pattern.matcher() vs pattern.matches()

Question

I am wondering why the results of the java regex pattern.matcher() and pattern.matches() differ when provided the same regular expression and same string

Answer 1

Pattern.matches is testing the whole String, in your case you should use:

 System.out.println(java.util.regex.Pattern.matches(".*\\+", str));

Meaning any string and a + symbol

Answer 2

From the Javadoc, see the if, and only if, the entire region section

   /**
     * Attempts to match the entire region against the pattern.
     *
     * <p> If the match succeeds then more information can be obtained via the
     * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
     *
     * @return  <tt>true</tt> if, and only if, <b>the entire region</b> sequence
     *          matches this matcher's pattern
     */
    public boolean matches() {
        return match(from, ENDANCHOR);
    }

So if your String was just "+", you'd get a true result.