[SOLVED] how to run loop unless and until user enter correct value

[mfaizan24]

Hello everyone,
I'm trying write such which ask user again to enter correct value if user enter wrong one.

like I'm using this code..

import java.io.*;
import java.util.*;
public class test {

public static void main(String[] args) {

boolean t = true;
String g;
int age;
Scanner s = new Scanner(System.in);
do{
System.out.println("Enter gender: m/f");
g = s.next();
System.out.println("Enter age");
age = s.nextInt();

System.out.println("Continue....true/false");
t=s.nextBoolean();

}while(t);
}
}


if user instead of enter m or f or male or female he enter something else like
'k' or anything else the loop goes back and ask user to enter correct value
how can I do this...
please any suggestion

[Supamagier]

do{
do{
System.out.println("Enter gender: m/f");
g = s.next();
while (!g.equalsIgnoreCase("m") && !g.equalsIgnoreCase("f"));
System.out.println("Enter age");
age = s.nextInt();

System.out.println("Continue....true/false");
t=s.nextBoolean();

}while(t);

I assume you now can, using this example, do the loop for the age aswell (e.g. negative or absurd low/high age)

[RamyaSivakanth]

Hi
go thru this below link

Java Programming Notes

[mfaizan24]

Hi Supamagier,
This code is not working, I've change && to || but nothing happening.
Hi Ramyasivakanth,
Thanks for such informative notes but I didn't any suitable information for me.
please help me out in this I've completed almost eveything just stuck in this section.

[mfaizan24]

Hi Supamagier,
This code is not working, I've change && to || but nothing happening.
Hi Ramyasivakanth,
Thanks for such informative notes but I didn't any suitable information for me but they are really informative thanks again for such amazing notes.

please help me out in this I've completed almost eveything just stuck in this section.

[CJSLMAN]

mfaizan24: just stating that the code isn't working, doesn't help in understanding the problem you're having. Please post your code (with Supamagier's suggested changes) and explain what the problem you're having with this code.

Luck,
CJSL

[angryboy]

using a helper method would make this more clear.

// pseudo code:
ask for input

while input != m or f
  print error, ask for input.
  repeat this loop.

return input

[mfaizan24]

import java.io.*;
import java.util.*;
public class test {

public static void main(String[] args)throws Exception {

boolean t = true;
String g="";
int age;

Scanner s = new Scanner(System.in);

do{

System.out.println("Enter gender: m/f");
g = s.next();
while (!g.equalsIgnoreCase("m") || !g.equalsIgnoreCase("f"));

System.out.println("Enter age");
age = s.nextInt();

System.out.println("Continue....true/false");
t=s.nextBoolean();

}while(t);
}
}

here's my complete codes

[angryboy]

does it do what you wanted?

also this is shorter:

while (!g.matches("^[mMfF]$"))
          continue;

[mfaizan24]

No it doesn't do what I want, All I want this loop should continue unless and until user enter the correct value
eg.
Enter gender m/f
k
// if user here press something like k or l instead of m/f it should go back and ask user again to enter correct value.

but above posted codes are working but screen goes stuck.

[mfaizan24]

Hi,
I've change while to if statement and its working perfectly fine

public static void main(String[] args) {
String g;
int age;
boolean t=true;
Scanner sc = new Scanner(System.in);

do{
System.out.println("enter gender");
g = sc.next();
if(!g.matches("^[mMfF]$")){
continue;
}

System.out.println("Enter age");
age = sc.nextInt();
if(age < 0){
continue;
}

System.out.println("continue!!....true/false");
t = sc.nextBoolean();
}while(t);

but stuck in age

}

[Supamagier]

if(!g.matches("^[mMfF]$"))

You shouldn't use code you don't understand (I don't think you do tbh)

[mfaizan24]

How can I apply this codes for age..

System.out.println("Enter age");
age = sc.nextInt();
if(age < 0){
continue;
}

it doesn't work..

[angryboy]

what's not working?

S:\>java Test
enter gender
m
Enter age
0
continue!!....true/false
false
END

S:\>java Test
enter gender
m
Enter age
-2
enter gender
m
Enter age
1000
continue!!....true/false
false
END

[mfaizan24]

m
Enter age
-2 //Here I'm stuck
enter gender
m
Enter age
1000
continue!!....true/false
false
END

=============

It shouldn't go back to gender it should stay at age only
like if user enter 0 or -2
it should ask user to enter age
not enter gender

but this loop is going back to gender which is already checked.
Please help me out...

[angryboy]

that cause you changed while to an if

     while(!g.matches("^[mMfF]$")){
   [B]     g = sc.next(); // Dop! update user input[/B]
        //continue; 
      }

You want:
While Not M or F, loop
While Age < 0, loop
If True, Then continue
Else End.

[CJSLMAN]

A couple of comments/suggestions...
Maybe two "while" loops are needed for this cases (I'm pretty sure that one can be used, but it would probably confuse the OP)

[LIST][*]genderOK = false [*]start while loop (!genderOK)[*]ask for gender[*]compare if gender is correct[*]if yes, genderOK = true[*]end while loop[/LIST]

And then do the same (another loop) for the age verification.

Now to do it all in one loop...

[LIST][*]genderOK = false[*]ageOK = false[*]start while loop (!genderOK && !ageOK) [*]if genderOK == false[*]{[*]ask for gender[*]compare if gender is correct[*]if yes, genderOK = true[*]}[*]ask for age[*]compare if age is correct[*]if yes, ageOK = true[*]end while loop[/LIST]

.... or something close to that (check the "||" logic... it might be "&&").

Luck,
CJSL

[angryboy]

for the one loop pseudo code, put in a "continue;" inside the if statement. and use &&.

[mfaizan24]

I am sorry I really didn't understand anything..

[CJSLMAN]

Here are some links you have to study to understand:

• The while and do-while Statements (The Java™ Tutorials > Learning the Java Language > Language Basics)
• The for Statement (The Java™ Tutorials > Learning the Java Language > Language Basics)
• The if-then and if-then-else Statements (The Java™ Tutorials > Learning the Java Language > Language Basics)
• Equality, Relational, and Conditional Operators (The Java™ Tutorials > Learning the Java Language > Language Basics)
• Java: Boolean

Luck,
CJSL