Javaエスケープ処理の10ステップマスターガイド 初心者向け

public class EscapeExample {
    public static void main(String[] args) {
        String text = "彼は"Javaの基本を学ぶ"と言った。";
        System.out.println(text);
    }
}

public class QuoteEscapeExample {
    public static void main(String[] args) {
        String escapedString = "これは"エスケープ処理"の例です。";
        System.out.println(escapedString);
    }
}

public class SpecialCharacterEscape {
    public static void main(String[] args) {
        String originalText = "<div>Javaエスケープ処理</div>";
        String escapedText = originalText
                .replace("&", "&amp;")
                .replace("<", "&lt;")
                .replace(">", "&gt;")
                .replace(""", "&quot;")
                .replace("'", "&#39;");
        System.out.println("エスケープ後のテキスト: " + escapedText);
    }
}

public class EscapeProcess {
    public static void main(String[] args) {
        String original = "Hello <World>";
        String escaped = original.replace("&", "&amp;")
                                 .replace("<", "&lt;")
                                 .replace(">", "&gt;");
        System.out.println("元の文字列: " + original);
        System.out.println("エスケープ処理後の文字列: " + escaped);
    }
}

import org.apache.commons.text.StringEscapeUtils;

public class SecurityEscapeExample {
    public static void main(String[] args) {
        String userInput = "<script>alert('XSS');</script>";
        String safeOutput = StringEscapeUtils.escapeHtml4(userInput);
        System.out.println("安全な出力: " + safeOutput);
    }
}

public class EscapePerformance {
    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();

        for (int i = 0; i < 100_000; i++) {
            String escapedString = escapeHtml("Javaエスケープ処理テスト<" + i + ">");
        }

        long endTime = System.currentTimeMillis();
        System.out.println("処理時間: " + (endTime - startTime) + "ミリ秒");
    }

    public static String escapeHtml(String input) {
        return input.replace("&", "&amp;")
                    .replace("<", "&lt;")
                    .replace(">", "&gt;")
                    .replace(""", "&quot;")
                    .replace("'", "&#39;");
    }
}

public class EscapeProcessing {
    public static String escapeHtml(String str) {
        if (str == null) {
            return null;
        }
        StringBuilder escapedStr = new StringBuilder(str.length());
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            switch (c) {
                case '&': escapedStr.append("&amp;"); break;
                case '<': escapedStr.append("&lt;"); break;
                case '>': escapedStr.append("&gt;"); break;
                case '"': escapedStr.append("&quot;"); break;
                case ''': escapedStr.append("&#39;"); break;
                default: escapedStr.append(c);
            }
        }
        return escapedStr.toString();
    }

    public static void main(String[] args) {
        String input = "Hello & Welcome to the <Java> World!";
        String output = escapeHtml(input);
        System.out.println("Original String: " + input);
        System.out.println("Escaped String: " + output);
    }
}

public class CustomEscape {
    public static String customEscape(String input) {
        if (input == null || input.isEmpty()) {
            return input;
        }

        StringBuilder result = new StringBuilder(input.length());
        for (char c : input.toCharArray()) {
            if (c == '<') {
                result.append("&lt;");
            } else if (c == '>') {
                result.append("&gt;");
            } else {
                result.append(c);
            }
        }
        return result.toString();
    }

    public static void main(String[] args) {
        String text = "<div>Hello Java</div>";
        System.out.println(customEscape(text));
    }
}

public class EscapeProcessingExtension {
    public static String customEscape(String input) {
        if (input == null) {
            return null;
        }

        StringBuilder escapedString = new StringBuilder(input.length());
        for (char c : input.toCharArray()) {
            switch (c) {
                case '<': escapedString.append("&lt;"); break;
                case '>': escapedString.append("&gt;"); break;
                case '&': escapedString.append("&amp;"); break;
                case '"': escapedString.append("&quot;"); break;
                case ''': escapedString.append("&#39;"); break;
                default: escapedString.append(c);
            }
        }
        return escapedString.toString();
    }

    public static void main(String[] args) {
        String originalString = "Hello <World> & 'Java'";
        String escapedString = customEscape(originalString);
        System.out.println("元の文字列: " + originalString);
        System.out.println("エスケープ後の文字列: " + escapedString);
    }
}

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

public class FileEscapeExample {
    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("example.txt"))) {
            String line;
            while ((line = br.readLine()) != null) {
                String escapedLine = line.replace("&", "&")
                                         .replace("<", "&lt;")
                                         .replace(">", "&gt;")
                                         .replace(""", "&quot;")
                                         .replace("'", "&#39;");
                System.out.println(escapedLine);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.IOException;
import java.io.PrintWriter;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.apache.commons.text.StringEscapeUtils;

@WebServlet("/FormHandler")
public class FormHandler extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String userInput = request.getParameter("userInput");
        String escapedInput = StringEscapeUtils.escapeHtml4(userInput);

        response.setContentType("text/html; charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.println("<html><body>");
        out.println("入力されたデータ: " + escapedInput);
        out.println("</body></html>");
    }
}

public static String customEscape(String input) {
    if (input == null) {
        return "";
    }
    return input.replace("&", "&")
                .replace("<", "&lt;")
                .replace(">", "&gt;")
                .replace(""", "&quot;")
                .replace("'", "&#39;");
}

public class LogEscapeExample {
    public static void main(String[] args) {
        String input = "JavanEscapetGuide";
        String safeLog = input.replace("r", "\r")
                              .replace("n", "\n")
                              .replace("t", "\t");
        System.out.println(safeLog);
    }
}