java字符串寻找并替换的问题

各位大婶们

 String columnName = "user_name";
// .....
// 最后想得到columnName = userName, 
// 如果是user_first_name 转换成userFirstName 

public static void main(String[] args) {
String columnName = "user_name_mmm";
//分组 根据_
String[] arr = columnName.split("_");
StringBuilder sb= new StringBuilder();
for(int i =0;i<arr.length;i++){
sb.append(arr[i]);
}
System.out.println(sb.toString());
//结果usernamemmm
}

下划线转驼峰。http://www.cnblogs.com/javasharp/p/4622413.html

public static void main(String[] args) {
try{
String columnName = "user_first_name";
String[] arr = columnName.split("_");
StringBuilder sb= new StringBuilder();
for(int i =0;i<arr.length;i++){
if(i==0){
sb.append(arr[i]);
}else{
String first = arr[i].substring(0, 1).toUpperCase();
String rest = arr[i].substring(1, arr[i].length());
sb.append(new StringBuffer(first).append(rest));
}

}
System.out.println(sb.toString());
}catch(Exception e){
e.printStackTrace();
}
}

======输出结果：userFirstName