正则表达式引入概念

package regular;

import java.util.Scanner;

public class RegularDemo1 {

/**
* @正则表达式（引入概念）
*/
public static void main(String[] args) {
checkQQ_2();
}

public static void checkQQ_2(){
Scanner sc = new Scanner(system.in);
String qq = sc.nextLine();

String regex = "[1-9][0-9]{4,14}";

boolean flag = qq.matches(regex);
if(flag)
System.out.println("qq:"+qq +" is OK");
else
System.out.println(qq+":nonono");

}

/*

*/
public static void checkQQ_1(){
Scanner sc = new Scanner(system.in);

String qq = sc.nextLine();
int len = qq.length();
if(len>=5 && len<=15){

if(!qq.startsWith("0")){
/*方法二
try{

Long l = Long.parseLong(qq);
System.out.println("qq:"+qq);

}catch(NumberFormatException e){

System.out.println("出现非法字符");
}
*/

/*方法一
char[] arr = qq.tochararray();
boolean flag = true;
for(int i=0;i<arr.length;i++){
if(!(arr[i]>='0' && arr[i]<='9')){
flag=false;
break;
}
}
if(flag){
System.out.println("qq:"+qq);
}
else{
System.out.println("出现非法字符");
}
*/
}
else
{
System.out.println("不可以以零开头");
}

}
else
{
System.out.println("长度错误");
}
}

}