How to Limit the String values in java

Question

I am Extracting the month From this String by using Substring.

String main="2014-07-30 13:30:00";
String month=main.substring(5, 7);

Bt now i wanted to limit the month i.e.

if(month<0 || month>12)
{
sysout("Wrong Input");
}

So what Shoud i Do???

Use a `DateTimeFormatter` and use `parse` to validate your input — Robin Topper, May 08 '17 at 07:40

score 0 · Answer 1 · answered May 08 '17 at 08:12

0

public static void main(String[] args) {
    String main="2014-11-30 13:30:00";
    String pattern = "yyyy-MM-dd HH:mm:ss";
    DateFormat formatter = new SimpleDateFormat(pattern);
    try {
        Date date = formatter.parse(main);
        if(!main.equals(formatter.format(date)))
            System.out.println("Wrong input");
    } catch (ParseException e) {
        System.out.println("Wrong input");
    }
}

answered May 08 '17 at 08:12

dung ta van

988
8
13

FYI, the troublesome old date-time classes such as [`java.util.Date`](https://docs.oracle.com/javase/8/docs/api/java/util/Date.html), [`java.util.Calendar`](https://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html), and `java.text.SimpleTextFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [java.time](https://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html) classes. See [Tutorial by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). – Basil Bourque May 08 '17 at 09:28

score 0 · Accepted Answer · edited May 23 '17 at 12:17

Using java.time

The modern approach is with the java.time classes.

Parse the string as a date-time object, a LocalDateTime in this particular case. If the parsing fails, you know the input was wrong.

To parse, alter your input to fully comply with the ISO 8601 standard. This means replacing that SPACE in the middle with a T. The java.time classes use the standard formats by default when parsing/generating strings. So no need to specify a formatting pattern.

String input = "2014-07-30 13:30:00".replace( " " , "T" );

Catch the exception thrown if the input is faulty such as the month number being out of the range of 1-12.

try {
    LocalDateTime ldt = LocalDateTime.parse( input );
} catch (DateTimeParseException e ) {
    // Handle this error, when we receive faulty input.
    System.out.println( "Wrong input." ); 
}

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

Java SE 8, Java SE 9, and later
- Built-in.
- Part of the standard Java API with a bundled implementation.
- Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
- Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
- The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
- See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

How to Limit the String values in java

2 Answers2

Using java.time

About java.time