嗨,我现在是java的新手。我有一个工作代码,但如果用户输入时间错误,我希望它回到开头。我似乎无法解决这个问题,有一种简单的方法可以做到。
package Time_calculation;
import java.util.*;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Time_calculation {
public static void main(String[] args) {
SimpleDateFormat timeFormat = new SimpleDateFormat ("HH:mm:ss");
Date T1 = null;
Date T2 = null;
Scanner RFK = new Scanner(System.in);
boolean programrunning = true;
while (programrunning == true){
System.out.println("Enter start time HH:MM: (If you wish to exit please type 'Exit')");
String srtTime = RFK.nextLine();
if (srtTime .matches ("Exit")){
System.out.println("Exiting...");
System.exit(0);
}else{
try{
T1 = timeFormat.parse(srtTime);
}catch (Exception e){
System.err.println("Error");}
System.out.println("Enter end time HH:MM:SS (If you wish to exit please type 'Exit')");
String endtime = RFK.nextLine();
if (endtime .matches ("Exit")){
System.out.println("Exiting...");
System.exit(0);
}else{
try{
T2 =timeFormat.parse(endtime);
}catch (Exception e){
System.err.println("Error");}
long diff = T2.getTime() - T1.getTime();
long diffsec = diff / 1000;
System.out.println("Your time in seconds is: " + diffsec + " seconds");
double ms = 1609.344 / diffsec;
double mph = ms * 2.23693629;
System.out.println("Speed in M/S: " + ms);
System.out.println("Speed in MPH is: " + mph);
if(mph > 6){
System.out.println("Running faster than average speed!");}
else{
System.out.println("You are running lower than average speed!");}
System.out.println();
}
}
}
}
}
有没有人有任何想法,它会真的有帮助。
答案 0 :(得分:0)
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;
public class TimeCalculation {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
while (true) {
Date start = TimeCalculation
.readInput(
"Enter start time HH:MM: (If you wish to exit please type 'Exit')",
sc);
Date end = TimeCalculation
.readInput(
"Enter End time HH:MM: (If you wish to exit please type 'Exit')",
sc);
// Do whatever you want with start and end here
}
}
/*
* Take care of reading input if valid input found return it else propmt again for valid input or exit if user wants
* */
public static Date readInput(String msg, Scanner sc) {
Date output = null;
boolean isValid = false;
SimpleDateFormat timeFormat = new SimpleDateFormat("HH:mm:ss");
while (!isValid) {
System.out.println(msg);
String time = sc.nextLine();
if (time.matches("Exit")) {
System.out.println("Exiting...");
System.exit(0);
} else {
try {
output = timeFormat.parse(time);
isValid = true;
} catch (Exception e) {
System.out.println("Invalid Input");
}
}
}
return output;
}
}