java need to match * with any character

Question

I am new to Java so spare me. Below you can see my code. What it should do is read the 3th column from text file and if this column is S**ei or P***ei it returns the first word in that line. However my question is "How can I make * match any character from a to z"?. I heard of regular expressions but haven't really worked with them yet. Any help would be much appreciated. Thanks.

package test;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class moja {
    public static void main(String[] args) {
        try {
            File file = new File("SloveneLexicon.txt");
            FileReader fileReader = new FileReader(file);
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            StringBuffer stringBuffer = new StringBuffer();
            String vrstica;
            while ((vrstica = bufferedReader.readLine()) != null) {

                String s = vrstica;
                String[] dobi_besedo_v_vrstici = s.split("\\s+");
                String prva_beseda = dobi_besedo_v_vrstici[0];
                String tretja_beseda = dobi_besedo_v_vrstici[2];
                if (tretja_beseda =="S**ei"){
                    System.out.println(prva_beseda);
                    if (tretja_beseda =="P***ei")
                        System.out.println(prva_beseda);
                }

            }
            bufferedReader.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Please read How do I compare strings in Java? (Hint equals rather than ==) — reto
– reto, Commented Oct 22, 2014 at 7:44
Why the hell was this closed as duplicate? It's not about string comparison, it's about regex matching a string. — Pimgd
– Pimgd, Commented Oct 22, 2014 at 7:46
Indeed. The string comparison issue was just a minor problem. To Rok Ivartnik: Regular expressions tutorial — RealSkeptic
– RealSkeptic, Commented Oct 22, 2014 at 7:47

Beri · Accepted Answer · 2014-10-22 07:52:02Z

1

    Pattern p = Pattern.compile("Pi[a-zA-z]{3}ei");
    if(p.matcher(input).matches()){
        This will work for 3 any letters (big or small)
    }

"Pi[a-zA-z]{3}ei" // 3 letters big or small
"Pi[a-zA-z]{1,3}ei" // 1-3 letters big or small
"Pi[a-zA-z]+ei" // at least one letter
"Pi[a-zA-z]*ei" // zero or more letters

Just remember to put your Pattern outside while loop, you should define it once and use many times

answered Oct 22, 2014 at 7:52

Beri

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1 Comment

Beri Over a year ago

Glad I could help:) Good luck in improving your skills:)

Margus · Accepted Answer · 2014-10-22 07:46:59Z

1

Take a look at regex pattern matcher :

manual : http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

Example :

 Pattern p = Pattern.compile("a*b");
 Matcher m = p.matcher("aaaaab");
 boolean b = m.matches();

answered Oct 22, 2014 at 7:46

Margus

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1 Comment

Ken Y-N Over a year ago

The original problem statement seems to be "HOW CAN I MAKE * MATCHING any character from a - z", so their "S**ei" would be matched with "S[a-z]{2}ei".

steffen · Accepted Answer · 2014-10-22 08:00:23Z

0

Use a pattern matcher (e. g. String.matches()):

    if (tretja_beseda.matches("S[a-zA-Z][a-zA-Z]ei")) {
        System.out.println(prva_beseda);
    }
    if (tretja_beseda == "P[a-zA-Z][a-zA-Z]ei") {
        System.out.println(prva_beseda);
    }

[a-zA-Z] matches any character from a-z (case insensitive). I'm reading SloveneLexicon.txt in your code so I guess you'll also have to deal with slovenian characters (like Č). I'd suggest you to use \\p{L} (matching one unicode letter) instead of [a-zA-Z]:

    if (tretja_beseda.matches("S\\p{L}\\p{L}ei")) {
        System.out.println(prva_beseda);
    }

Second, your if-logic can not work since you nested the second if inside the first, but both conditions can't be true at the same time (String starting with S and P).

Third, I'd suggest you to program in english so you don't mix languages in your code making it easier to read; but that's of course up to you.

answered Oct 22, 2014 at 8:00

steffen

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5 Comments

Rok Ivartnik Over a year ago

č is not a problem since there are no č,š,ž in treja_beseda

Rok Ivartnik Over a year ago

and how can mine if be both true at the same time since i am reading 1 line and only Pei or S*ei can accour once in every line

steffen Over a year ago

The second if is only evaluated if the first if was true. Your code: if (cond1) { code1(); if (cond2) { code2; } }. Compare this: if (cond1) { code1(); } if (cond2) { code2(); }

Rok Ivartnik Over a year ago

hello if you can help me if (tretja_beseda.matches("S\\p{L}\\p{L}ei")) what would i have to put behind ei to have 0 or infinite word possible icludint š,č. Is this ok? (tretja_beseda.matches("S\\p{L}\\p{L}ei\\p{L}*"))

steffen Over a year ago

@RokIvartnik Yes, that would match all letters after ei (0..∞ times).

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