How to check values in a string?

Question

So i have a string in military time format : "1532" corresponding to 3:32pm. I'm trying to write a method to check if each digit in time string is an appropriate digit. So the first element cannot be greater than 2 or equal to 0, and so forth. Currently, my code doesn't run past the second log statement and I'm hoping you guys could help!

cheers!

String mOpen =  "1532";                
Log.d("hoursTesting","pass1, length is > 2");
if(mOpen.getText().length() == 4)
{
    Log.d("hoursTesting","pass2, length is == 4");
    char[] tempString = mOpen.getText().toString().toCharArray();
    if(tempString[0] != 0 && tempString[0] < 3)
    {
        Log.d("hoursTesting","pass3, first index is != 0 and < 3");
        if(tempString[0] == 1)
        {
            Log.d("hoursTesting","pass4, first index is 1");
            if(tempString[2] <= 5)
            {
                Log.d("hoursTesting","pass5, third index is <= 5, success!");
            }
       }
       else   //tempString[0] is equal to 2
       {
            Log.d("hoursTesting","pass4, first index is 2");
            if(tempString[1] < 4)
            {
                 Log.d("hoursTesting","pass5, second index is <3");
                 if(tempString[2] <= 5)
                 {
                     Log.d("hoursTesting","pass6, third index is <= 5, success!");
                 }
            }
        }
   }

}

Have you tried debugging? It will probably be obvious if you can visually see what is happening at each step. — jrmullen
– jrmullen, Commented Nov 17, 2016 at 1:14

John3136 · Accepted Answer · 2016-11-17 01:19:12Z

3

tempString contains characters, not numbers. i.e. '0' not 0 etc.

Easiest fix is to compare characters e.g. tempString[0] == '1' Alternatively, you can do something like int digit1 = tempString[0] - '0'; - but that kind of assumes you already know you just have digits in the string.

Note that cos of those clever ASCII guys and their tricky character set '0' < '1' < '2' etc, so you can still say if (str[0] < '2') etc. You just need to be a bit careful that you are only dealing with digits.

Personally I'd convert the first 2 chars to a number and the second 2 chars to a number and then just check 0 <= number1 <= 23 and 0 <= number2 <= 59.

edited Nov 17, 2016 at 1:19

answered Nov 17, 2016 at 1:14

John3136

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2 Comments

TheQ Over a year ago

yeah i have digits in the string, thanks ill try that out.

TheQ Over a year ago

but what about if i want to check if the char is less than equal to the value?

Sergei Sirik · Accepted Answer · 2016-11-17 01:19:14Z

1

You are comparing char with int here:

if(tempString[0] != 0 && tempString[0] < 3)

It should work like this:

if(tempString[0] != '0' && tempString[0] < '3')

answered Nov 17, 2016 at 1:19

Sergei Sirik

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Comments

Tim Biegeleisen · Accepted Answer · 2016-11-17 01:20:22Z

1

I would substring the hours and minutes components and then check to see if each one be in range:

public boolean isTimeValid(String mOpen) {
    int hours = Integer.parseInt(mOpen.substring(0, 2));
    int minutes = Integer.parseInt(mOpen.substring(2));

    if ((hours >= 0 && hours <= 24) && (minutes >= 0 && minutes <= 59)) {
        return true;
    }
    else {
        return false;
    }
}

answered Nov 17, 2016 at 1:20

Tim Biegeleisen

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