Question

//by :tlc

import java.util.Scanner;
public class assignment2 {
public static int t1;
public static int t2;
public static int x;
public static int y1;
public static int m1;
public static int d1;
public static int y2;
public static int m2;
public static int d2;
public static void date1() {

Scanner scanner  = new Scanner (System.in);

System.out.println("Please enter the first date \n");
System.out.println ("Please enter the year: "); 
y1=scanner.nextInt();

System.out.println("Please enter the month: ");
m1=scanner.nextInt();

System.out.println("Please enter the day: \n");
d1=scanner.nextInt();

}
public static void date2() {
Scanner scanner  = new Scanner (System.in);

System.out.println("Please enter the second date \n");
System.out.println ("Please enter the year: "); 
y2=scanner.nextInt();

System.out.println("Please enter the month: ");
m2=scanner.nextInt();

System.out.println("Please enter the day: \n");
d2=scanner.nextInt();

}
public static void finaldate() {
x = Math.abs(t1-t2);
}
public static void main(String[] args) {    
date1();
    if (m1==1 + 3 + 5 + 7 + 8 + 10 + 12){
        t1 = ((365*y1)+d1+31);}
        else 
        if (m1==2) {
        t1 = ((365*y1)+d1+28);}
        else
        if (m1==4 + 6 + 9 + 11); {
        t1 = ((365*y1)+d1+30);}

 date2();
    if (m2==1 + 3 + 5 + 7 + 8 + 10 + 12){
        t2 = ((365*y2)+d2+31);}
        else 
        if (m2==2) {
        t2 = ((365*y2)+d2+28);}
        else
        if (m2==4 + 6 + 9 + 11); {
        t2 = ((365*y2)+d2+30);}
 finaldate();

 System.out.println("The difference between the two dates is: " + x + " days.");

}
}

How would I set a catch a false input (ex: not a integer) and have the program display an error message followed by a loop that would return to the beginning of the program? I’ve been struggling with this for a while now.

All help appreciated! 🙂

Answer 1

there are 2 way depending on how the control flow is managed

with exceptions as control flow (the case with Scanner)

while(true){
    try{
        y1=scanner.nextInt();
        break;//success break out of loop
    }catch(InputMismatchException e){
        System.out.println("incorrect input! \n");
        System.out.println("Please enter the second date \n");
    }
}

with a sentinel as control flow (not the case with Scanner but provided for future reference)

while((y1=scanner.nextInt())!=-1){
    System.out.println("incorrect input! \n");
    System.out.println("Please enter the second date \n");
}