I can have these three kind of Strings

```
ALPHA_whatever_1234567

BETA_whateverDifferent_7654321

GAMMA_anotherOption_1237654

```

I want to extract from the Strings the beginning of them, whether is ALPHA, BETA or GAMMA.

So, for example, I would like to get:

```
ALPHA_whatever_1234567 -> ALPHA

BETA_whateverDifferent_7654321 -> BETA

GAMMA_anotherOption_1237654 -> GAMMA

```

I want to use Regular Expression, and I tried something like this

```
private static final Pattern PATTERN = Pattern.compile("(.*)_.*");

```

But it doesn't work for some Strings. I recover the beginning by 

```
Matcher m = PATTERN.matcher(string);
m.find(1);

```

I also tried this Pattern:

```
private static final Pattern PATTERN = Pattern.compile("([ALPHA]|[BETA]|[GAMMA])_.*");

```

But it returns only the first character of the String.

What am I doing wrong?