如何使用regex、Java查找换行后开始的单词?

我有一个输入字符串，由几行组成，例如：

When I was younger I never needed And I was always OK but it was a long Time Ago 问题是将长度大于3的所有单词的首字母反转。即输出必须是以下内容：

when I Was Younger I Never Needed and I Was Always OK But it Was a Long time ago 代码：

import java.util.regex.*;

public class Part3_1 {

public static void main(String[] args) {
    String str = "When I was younger\r\nI never needed\r\nAnd I was always OK\r\nbut it was a long Time Ago";
    System.out.println(convert(str));

}

public static String convert(String str) {
    String result = "";
    String[] strings = str.split(" ");
    String regexLowerCase = "\\b[a-z]{3,}\\b";
    String regexLowerCaseInitial = "(\\r\\n)[a-z]{3,}\\b";
    String regexUpperCase = "\\b([A-Z][a-z]{2,})+\\b";
    String regexUpperCaseInitial = "(\\r\\n)([A-Z][a-z]{2,})\\b";
    Pattern patternLowerCase = Pattern.compile(regexLowerCase, Pattern.MULTILINE);
    Pattern patternUpperCase = Pattern.compile(regexUpperCase, Pattern.MULTILINE);
    Pattern patternLowerCaseInitial = Pattern.compile(regexLowerCaseInitial, Pattern.MULTILINE);
    Pattern patternUpperCaseInitial = Pattern.compile(regexUpperCaseInitial, Pattern.MULTILINE);

    for (int i = 0; i < strings.length; i++) {
        Matcher matcherLowerCase = patternLowerCase.matcher(strings[i]);
        Matcher matcherUpperCase = patternUpperCase.matcher(strings[i]);
        Matcher matcherLowerCaseInitial = patternLowerCaseInitial.matcher(strings[i]);
        Matcher matcherUpperCaseInitial = patternUpperCaseInitial.matcher(strings[i]);
        char[] words = strings[i].toCharArray();
        if (matcherLowerCase.find() || matcherLowerCaseInitial.find()) {
            char temp = Character.toUpperCase(words[0]);
            words[0] = temp;
            result += new String(words);
        } else if (matcherUpperCase.find() || matcherUpperCaseInitial.find()) {
            char temp = Character.toLowerCase(words[0]);
            words[0] = temp;
            result += new String(words);
        } else {
            result += new String(words);
        }

        if (i < strings.length - 1) { 
            result += " "; 
        } 
    }
    return result;
}

} 这里：

"\b[a-z]{3,}\b" 是一个正则表达式，选择所有小写且长度为3个或更多符号的单词， "\b([A-Z][a-z]{2,})+\b" 是一个正则表达式，选择所有长度从3个或更多符号开始的大写字母。 这两个正则表达式都可以正常工作，但是当我们有换行符时，它们不起作用。我的程序执行的输出如下：

when I Was Younger I Never Needed And I Was Always OK but it Was a Long Time ago 据我所知，这些正则表达式不能分别从required \r\nAnd和OK\r\nbut中选择单词和And和but。

要解决此错误，我尝试添加新的正则表达式"(\r\n)[a-z]{3,}\b"和"(\r\n)([A-Z][a-z]{2,})\b"，但它们不起作用。

如何组成正则表达式，在换行后选择单词？