CODEWITHSUNDEEP
javaregex
Taylor Kems
Taylor Kems

Reputation: 337

Android regex always returning false

I am having issues with regex always returning false even though "http://developer.android.com/reference/java/util/regex/Pattern.html" states it shouldn't.

I am entering all kinds of specials charaters "&$@R@," and b/b2 are both returning false in the logcat. The string I am putting into the edit text even displays in logcat as the exact one I input. Anyone have an idea as to why it won't match the alphanumeric characters?

Code:

    EditText et1 = (EditText) findViewById(R.id.editText1);
    String et1Text = et1.getText().toString();
    int et1Length = et1.getText().toString().length();
    EditText et2 = (EditText) findViewById(R.id.editText2);
    String et2Text = et2.getText().toString();
    int et2Length = et2.getText().toString().length();

    Pattern p = Pattern.compile("\\W");
    Log.d(TAG,et1Text);
    Matcher m = p.matcher(et1Text);
    boolean b = m.matches();
    if (b == true){
        Log.d(TAG,"True");
    }
    else {
        Log.d(TAG,"False");
    }
    Log.d(TAG,et2Text);
    Matcher m2 = p.matcher(et2Text);
    boolean b2 = m2.matches();
    if (b2 == true){
        Log.d(TAG,"True");
    }
    else {
        Log.d(TAG,"False");
    }

    if (et1Length < 4 | et1Length > 15 | et2Length < 4 | et2Length > 15){
        Log.d(TAG,"Length dialog");
        dialog(1);
    }

    if (b==true | b2==true){
        Log.d(TAG,"Special char dialog");
        dialog(1);
    }

Upvotes: 2

Views: 1684

Answers (6)

Kurtis Nusbaum
Kurtis Nusbaum

Reputation: 30825

If you want a regular express that matches all alphanumeric characters try [a-zA-Z0-9]*. If you want to match all non alphanumeric characters in a string try this \\W*

Upvotes: 0

Alan Moore
Alan Moore

Reputation: 75242

\W (or as a java string literal, "\\W") matches one non-word character. The matches() method implicitly anchors the match at both ends, as if you had really written "\\A\\W\\z". So you'll only get a match if the string consists of exactly one non-word character. If you want to match one or more characters, you should change the regex to 

"\\W+"

Upvotes: 0

Lycha
Lycha

Reputation: 10177

Instead of matches() which tries to match the whole string to pattern you can use find() which just tries to find any occurrence of the pattern. Source

Upvotes: 2

FailedDev
FailedDev

Reputation: 26930

I have no idea about android but this regex : 

Pattern p = Pattern.compile("\\W");

Will match any non alphanumeric character. If you would expand it, it would look like this : 

[^a-zA-Z0-9_]

If you want to match a single alphanumeric character including _ just use : 

Pattern p = Pattern.compile("\\w");

else use : Pattern p = Pattern.compile("[a-zA-Z0-9]");

Upvotes: 0

Marcus
Marcus

Reputation: 12586

First of all an uppercase W matches any non-alphanumeric character. Secondly you only matches one single character. To match that the string only contains alphanumerical characters use the following regex:

String pattern = "[\\w]*";

Note that \w also matches underscore.

Upvotes: 2

aleph_null
aleph_null

Reputation: 5786

The Matcher method, "matches", tries to match the Pattern against the entire region. The regular expression "\W" matches a SINGLE non-alphanumeric character. In other words, m.matches() will return true when you attempt to match it to a SINGLE special character. If you attempt to match it to "&$@R@,", it will return false since the string contains more than just a single non-alphanumeric character.

Upvotes: 0

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