Return the uppercase letters of a string

Uppercase.java

/*
* Return the uppercase letters of a string. Useful to return an acronym.
* By Javier Santos
* https://gist.github.com/javiersantos/58b7aa21338082d6c850
*/

public String getUppercase(String str) {
	String res = "";
	
	String[] split = str.split(" ");
	for(int i=0; i<=split.length-1; i++){
		String auxStr = split[i].trim();
		if(Character.isUpperCase(auxStr.charAt(0))){
		  char aux = auxStr.charAt(0);
		  res = res + aux + ", ";
		}
	}
	return res;
}