Format a message using MessageFormat.format() in Java

You need to use double apostrophe instead of single in the "You''re", eg:

String text = java.text.MessageFormat.format("You''re about to delete {0} rows.", 5);
System.out.println(text);

Just be sure you have used double apostrophe ('')

String text = java.text.MessageFormat.format("You''re about to delete {0} rows.", 5);
System.out.println(text);

Edit:

Within a String, a pair of single quotes can be used to quote any arbitrary characters except single quotes. For example, pattern string "'{0}'" represents string "{0}", not a FormatElement. ...

Any unmatched quote is treated as closed at the end of the given pattern. For example, pattern string "'{0}" is treated as pattern "'{0}'".

Source http://docs.oracle.com/javase/7/docs/api/java/text/MessageFormat.html

Add an extra apostrophe ' to the MessageFormat pattern String to ensure the ' character is displayed

String text = 
     java.text.MessageFormat.format("You''re about to delete {0} rows.", 5);
                                         ^

An apostrophe (aka single quote) in a MessageFormat pattern starts a quoted string and is not interpreted on its own. From the javadoc

A single quote itself must be represented by doubled single quotes '' throughout a String.

The String You\\'re is equivalent to adding a backslash character to the String so the only difference will be that You\re will be produced rather than Youre. (before double quote solution '' applied)