Why Does DateFormat Throw a \'Cannot Format Given Object as a Date\' Exception?

DateFormat Cannot Format String Objects

In Java, the DateFormat class is designed specifically to format and parse Date objects, not strings. The provided code demonstrates a common error where a string representation of a date ("2012-11-17T00:00:00.000-05:00") is directly passed to the DateFormat.format() method. This results in the "Cannot format given Object as a Date" exception.

Two SimpleDateFormat Objects Approach

To resolve this issue, it's necessary to utilize two SimpleDateFormat objects: one for parsing the string into a Date object and another for formatting the Date object in the desired format. The following revised code addresses the issue:

<code class="java">import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;

public class DateParser {    
  public static void main(String args[]) {   
    String MonthYear = null;    
    String dateformat = "2012-11-17T00:00:00.000-05:00";

    SimpleDateFormat inputFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSX", Locale.US);
    SimpleDateFormat outputFormat = new SimpleDateFormat("MM/yyyy", Locale.US);

    try {
      Date date = inputFormat.parse(dateformat);
      MonthYear = outputFormat.format(date);    
      System.out.println(MonthYear);    
    } catch (ParseException e) {
      System.err.println("Invalid date format.");
    }
  }    
}</code>

In this code:

• inputFormat is used to parse the input string into a Date object.
• outputFormat is then used to format the Date object in the desired "mm/yyyy" format.
• The code handles potential ParseException exceptions when parsing the input string.

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