public class Main {

    public static void main(String... args) {
        String word = "при_+вет";
        String str = "";

        if (!word.matches("[^А-Яа-я0-9]+$")) {
            str = "Слово не найдено";
        }

        System.out.println(str);
    }

}

Слово не найдено

public class Main {

    public static void main(String... args) {
        String message = "Hello " + "world.";

        System.out.println(message);
    }

}

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

public class Main {
    private static String word;

    public static void main(String... args) {
        Main main = new Main();

        word = null;
        System.out.println(main.toString());
        word = "";
        System.out.println(main.toString());
        word = "ab";
        System.out.println(main.toString());

        word = "A!";
        System.out.println(main.toString());

        word = "Applet";
        System.out.println(main.toString());

        word = "Apple";
        System.out.println(main.toString());
    }

    private final Pattern TITLE = Pattern.compile("\\<title\\>(.*)\\<\\/title\\>");

    public String search(String url, String someword) {

        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(new URL(url).openStream(), "UTF-8"));
            StringBuilder input = new StringBuilder();
            String line;
            while ((line = in.readLine()) != null) {
                input.append(line);
            }
            if (Pattern.compile(someword, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE).matcher(input).find()) {
                Matcher title = TITLE.matcher(input);
                if (title.find()) {
                    return title.group(1);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (PatternSyntaxException e) {
            e.printStackTrace();
        }
        return null;
    }

    public String toString() {
        String[] argi = {"http://apple.com"};
        String str = "";

        for (int i = 0; i < argi.length; i++) {
            String result = search(argi[i], "\\b" + word + "\\b");

            if (word == null || word.isEmpty()) {
                str = "Enter a search word!";
            } else if (!word.matches("^\\w+$") || word.length() < 3) {
                str = "Word not found!";
            } else if (result != null && word.length() > 2) {
                str += "Search phrase " + "<b>" + word + "</b>" + " have found in " + "<a href=\"" + argi[i] + "\">" + result + "</a>" + "<p></p>";
            }
        }

        return "For word `" + word + "`: " + str;
    }

}

For word `null`: Enter a search word!
For word ``: Enter a search word!
For word `ab`: Word not found!
For word `A!`: Word not found!
For word `Applet`: 
For word `Apple`: Search phrase <b>Apple</b> have found in <a href="http://apple.com">Apple</a><p></p>