问题
Here is an example:
public MyDate() throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/d");
sdf.setLenient(false);
String t1 = "2011/12/12aaa";
System.out.println(sdf.parse(t1));
}
2011/12/12aaa is not a valid date string. However the function prints "Mon Dec 12 00:00:00 PST 2011" and ParseException isn't thrown.
Can anyone tell me how to let SimpleDateFormat treat "2011/12/12aaa" as an invalid date string and throw an exception?
回答1:
The JavaDoc on parse(...)
states the following:
parsing does not necessarily use all characters up to the end of the string
It seems like you can't make SimpleDateFormat
throw an exception, but you can do the following:
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/d");
sdf.setLenient(false);
ParsePosition p = new ParsePosition( 0 );
String t1 = "2011/12/12aaa";
System.out.println(sdf.parse(t1,p));
if(p.getIndex() < t1.length()) {
throw new ParseException( t1, p.getIndex() );
}
Basically, you check whether the parse consumed the entire string and if not you have invalid input.
回答2:
To chack whether a date is valid The following method returns if the date is in valid otherwise it will return false.
public boolean isValidDate(String date) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/d");
Date testDate = null;
try {
testDate = sdf.parse(date);
}
catch (ParseException e) {
return false;
}
if (!sdf.format(testDate).equals(date)) {
return false;
}
return true;
}
Have a look on the following class which can check whether the date is valid or not
** Sample Example**
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateValidCheck {
public static void main(String[] args) {
if(new DateValidCheck().isValidDate("2011/12/12aaa")){
System.out.println("...date is valid");
}else{
System.out.println("...date is invalid...");
}
}
public boolean isValidDate(String date) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/d");
Date testDate = null;
try {
testDate = sdf.parse(date);
}
catch (ParseException e) {
return false;
}
if (!sdf.format(testDate).equals(date)) {
return false;
}
return true;
}
}
回答3:
After it successfully parsed the entire pattern string SimpleDateFormat
stops evaluating the data it was given to parse.
回答4:
Java 8 LocalDate may be used:
public static boolean isDate(String date) {
try {
LocalDate.parse(date, DateTimeFormatter.ofPattern("yyyy/MM/dd"));
return true;
} catch (DateTimeParseException e) {
return false;
}
}
If input argument is "2011/12/12aaaaaaaaa"
, output is false
;
If input argument is "2011/12/12"
, output is true
回答5:
Take a look on the method documentation which says: ParseException if the beginning of the specified string cannot be parsed
.
Method source code with javadoc:
/**
* Parses text from the beginning of the given string to produce a date.
* The method may not use the entire text of the given string.
* <p>
* See the {@link #parse(String, ParsePosition)} method for more information
* on date parsing.
*
* @param source A <code>String</code> whose beginning should be parsed.
* @return A <code>Date</code> parsed from the string.
* @exception ParseException if the beginning of the specified string
* cannot be parsed.
*/
public Date parse(String source) throws ParseException
{
ParsePosition pos = new ParsePosition(0);
Date result = parse(source, pos);
if (pos.index == 0)
throw new ParseException("Unparseable date: \"" + source + "\"" ,
pos.errorIndex);
return result;
}
回答6:
You can use the ParsePosition
class or the sdf.setLenient(false)
function
Docs: http://docs.oracle.com/javase/7/docs/api/java/text/ParsePosition.html http://docs.oracle.com/javase/7/docs/api/java/text/DateFormat.html#setLenient(boolean)
回答7:
Simply setting sdf.setLenient(false)
will do the trick..
来源:https://stackoverflow.com/questions/8428313/simpledateformat-parsestring-str-doesnt-throw-an-exception-when-str-2011-12