import java.util.Scanner;
public class test{
private static void input(){
String str = "";
int count = 0;
System.out.println("请输入一个三个字符且包含有大写字母或数字或小数点任意一种或多种字符的的字符串:");
str = new Scanner(System.in).next();
for (int i = 0; i < str.length(); i++) {
if (((int)str.substring(i, i+1).charAt(0)>=48 && (int)str.substring(i, i+1).charAt(0)<= 57)
||((int)str.substring(i, i+1).charAt(0)>=65 && (int)str.substring(i, i+1).charAt(0)<= 90)
|| (int)str.substring(i, i+1).charAt(0) == 46 ) {
count++;
}
}
if (count!=str.length() || str.length()!=3) {
System.out.println("非法输入!");
input();
}else{
System.out.println("输入正确!");
}
}
public static void main(String[] args) {
input();
}
}
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