java中String截取字符串

public class B {
public static void main(String[] args){
String attachmentUrl="asdfklasdf/3333";
String	b = attachmentUrl.substring(attachmentUrl
.lastIndexOf("/"));
System.out.println(attachmentUrl
.lastIndexOf("/"));
System.out.println("b======"+b);

String	c = attachmentUrl.substring(attachmentUrl
.lastIndexOf("/")+1);//最后一个"/"所在位置加1
System.out.println(attachmentUrl
.lastIndexOf("/"));
System.out.println("c======"+c);
}
}
=================
10
b======/3333
10
c======3333