Android Java Zeichenkettenverarbeitungsbeispiele

// Android Java String Split and Join Examples
// Java standard library string operations

import java.util.*;
import java.util.stream.Collectors;

// 1. Basic String Splitting
class StringSplitter {

    // Split by single delimiter
    public String[] splitByDelimiter(String text, String delimiter) {
        return text.split(delimiter);
    }

    // Split by multiple delimiters
    public String[] splitByMultipleDelimiters(String text, String[] delimiters) {
        String result = text;
        for (String delimiter : delimiters) {
            result = result.replace(delimiter, " ");
        }
        return result.trim().split("\\s+");
    }

    // Split by regex pattern
    public String[] splitByRegex(String text, String pattern) {
        return text.split(pattern);
    }

    // Split with limit
    public String[] splitWithLimit(String text, String delimiter, int limit) {
        return text.split(delimiter, limit);
    }

    // Split into lines
    public String[] splitIntoLines(String text) {
        return text.split("\\r?\\n");
    }

    // Split by whitespace
    public String[] splitByWhitespace(String text) {
        return text.trim().split("\\s+");
    }

    // Split and trim
    public String[] splitAndTrim(String text, String delimiter) {
        String[] parts = text.split(delimiter);
        List<String> result = new ArrayList<>();
        for (String part : parts) {
            String trimmed = part.trim();
            if (!trimmed.isEmpty()) {
                result.add(trimmed);
            }
        }
        return result.toArray(new String[0]);
    }
}

// 2. String Joining
class StringJoiner {

    // Join with delimiter
    public String joinWithDelimiter(String[] parts, String delimiter) {
        return String.join(delimiter, parts);
    }

    // Join list with delimiter
    public String joinList(List<String> parts, String delimiter) {
        return String.join(delimiter, parts);
    }

    // Join with prefix and suffix using StringJoiner
    public String joinWithPrefixSuffix(String[] parts, String delimiter, String prefix, String suffix) {
        StringJoiner joiner = new StringJoiner(delimiter, prefix, suffix);
        for (String part : parts) {
            joiner.add(part);
        }
        return joiner.toString();
    }

    // Join with transformation
    public String joinWithTransform(List<Integer> numbers, String delimiter) {
        return numbers.stream()
            .map(String::valueOf)
            .collect(Collectors.joining(delimiter));
    }

    // Join non-null elements
    public String joinNonNull(List<String> parts, String delimiter) {
        List<String> nonNull = new ArrayList<>();
        for (String part : parts) {
            if (part != null) {
                nonNull.add(part);
            }
        }
        return String.join(delimiter, nonNull);
    }

    // Join lines
    public String joinLines(String[] lines) {
        return String.join("\\n", lines);
    }

    // Join with index
    public String joinWithIndex(String[] parts, String delimiter) {
        List<String> withIndex = new ArrayList<>();
        for (int i = 0; i < parts.length; i++) {
            withIndex.add(i + ": " + parts[i]);
        }
        return String.join(delimiter, withIndex);
    }
}

// 3. Advanced String Operations
class AdvancedStringOperations {

    // Parse CSV line
    public String[] parseCSVLine(String line) {
        String[] parts = line.split(",");
        String[] result = new String[parts.length];
        for (int i = 0; i < parts.length; i++) {
            result[i] = parts[i].trim();
        }
        return result;
    }

    // Parse key-value pairs
    public Map<String, String> parseKeyValuePairs(String text, String pairDelimiter, String kvDelimiter) {
        Map<String, String> result = new HashMap<>();
        String[] pairs = text.split(pairDelimiter);

        for (String pair : pairs) {
            String[] parts = pair.split(kvDelimiter, 2);
            if (parts.length == 2) {
                result.put(parts[0].trim(), parts[1].trim());
            }
        }

        return result;
    }

    // Word wrap
    public String[] wordWrap(String text, int maxWidth) {
        String[] words = text.split("\\s+");
        List<String> lines = new ArrayList<>();
        StringBuilder currentLine = new StringBuilder();

        for (String word : words) {
            String testLine = currentLine.length() == 0 ? word : currentLine + " " + word;
            if (testLine.length() <= maxWidth) {
                currentLine = new StringBuilder(testLine);
            } else {
                if (currentLine.length() > 0) {
                    lines.add(currentLine.toString());
                }
                currentLine = new StringBuilder(word);
            }
        }

        if (currentLine.length() > 0) {
            lines.add(currentLine.toString());
        }

        return lines.toArray(new String[0]);
    }

    // Capitalize first letter
    public String capitalize(String text) {
        if (text == null || text.isEmpty()) {
            return text;
        }
        return Character.toUpperCase(text.charAt(0)) + text.substring(1);
    }

    // Capitalize all words
    public String capitalizeWords(String text) {
        String[] words = text.split("\\s+");
        StringBuilder result = new StringBuilder();

        for (int i = 0; i < words.length; i++) {
            if (i > 0) {
                result.append(" ");
            }
            if (!words[i].isEmpty()) {
                result.append(Character.toUpperCase(words[i].charAt(0)));
                if (words[i].length() > 1) {
                    result.append(words[i].substring(1).toLowerCase());
                }
            }
        }

        return result.toString();
    }

    // Reverse string
    public String reverse(String text) {
        return new StringBuilder(text).reverse().toString();
    }

    // Count occurrences
    public int countOccurrences(String text, String substring) {
        int count = 0;
        int index = 0;

        while ((index = text.indexOf(substring, index)) != -1) {
            count++;
            index += substring.length();
        }

        return count;
    }
}

// 4. String Builder for Efficient Building
class EfficientStringBuilder {

    // Build string with StringBuilder
    public String buildStringEfficiently(String[] parts) {
        StringBuilder sb = new StringBuilder();
        for (String part : parts) {
            sb.append(part).append(" ");
        }
        return sb.toString().trim();
    }

    // Build with conditional parts
    public String buildWithConditionals(String base, String optional, boolean includeOptional) {
        StringBuilder sb = new StringBuilder();
        sb.append(base);

        if (includeOptional && optional != null) {
            sb.append(" ").append(optional);
        }

        return sb.toString();
    }

    // Build with loop
    public String buildWithLoop(List<String> items, String separator) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < items.size(); i++) {
            if (i > 0) {
                sb.append(separator);
            }
            sb.append(items.get(i));
        }
        return sb.toString();
    }

    // Build with formatted values
    public String buildWithFormat(String template, Object... args) {
        return String.format(template, args);
    }
}

// 5. String Utilities
class StringUtils {

    // Check if string is empty or null
    public boolean isEmpty(String text) {
        return text == null || text.isEmpty();
    }

    // Check if string is blank (empty or whitespace only)
    public boolean isBlank(String text) {
        return text == null || text.trim().isEmpty();
    }

    // Truncate string
    public String truncate(String text, int maxLength) {
        if (text == null || text.length() <= maxLength) {
            return text;
        }
        return text.substring(0, maxLength);
    }

    // Truncate with suffix
    public String truncateWithSuffix(String text, int maxLength, String suffix) {
        if (text == null || text.length() <= maxLength) {
            return text;
        }
        return text.substring(0, maxLength - suffix.length()) + suffix;
    }

    // Pad left
    public String padLeft(String text, int length, char padChar) {
        if (text.length() >= length) {
            return text;
        }

        StringBuilder sb = new StringBuilder();
        int padLength = length - text.length();

        for (int i = 0; i < padLength; i++) {
            sb.append(padChar);
        }

        sb.append(text);
        return sb.toString();
    }

    // Pad right
    public String padRight(String text, int length, char padChar) {
        if (text.length() >= length) {
            return text;
        }

        StringBuilder sb = new StringBuilder(text);
        int padLength = length - text.length();

        for (int i = 0; i < padLength; i++) {
            sb.append(padChar);
        }

        return sb.toString();
    }

    // Remove leading/trailing characters
    public String strip(String text, char stripChar) {
        int start = 0;
        int end = text.length();

        while (start < end && text.charAt(start) == stripChar) {
            start++;
        }

        while (end > start && text.charAt(end - 1) == stripChar) {
            end--;
        }

        return text.substring(start, end);
    }

    // Center text
    public String center(String text, int width, char padChar) {
        if (text.length() >= width) {
            return text;
        }

        int totalPad = width - text.length();
        int leftPad = totalPad / 2;
        int rightPad = totalPad - leftPad;

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < leftPad; i++) {
            sb.append(padChar);
        }

        sb.append(text);

        for (int i = 0; i < rightPad; i++) {
            sb.append(padChar);
        }

        return sb.toString();
    }
}

// 6. String Comparison
class StringComparison {

    // Compare strings (case-sensitive)
    public boolean equals(String str1, String str2) {
        return Objects.equals(str1, str2);
    }

    // Compare strings (case-insensitive)
    public boolean equalsIgnoreCase(String str1, String str2) {
        return str1 != null && str1.equalsIgnoreCase(str2);
    }

    // Compare strings with natural ordering
    public int compare(String str1, String str2) {
        return str1.compareTo(str2);
    }

    // Find common prefix
    public String commonPrefix(String str1, String str2) {
        int minLength = Math.min(str1.length(), str2.length());
        int i = 0;

        while (i < minLength && str1.charAt(i) == str2.charAt(i)) {
            i++;
        }

        return str1.substring(0, i);
    }

    // Find common suffix
    public String commonSuffix(String str1, String str2) {
        int i = 0;
        int len1 = str1.length();
        int len2 = str2.length();

        while (i < len1 && i < len2 &&
               str1.charAt(len1 - 1 - i) == str2.charAt(len2 - 1 - i)) {
            i++;
        }

        return str1.substring(len1 - i);
    }

    // Calculate Levenshtein distance
    public int levenshteinDistance(String str1, String str2) {
        int m = str1.length();
        int n = str2.length();

        int[][] dp = new int[m + 1][n + 1];

        for (int i = 0; i <= m; i++) {
            dp[i][0] = i;
        }

        for (int j = 0; j <= n; j++) {
            dp[0][j] = j;
        }

        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1];
                } else {
                    dp[i][j] = 1 + Math.min(
                        Math.min(dp[i - 1][j], dp[i][j - 1]),
                        dp[i - 1][j - 1]
                    );
                }
            }
        }

        return dp[m][n];
    }
}

// Main demonstration
class StringSplitJoinDemo {
    public static void demonstrateStringSplitJoin() {
        System.out.println("=== Android Java String Split and Join Examples ===\n");

        StringSplitter splitter = new StringSplitter();

        // 1. Basic split
        System.out.println("--- 1. Basic Split ---");
        String text1 = "apple,banana,orange,grape";
        String[] fruits = splitter.splitByDelimiter(text1, ",");
        System.out.println("Split '" + text1 + "':");
        for (String fruit : fruits) {
            System.out.println("  - " + fruit);
        }

        // 2. Split by multiple delimiters
        System.out.println("\n--- 2. Split by Multiple Delimiters ---");
        String text2 = "apple,banana;orange|grape";
        String[] multiDelim = splitter.splitByMultipleDelimiters(text2, new String[]{",", ";", "|"});
        System.out.println("Split by [,,;,|]:");
        for (String item : multiDelim) {
            System.out.println("  - " + item);
        }

        // 3. Split by regex
        System.out.println("\n--- 3. Split by Regex ---");
        String text3 = "apple123banana456orange";
        String[] regexSplit = splitter.splitByRegex(text3, "\\d+");
        System.out.println("Split by digits:");
        for (String item : regexSplit) {
            System.out.println("  - " + item);
        }

        // 4. Split into lines
        System.out.println("\n--- 4. Split into Lines ---");
        String text4 = "Line 1\\nLine 2\\nLine 3";
        String[] lines = splitter.splitIntoLines(text4);
        System.out.println("Lines:");
        for (String line : lines) {
            System.out.println("  - " + line);
        }

        // 5. Join with delimiter
        System.out.println("\n--- 5. Join with Delimiter ---");
        StringJoiner joiner = new StringJoiner();
        String joined = joiner.joinWithDelimiter(fruits, " | ");
        System.out.println("Joined with ' | ': " + joined);

        // 6. Join with prefix and suffix
        System.out.println("\n--- 6. Join with Prefix/Suffix ---");
        String joinedWithBrackets = joiner.joinWithPrefixSuffix(fruits, ", ", "[", "]");
        System.out.println("Joined with brackets: " + joinedWithBrackets);

        // 7. Parse CSV
        System.out.println("\n--- 7. Parse CSV ---");
        AdvancedStringOperations advanced = new AdvancedStringOperations();
        String csvLine = "John,Doe,30,New York";
        String[] parsedCSV = advanced.parseCSVLine(csvLine);
        System.out.println("Parsed CSV:");
        System.out.println("  Name: " + parsedCSV[0] + " " + parsedCSV[1]);
        System.out.println("  Age: " + parsedCSV[2]);
        System.out.println("  City: " + parsedCSV[3]);

        // 8. Parse key-value pairs
        System.out.println("\n--- 8. Parse Key-Value Pairs ---");
        String kvText = "name=John;age=30;city=NYC";
        Map<String, String> kvPairs = advanced.parseKeyValuePairs(kvText, ";", "=");
        System.out.println("Parsed key-values:");
        for (Map.Entry<String, String> entry : kvPairs.entrySet()) {
            System.out.println("  " + entry.getKey() + ": " + entry.getValue());
        }

        // 9. Word wrap
        System.out.println("\n--- 9. Word Wrap ---");
        String longText = "This is a very long text that needs to be wrapped into multiple lines";
        String[] wrapped = advanced.wordWrap(longText, 20);
        System.out.println("Wrapped text:");
        for (String line : wrapped) {
            System.out.println("  " + line);
        }

        // 10. String utilities
        System.out.println("\n--- 10. String Utilities ---");
        StringUtils utils = new StringUtils();
        System.out.println("Capitalize: " + advanced.capitalize("hello"));
        System.out.println("Capitalize words: " + advanced.capitalizeWords("hello world"));
        System.out.println("Reverse: " + advanced.reverse("hello"));
        System.out.println("Count 'll' in 'hello hello': " + advanced.countOccurrences("hello hello", "ll"));
        System.out.println("Is blank '  ': " + utils.isBlank("  "));
        System.out.println("Truncate: " + utils.truncate("Hello World", 5));
        System.out.println("Pad left: " + utils.padLeft("123", 5, '0'));

        // 11. String comparison
        System.out.println("\n--- 11. String Comparison ---");
        StringComparison comparison = new StringComparison();
        System.out.println("Equals 'hello' and 'hello': " + comparison.equals("hello", "hello"));
        System.out.println("Equals ignore case 'Hello' and 'hello': " + comparison.equalsIgnoreCase("Hello", "hello"));
        System.out.println("Common prefix of 'hello' and 'help': " + comparison.commonPrefix("hello", "help"));
        System.out.println("Levenshtein distance of 'kitten' and 'sitting': " + comparison.levenshteinDistance("kitten", "sitting"));

        System.out.println("\n=== All String Split and Join Examples Completed ===");
    }
}

// Android Java Regular Expression Examples
// Java standard library regex support

import java.util.*;
import java.util.regex.*;

// 1. Basic Pattern Matching
class RegexMatcher {

    // Check if pattern matches entire string
    public boolean matchesFullString(String text, String pattern) {
        return Pattern.matches(pattern, text);
    }

    // Check if pattern contains in string
    public boolean containsPattern(String text, String pattern) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        return m.find();
    }

    // Find first match
    public String findFirstMatch(String text, String pattern) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        if (m.find()) {
            return m.group();
        }
        return null;
    }

    // Find all matches
    public List<String> findAllMatches(String text, String pattern) {
        List<String> matches = new ArrayList<>();
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);

        while (m.find()) {
            matches.add(m.group());
        }

        return matches;
    }

    // Find matches with groups
    public List<List<String>> findGroupMatches(String text, String pattern) {
        List<List<String>> results = new ArrayList<>();
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);

        while (m.find()) {
            List<String> groups = new ArrayList<>();
            for (int i = 0; i <= m.groupCount(); i++) {
                groups.add(m.group(i));
            }
            results.add(groups);
        }

        return results;
    }
}

// 2. Common Validation Patterns
class StringValidator {

    // Validate email
    public boolean isValidEmail(String email) {
        String emailPattern = "^[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}$";
        return Pattern.matches(emailPattern, email);
    }

    // Validate phone number
    public boolean isValidPhoneNumber(String phone) {
        String phonePattern = "^\\+?[1-9]\\d{1,14}$";
        return Pattern.matches(phonePattern, phone);
    }

    // Validate URL
    public boolean isValidURL(String url) {
        String urlPattern = "^https?://[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}(/[^\\s]*)?$";
        return Pattern.matches(urlPattern, url);
    }

    // Validate IPv4 address
    public boolean isValidIPv4(String ip) {
        String ipPattern = "^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}" +
                          "(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$";
        return Pattern.matches(ipPattern, ip);
    }

    // Validate credit card (basic format)
    public boolean isValidCreditCard(String card) {
        String cardPattern = "^\\d{13,19}$";
        return Pattern.matches(cardPattern, card.replaceAll("\\s", ""));
    }

    // Validate hexadecimal color
    public boolean isValidHexColor(String color) {
        String colorPattern = "^#?([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$";
        return Pattern.matches(colorPattern, color);
    }

    // Validate strong password
    public boolean isStrongPassword(String password) {
        // At least 8 chars, 1 uppercase, 1 lowercase, 1 digit, 1 special
        String passwordPattern = "^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[@$!%*?&])[A-Za-z\\d@$!%*?&]{8,}$";
        return Pattern.matches(passwordPattern, password);
    }

    // Validate date format (YYYY-MM-DD)
    public boolean isValidDate(String date) {
        String datePattern = "^\\d{4}-\\d{2}-\\d{2}$";
        return Pattern.matches(datePattern, date);
    }

    // Validate username (alphanumeric, underscore, 3-20 chars)
    public boolean isValidUsername(String username) {
        String usernamePattern = "^[a-zA-Z0-9_]{3,20}$";
        return Pattern.matches(usernamePattern, username);
    }

    // Validate postal code (US format)
    public boolean isValidPostalCode(String code) {
        String postalPattern = "^\\d{5}(-\\d{4})?$";
        return Pattern.matches(postalPattern, code);
    }
}

// 3. Search and Extract
class RegexSearcher {

    // Extract all email addresses
    public List<String> extractEmails(String text) {
        String emailPattern = "[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}";
        return new RegexMatcher().findAllMatches(text, emailPattern);
    }

    // Extract all URLs
    public List<String> extractURLs(String text) {
        String urlPattern = "https?://[^\\s]+";
        return new RegexMatcher().findAllMatches(text, urlPattern);
    }

    // Extract all hashtags
    public List<String> extractHashtags(String text) {
        String hashtagPattern = "#\\w+";
        return new RegexMatcher().findAllMatches(text, hashtagPattern);
    }

    // Extract all mentions
    public List<String> extractMentions(String text) {
        String mentionPattern = "@\\w+";
        return new RegexMatcher().findAllMatches(text, mentionPattern);
    }

    // Extract numbers
    public List<Double> extractNumbers(String text) {
        String numberPattern = "-?\\d+\\.\\d+|-?\\d+";
        List<String> matches = new RegexMatcher().findAllMatches(text, numberPattern);
        List<Double> numbers = new ArrayList<>();

        for (String match : matches) {
            try {
                numbers.add(Double.parseDouble(match));
            } catch (NumberFormatException e) {
                // Skip invalid numbers
            }
        }

        return numbers;
    }

    // Extract quoted text
    public List<String> extractQuotedText(String text) {
        String quotePattern = "\"([^"]*)\"";
        List<List<String>> groups = new RegexMatcher().findGroupMatches(text, quotePattern);
        List<String> quotes = new ArrayList<>();

        for (List<String> group : groups) {
            if (group.size() > 1) {
                quotes.add(group.get(1));
            }
        }

        return quotes;
    }
}

// 4. Text Processing with Regex
class RegexTextProcessor {

    // Remove extra whitespace
    public String normalizeWhitespace(String text) {
        return text.replaceAll("\\s+", " ").trim();
    }

    // Remove all special characters
    public String removeSpecialCharacters(String text) {
        return text.replaceAll("[^a-zA-Z0-9\\s]", "");
    }

    // Remove all digits
    public String removeDigits(String text) {
        return text.replaceAll("\\d", "");
    }

    // Remove all letters
    public String removeLetters(String text) {
        return text.replaceAll("[a-zA-Z]", "");
    }

    // Replace multiple spaces with single space
    public String collapseSpaces(String text) {
        return text.replaceAll(" +", " ");
    }

    // Remove HTML tags
    public String stripHTMLTags(String text) {
        return text.replaceAll("<[^>]*>", "");
    }

    // Mask email addresses
    public String maskEmails(String text) {
        return text.replaceAll(
            "([A-Za-z0-9+_.-]+)@([A-Za-z0-9.-]+\\.[A-Za-z]{2,})",
            "***@$2"
        );
    }

    // Mask phone numbers
    public String maskPhoneNumbers(String text) {
        return text.replaceAll(
            "\\+?[1-9]\\d{1,14}",
            "***"
        );
    }

    // Sanitize filename
    public String sanitizeFilename(String filename) {
        return filename.replaceAll("[^a-zA-Z0-9._-]", "_");
    }
}

// 5. Regex Replacement with Callback
class RegexReplacer {

    // Replace with count
    public String replaceFirst(String text, String pattern, String replacement) {
        return text.replaceFirst(pattern, replacement);
    }

    // Replace all
    public String replaceAll(String text, String pattern, String replacement) {
        return text.replaceAll(pattern, replacement);
    }

    // Replace with function
    public String replaceWithCallback(String text, String pattern, java.util.function.Function<Matcher, String> callback) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        StringBuffer sb = new StringBuffer();

        while (m.find()) {
            m.appendReplacement(sb, callback.apply(m));
        }
        m.appendTail(sb);

        return sb.toString();
    }

    // Capitalize words after period
    public String capitalizeAfterPeriod(String text) {
        return replaceWithCallback(text, "\\.\\s*([a-z])", matcher -> {
            return ". " + matcher.group(1).toUpperCase();
        });
    }

    // Wrap URLs in links
    public String wrapURLsInLinks(String text) {
        String urlPattern = "(https?://[^\\s]+)";
        return replaceWithCallback(text, urlPattern, matcher -> {
            return "<a href=\"" + matcher.group(1) + "\">" + matcher.group(1) + "</a>";
        });
    }
}

// 6. Pattern Compilation and Reuse
class PatternCache {
    private Map<String, Pattern> cache = new HashMap<>();

    public Pattern getPattern(String regex) {
        if (!cache.containsKey(regex)) {
            cache.put(regex, Pattern.compile(regex));
        }
        return cache.get(regex);
    }

    public Matcher getMatcher(String regex, String text) {
        return getPattern(regex).matcher(text);
    }

    public boolean matches(String regex, String text) {
        return getPattern(regex).matcher(text).matches();
    }

    public boolean contains(String regex, String text) {
        return getPattern(regex).matcher(text).find();
    }
}

// Main demonstration
class RegexDemo {
    public static void demonstrateRegex() {
        System.out.println("=== Android Java Regular Expression Examples ===\n");

        // 1. Basic pattern matching
        System.out.println("--- 1. Basic Pattern Matching ---");
        RegexMatcher matcher = new RegexMatcher();
        String text = "The price is $123.45";

        System.out.println("Contains digits: " + matcher.containsPattern(text, "\\d+"));
        System.out.println("First digit match: " + matcher.findFirstMatch(text, "\\d+"));
        System.out.println("All matches for \\d+: " + matcher.findAllMatches(text, "\\d+"));

        // 2. Validation
        System.out.println("\n--- 2. String Validation ---");
        StringValidator validator = new StringValidator();

        System.out.println("Valid email '[email protected]': " + validator.isValidEmail("[email protected]"));
        System.out.println("Valid phone '+1234567890': " + validator.isValidPhoneNumber("+1234567890"));
        System.out.println("Valid URL 'https://example.com': " + validator.isValidURL("https://example.com"));
        System.out.println("Valid IPv4 '192.168.1.1': " + validator.isValidIPv4("192.168.1.1"));
        System.out.println("Valid hex color '#FF5733': " + validator.isValidHexColor("#FF5733"));
        System.out.println("Strong password 'Pass123!': " + validator.isStrongPassword("Pass123!"));
        System.out.println("Valid username 'user_123': " + validator.isValidUsername("user_123"));

        // 3. Extraction
        System.out.println("\n--- 3. Extract Information ---");
        RegexSearcher searcher = new RegexSearcher();

        String sampleText = "Contact us at [email protected] or [email protected]. " +
                           "Visit https://example.com for more info. " +
                           "Follow @user on Twitter! #example";

        System.out.println("Emails: " + searcher.extractEmails(sampleText));
        System.out.println("URLs: " + searcher.extractURLs(sampleText));
        System.out.println("Hashtags: " + searcher.extractHashtags(sampleText));
        System.out.println("Mentions: " + searcher.extractMentions(sampleText));

        String numbersText = "The values are 123.45, 67, and -89.5";
        System.out.println("Numbers: " + searcher.extractNumbers(numbersText));

        String quotedText = "He said \"Hello\" and she replied \"Hi\"";
        System.out.println("Quotes: " + searcher.extractQuotedText(quotedText));

        // 4. Text processing
        System.out.println("\n--- 4. Text Processing ---");
        RegexTextProcessor processor = new RegexTextProcessor();

        String messyText = "This    has   extra   spaces   ";
        System.out.println("Normalize: '" + processor.normalizeWhitespace(messyText) + "'");

        String specialChars = "Hello@#$%World123!";
        System.out.println("Remove special: '" + processor.removeSpecialCharacters(specialChars) + "'");
        System.out.println("Remove digits: '" + processor.removeDigits(specialChars) + "'");

        String html = "<p>This is <b>bold</b> text</p>";
        System.out.println("Strip HTML: '" + processor.stripHTMLTags(html) + "'");

        String emailText = "Contact [email protected] for info";
        System.out.println("Mask emails: '" + processor.maskEmails(emailText) + "'");

        // 5. Replacement
        System.out.println("\n--- 5. Regex Replacement ---");
        RegexReplacer replacer = new RegexReplacer();

        String replaceText = "The price is $100 and $200";
        System.out.println("Replace $ with €: " + replacer.replaceAll(replaceText, "\\$", "€"));

        String periodText = "hello. world. test. example";
        System.out.println("Capitalize after period: " + replacer.capitalizeAfterPeriod(periodText));

        String urlText = "Visit https://example.com and http://test.com";
        System.out.println("Wrap URLs: " + replacer.wrapURLsInLinks(urlText));

        // 6. Group matching
        System.out.println("\n--- 6. Group Matching ---");
        String dateText = "Date: 2024-12-28";
        List<List<String>> dateGroups = matcher.findGroupMatches(dateText, "(\\d{4})-(\\d{2})-(\\d{2})");
        System.out.println("Date groups: " + dateGroups);

        String nameText = "John Doe and Jane Smith";
        List<List<String>> nameGroups = matcher.findGroupMatches(nameText, "([A-Z][a-z]+) ([A-Z][a-z]+)");
        System.out.println("Name groups: " + nameGroups);

        System.out.println("\n=== All Regular Expression Examples Completed ===");
    }
}

// Android Java String Replacement Examples
// Java standard library string replacement methods

import java.util.*;
import java.util.regex.*;

// 1. Basic Replacement
class BasicReplacement {

    // Replace first occurrence
    public String replaceFirst(String text, String target, String replacement) {
        return text.replaceFirst(Pattern.quote(target), replacement);
    }

    // Replace all occurrences
    public String replaceAll(String text, String target, String replacement) {
        return text.replaceAll(Pattern.quote(target), replacement);
    }

    // Replace using char (single character)
    public String replaceChar(String text, char oldChar, char newChar) {
        return text.replace(oldChar, newChar);
    }

    // Replace using CharSequence
    public String replaceSequence(String text, String target, String replacement) {
        return text.replace(target, replacement);
    }

    // Replace with case-insensitive
    public String replaceIgnoreCase(String text, String target, String replacement) {
        Pattern p = Pattern.compile(target, Pattern.CASE_INSENSITIVE);
        Matcher m = p.matcher(text);
        return m.replaceAll(replacement);
    }
}

// 2. Conditional Replacement
class ConditionalReplacement {

    // Replace if condition met
    public String replaceIf(String text, String target, String replacement, boolean condition) {
        if (condition) {
            return text.replace(target, replacement);
        }
        return text;
    }

    // Replace with map lookup
    public String replaceWithMap(String text, Map<String, String> replacements) {
        String result = text;
        for (Map.Entry<String, String> entry : replacements.entrySet()) {
            result = result.replace(entry.getKey(), entry.getValue());
        }
        return result;
    }

    // Replace with function
    public String replaceWithFunction(String text, String pattern, java.util.function.Function<Matcher, String> func) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        StringBuffer sb = new StringBuffer();

        while (m.find()) {
            m.appendReplacement(sb, func.apply(m));
        }
        m.appendTail(sb);

        return sb.toString();
    }

    // Replace only whole words
    public String replaceWholeWords(String text, String target, String replacement) {
        String pattern = "\\b" + Pattern.quote(target) + "\\b";
        return text.replaceAll(pattern, replacement);
    }
}

// 3. Multiple Replacements
class MultipleReplacements {

    // Chain of replacements
    public String chainReplace(String text, List<ReplacementRule> rules) {
        String result = text;
        for (ReplacementRule rule : rules) {
            result = result.replaceAll(rule.pattern, rule.replacement);
        }
        return result;
    }

    // Replace multiple targets at once
    public String replaceMultiple(String text, String[] targets, String replacement) {
        String result = text;
        for (String target : targets) {
            result = result.replace(target, replacement);
        }
        return result;
    }

    // Parallel replacement
    public Map<String, String> parallelReplace(Map<String, String> inputs, String target, String replacement) {
        Map<String, String> results = new HashMap<>();
        for (Map.Entry<String, String> entry : inputs.entrySet()) {
            results.put(entry.getKey(), entry.getValue().replace(target, replacement));
        }
        return results;
    }

    public static class ReplacementRule {
        public String pattern;
        public String replacement;

        public ReplacementRule(String pattern, String replacement) {
            this.pattern = pattern;
            this.replacement = replacement;
        }
    }
}

// 4. Advanced Replacement
class AdvancedReplacement {

    // Swap two substrings
    public String swapSubstrings(String text, String first, String second) {
        return text.replace(first, "\\0").replace(second, first).replace("\\0", second);
    }

    // Rotate replacements
    public String rotateReplacements(String text, String[] values) {
        String result = text;
        int index = 0;
        Pattern p = Pattern.compile("\\{\}");

        Matcher m = p.matcher(result);
        StringBuffer sb = new StringBuffer();

        while (m.find()) {
            String replacement = values[index % values.length];
            m.appendReplacement(sb, Matcher.quoteReplacement(replacement));
            index++;
        }
        m.appendTail(sb);

        return sb.toString();
    }

    // Template replacement
    public String replaceTemplate(String template, Map<String, String> values) {
        String result = template;
        for (Map.Entry<String, String> entry : values.entrySet()) {
            String placeholder = "\ + entry.getKey() + ";
            result = result.replace(placeholder, entry.getValue());
        }
        return result;
    }

    // Number placeholders
    public String replaceNumberedPlaceholders(String template, String[] values) {
        String result = template;
        for (int i = 0; i < values.length; i++) {
            String placeholder = "%" + (i + 1);
            result = result.replace(placeholder, values[i]);
        }
        return result;
    }
}

// 5. Text Cleanup
class TextCleanup {

    // Remove accents
    public String removeAccents(String text) {
        String normalized = java.text.Normalizer.normalize(text, java.text.Normalizer.Form.NFD);
        return normalized.replaceAll("\\p{M}", "");
    }

    // Normalize line endings
    public String normalizeLineEndings(String text) {
        return text.replaceAll("\\r\\n", "\\n").replaceAll("\\r", "\\n");
    }

    // Trim leading/trailing whitespace from each line
    public String trimLines(String text) {
        String[] lines = text.split("\\n");
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < lines.length; i++) {
            if (i > 0) {
                sb.append("\\n");
            }
            sb.append(lines[i].trim());
        }

        return sb.toString();
    }

    // Remove empty lines
    public String removeEmptyLines(String text) {
        return text.replaceAll("^\\s*\\n|\\n\\s*$", "");
    }

    // Collapse multiple consecutive spaces
    public String collapseSpaces(String text) {
        return text.replaceAll(" +", " ");
    }

    // Remove control characters
    public String removeControlCharacters(String text) {
        return text.replaceAll("\\p{C}", "");
    }

    // Sanitize for filename
    public String sanitizeFilename(String filename) {
        return filename.replaceAll("[^a-zA-Z0-9._-]", "_");
    }

    // Convert to title case
    public String toTitleCase(String text) {
        String[] words = text.split("\\s+");
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < words.length; i++) {
            if (i > 0) {
                sb.append(" ");
            }
            if (!words[i].isEmpty()) {
                sb.append(Character.toUpperCase(words[i].charAt(0)));
                if (words[i].length() > 1) {
                    sb.append(words[i].substring(1).toLowerCase());
                }
            }
        }

        return sb.toString();
    }
}

// 6. Smart Replacement
class SmartReplacement {

    // Replace with incrementing counter
    public String replaceWithCounter(String text, String pattern, int start) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        StringBuffer sb = new StringBuffer();
        int[] counter = {start};

        while (m.find()) {
            m.appendReplacement(sb, String.valueOf(counter[0]++));
        }
        m.appendTail(sb);

        return sb.toString();
    }

    // Replace with alternating values
    public String replaceAlternating(String text, String pattern, String[] values) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        StringBuffer sb = new StringBuffer();
        int[] index = {0};

        while (m.find()) {
            m.appendReplacement(sb, values[index[0] % values.length]);
            index[0]++;
        }
        m.appendTail(sb);

        return sb.toString();
    }

    // Conditional replacement based on context
    public String replaceConditional(String text, String pattern, java.util.function.Function<Matcher, String> condition) {
        Pattern p = Pattern.compile(pattern);
        Matcher m = p.matcher(text);
        StringBuffer sb = new StringBuffer();

        while (m.find()) {
            String replacement = condition.apply(m);
            if (replacement != null) {
                m.appendReplacement(sb, replacement);
            }
        }
        m.appendTail(sb);

        return sb.toString();
    }
}

// Main demonstration
class StringReplacementDemo {
    public static void demonstrateStringReplacement() {
        System.out.println("=== Android Java String Replacement Examples ===\n");

        // 1. Basic replacement
        System.out.println("--- 1. Basic Replacement ---");
        BasicReplacement basic = new BasicReplacement();

        String text1 = "Hello World, World is great";
        System.out.println("Original: " + text1);
        System.out.println("Replace first 'World': " + basic.replaceFirst(text1, "World", "Java"));
        System.out.println("Replace all 'World': " + basic.replaceAll(text1, "World", "Java"));
        System.out.println("Replace char 'o' with '0': " + basic.replaceChar(text1, 'o', '0'));

        // 2. Case-insensitive replacement
        String text2 = "Hello HELLO HeLLo hELLo";
        System.out.println("\nOriginal: " + text2);
        System.out.println("Replace 'hello' (case-insensitive): " + basic.replaceIgnoreCase(text2, "hello", "Java"));

        // 3. Conditional replacement
        System.out.println("\n--- 2. Conditional Replacement ---");
        ConditionalReplacement conditional = new ConditionalReplacement();

        String text3 = "The price is $100";
        System.out.println("Original: " + text3);
        System.out.println("Replace if true: " + conditional.replaceIf(text3, "$100", "$200", true));
        System.out.println("Replace if false: " + conditional.replaceIf(text3, "$100", "$200", false));

        Map<String, String> replacements = new HashMap<>();
        replacements.put("apple", "fruit");
        replacements.put("carrot", "vegetable");
        String text4 = "I like apple and carrot";
        System.out.println("Replace with map: " + conditional.replaceWithMap(text4, replacements));

        // 4. Whole word replacement
        String text5 = "The cat and catalog are different";
        System.out.println("\nOriginal: " + text5);
        System.out.println("Replace whole word 'cat': " + conditional.replaceWholeWords(text5, "cat", "dog"));
        System.out.println("Replace all 'cat': " + text5.replace("cat", "dog"));

        // 5. Multiple replacements
        System.out.println("\n--- 3. Multiple Replacements ---");
        MultipleReplacements multiple = new MultipleReplacements();

        List<MultipleReplacements.ReplacementRule> rules = new ArrayList<>();
        rules.add(new MultipleReplacements.ReplacementRule("&", "&amp;"));
        rules.add(new MultipleReplacements.ReplacementRule("<", "&lt;"));
        rules.add(new MultipleReplacements.ReplacementRule(">", "&gt;"));

        String html = "5 < 10 & 10 > 5";
        System.out.println("HTML escape: " + multiple.chainReplace(html, rules));

        // 6. Advanced replacement
        System.out.println("\n--- 4. Advanced Replacement ---");
        AdvancedReplacement advanced = new AdvancedReplacement();

        String template1 = "Hello ${name}, welcome to ${place}";
        Map<String, String> values1 = new HashMap<>();
        values1.put("name", "John");
        values1.put("place", "Tokyo");
        System.out.println("Template replacement: " + advanced.replaceTemplate(template1, values1));

        String template2 = "Dear %1, your order %2 is ready";
        System.out.println("Numbered placeholders: " + advanced.replaceNumberedPlaceholders(template2, new String[]{"John", "#12345"}));

        // 7. Text cleanup
        System.out.println("\n--- 5. Text Cleanup ---");
        TextCleanup cleanup = new TextCleanup();

        String messyText = "  Hello    World  \n\n  Test  \n";
        System.out.println("Original: '" + messyText + "'");
        System.out.println("Normalize: '" + cleanup.normalizeLineEndings(messyText) + "'");
        System.out.println("Trim lines: '" + cleanup.trimLines(messyText) + "'");
        System.out.println("Collapse spaces: '" + cleanup.collapseSpaces("Hello    World   Test") + "'");
        System.out.println("Remove accents: " + cleanup.removeAccents("café résumé naïve"));
        System.out.println("Title case: " + cleanup.toTitleCase("hello world from java"));

        // 8. Smart replacement
        System.out.println("\n--- 6. Smart Replacement ---");
        SmartReplacement smart = new SmartReplacement();

        String counterText = "Item _, Item _, Item _";
        System.out.println("Replace with counter: " + smart.replaceWithCounter(counterText, "_", 1));

        String alternatingText = "Color _, Color _, Color _";
        System.out.println("Alternating colors: " + smart.replaceAlternating(alternatingText, "_", new String[]{"red", "blue", "green"}));

        // 9. Context-aware replacement
        String contextText = "price: 100, cost: 200, value: 300";
        String result = smart.replaceConditional(contextText, "\\d+", matcher -> {
            int num = Integer.parseInt(matcher.group());
            return String.valueOf(num * 2);
        });
        System.out.println("Double numbers: " + result);

        System.out.println("\n=== All String Replacement Examples Completed ===");
    }
}