java 中字符串的比较大小

String a="b123";
String b="b124";
String d="b122";
String e="b123";
int c=a.compareTo(b);
System.out.println(c);//-1
c=a.compareTo(d);
System.out.println(c);//0
c=a.compareTo(e);
System.out.println(c);//1