字符串首字母大写

public class Upper{
public static void main(String args[]){
String a = "good";
System.out.println(firstToUpper(a));
}
public static String firstToUpper(String str){
if(str!=null&&Character.isLowerCase(str.charAt(0))){
char[] charArray = str.toCharArray();
if(charArray!=null){
charArray[0]-=32;
return String.valueOf(charArray);
}
}
return str;
}
}