三种用于将字符串前面补足零的方法

本帖最后由舒远于 2012-9-13 17:30 编辑

/**
* 三种实现字符串前面补零的算法
*/
public class RegTest {
public static void main(String[] args) {
System.out.println(replace("123", 10));
System.out.println(addByLength("111222333", 10));
System.out.println(recursion ("123", 10));
}
public static String replace(String no, int a) {
String str = no;
String zero = "";
for (int i = 0; i < a; i++) {
zero += "0";
}
return str.replaceAll("(\\d+)", zero + "$1").replaceAll("0*(\\d{" + a + "})", "$1");
}
public static String addByLength(String a, int b) {
String r = a;
int len = b - r.length();
for (int i = 0; i < len; i++) {
r = "0" + r;
}
return r;
}
public static String recursion(String a, int b) {
if (b <= a.length())
return a;
else {
return "0" + recursion(a, --b);
}
}
}