//第一種方式
import java.util.regex.Pattern;
import java.util.regex.Matcher;

...
// 4 different combinaisons
Pattern CRLF = Pattern.compile("(\r\n|\r|\n|\n\r)");
Matcher m = CRLF.matcher(myString);
 
if (m.find()) {
  newString = m.replaceAll("<br>");
}
//第二種方式

newString = myString.replaceAll("(\r\n|\r|\n|\n\r)", "<br>");
 

測試

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

public class StringTest {

	public static String sss(String myString){
		String newString=null;
		Pattern CRLF = Pattern.compile("(\r\n|\r|\n|\n\r)");
		Matcher m = CRLF.matcher(myString);
		if (m.find()) {
		  newString = m.replaceAll("<br>");
		}
		return newString;
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String aaa="sdfsfdsfsdf\r\n,dsfsdfsdf\r\n";
		//aaa.replace("s", "x");
		String newStr=sss(aaa);
		System.out.println(newStr);
	}

}