如何在java中用给定的替换图替换一些单词？

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class WordReplacement {
    public static void main(String[] args) {
        // 定义替换图
        Map<String, String> replacementMap = new HashMap<>();
        replacementMap.put("apple", "fruit");
        replacementMap.put("car", "vehicle");

        // 待替换的字符串
        String input = "I have an apple and a car.";

        // 构建正则表达式
        String patternString = "\\b(" + String.join("|", replacementMap.keySet()) + ")\\b";
        Pattern pattern = Pattern.compile(patternString);

        // 执行替换
        Matcher matcher = pattern.matcher(input);
        StringBuffer output = new StringBuffer();
        while (matcher.find()) {
            matcher.appendReplacement(output, replacementMap.get(matcher.group()));
        }
        matcher.appendTail(output);

        // 输出结果
        System.out.println(output.toString());
    }
}