loanrepay.java

a Java program that reads in the following values from the standard input device (i.e. Keyboard) an

import java.util.Scanner;
public class LoanRepay {

	public static void main(String[] args) {
		double repayment,loanAmount;
		int interest,wholeYear,month;
		String reUse;//store the user command of whether reuse the program. 
		boolean correctInput = true;//control the loop of reusing the program.
		Scanner keyboard = new Scanner(System.in);
		System.out.println("Please input the amount of loan");
		System.out.println("without dollar sign.");
		loanAmount = keyboard.nextDouble();
		System.out.println("Please input the annual interst rate");
		System.out.println("expressed as an integer. (e.g. 10 which means 10%)");
		interest = keyboard.nextInt();
		System.out.println("Please input the number of whole Years");
		System.out.println("follow by the number of Months.");
		wholeYear = keyboard.nextInt();
		month = keyboard.nextInt();
		if (loanAmount < 0)
		{
		    System.out.println("Some error message for the invalid amount!");
		    correctInput = false;
		};//identify the illegal input and display the error message.
		if (interest < 0)
		{
			System.out.println("Some error message for the invalid interest rate!");
			correctInput = false;
		};//identify the illegal input and display the error message.
		if (wholeYear < 0)
		{
			System.out.println("Some error message for the invalid year(s)!");
			correctInput = false;
		};//identify the illegal input and display the error message.
		if (month <0)
		{
			System.out.println("Some error message for the invalid month(s)!");
			correctInput = false;
		};//identify the illegal input and display the error message.
		if (correctInput)
		{
		    System.out.printf("The loan is $ %.2f",loanAmount);
		    System.out.printf(" at %d%% interest. %n",interest);
		    System.out.printf("over %d year(s) %d month(s).%n",wholeYear,month);		    
		    double percentage = (double) interest/100;//computing the real interest for calculating
		    double temporary1,temporary2,temporary3;//temporary variables to make the calculation more simple.
		    temporary1 = Math.pow(1+percentage, wholeYear);
		    temporary2 = loanAmount*percentage*temporary1*(12+percentage*month);
		    temporary3 = (temporary1-1)*(12+percentage*month)+percentage*month;
		    repayment = temporary2/(12*temporary3);//computting the repayment.
		    System.out.printf("The monthly repayment is $ %.2f%n",repayment);		    
		    System.out.println("Do you want to reuse the service?");
		    System.out.println("input Yes to restart, or other keys to exit.");
		    reUse = keyboard.next();//load the user command.
		    if (reUse.equalsIgnoreCase("Yes"))
            {
		    	System.out.println();
		    	LoanRepay.main(args);//restart the program.
            } 
		    else
		    	System.out.println("Thanks for using LoanRapaymentCalculation!");
		    
		}
		else
		{
			System.out.printf("%nPlease reinput the appropriate numbers!%n");
			LoanRepay.main(args);  
		};//automatically restart the program because of the inappropriate input.
	
	}

}