");                // Line to input loan amount
    loanAmount = Double.parseDouble (in.nextLine());        // Gets input number
 
 
    System.out.print("Enter rate: ");                       // Line to input rate amount
    interestRate = Double.parseDouble (in.nextLine());      // Gets input number
 
    monthlyRate  = interestRate /100 /12;                   //Convert rate into decimals
 
 
    System.out.print("Enter number years: ");               // Line to input number of years
    yearNumber = Double.parseDouble (in.nextLine());        // Gets input number
 
    monthNumber = yearNumber * 12;                          // Total amount of months  
 
    monthlyPayment = Math.pow(1+monthlyRate , monthNumber) / (Math.pow(1+monthlyRate, monthNumber)-1);
 
    finalPayment = (loanAmount*monthlyRate*monthlyPayment);               // Gives the payment          
 
    if (loanAmount <= 0 || interestRate <=0 || yearNumber <=0)            // incorrect# line
     {       
      System.out.println("\nYou must enter positive numeric data!");
 
    }
    else                                                                  // correct# line
    {    
    System.out.printf("\nThe monthly payment is: $%.2f", finalPayment);   // Monthly payment
    System.out.println();                                                 // Moves build line
    } 
 
     System.out.println("\nWould you like to calculate again (y/n): ");   // prompt to run again
      answer = in.nextLine();                                             // gets answer
    }
    while (answer.equals("y"));                                           // runs program again
 
    }
 
 
    }

println() will add a linefeed at the end of the prompt line. If you don't want the linefeed, use the print() method.

Originally Posted by GregBrannon

println() will add a linefeed at the end of the prompt line. If you don't want the linefeed, use the print() method.

Sorry still learning. Do you have any example?

My memory is fuzzy on exactly which line needs to be modified, so for the line after which a linefeed is not desired, change println() to print(), and you'll have constructed your very own example.

Originally Posted by GregBrannon

My memory is fuzzy on exactly which line needs to be modified, so for the line after which a linefeed is not desired, change println() to print(), and you'll have constructed your very own example.

I've tried this every way I can think of, and I cant the answer to (y/n) to appear on the same line right after the : of the question.

Show the code changes you made for the failed attempt(s). You don't have to show every way you can think of, but the one you think is the best would be nice.

Originally Posted by GregBrannon

Show the code changes you made for the failed attempt(s). You don't have to show every way you can think of, but the one you think is the best would be nice.

Got it! Thanks!

You fixed it then?

Originally Posted by GregBrannon

You fixed it then?

Yep must have been the computer or Netbeans. I tried the System.out.print() again on a different computer and it worked fine. Very frustrating, I knew that was how to do it.