Regular Expression Check (aa)*+(aaa)*

package regularexpression.check;

import java.util.Scanner;

public class RegularExpressionCheck {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println(“The R.E is (aa)*+(aaa)*”);
System.out.println(“Enter the string”);
String str = sc.nextLine();
System.out.println(“The condition for R.E is to have a in multiple of 2 or 3 or no a and no other symbol “);
int length = str.length();
int flag=0;
System.out.println(“length =” + length);

for (int i = 0; i < length; i++) {
if(str.charAt(i)!=’a’)
{
flag=1;

}
else
{ if(length%2==0||length%3==0||str.isEmpty())
{
flag=2;

}
else
{
flag=1;

}
}
}
if(flag==2||str.contains(“e”)|| str.isEmpty())
{
System.out.println(“RE ACCEPTED”);
}
else
{
System.out.println(“RE REJECTED”);
}

                                                        OUTPUT

The R.E is (aa)*+(aaa)*
Enter the string

The condition for R.E is to have a in multiple of 2 or 3 or no a and no other symbol
length =0
RE ACCEPTED             //since no char inserted

The R.E is (aa)*+(aaa)*
Enter the string
e
The condition for R.E is to have a in multiple of 2 or 3 or no a and no other symbol
length =1
RE ACCEPTED      //e represents epsilline

The R.E is (aa)*+(aaa)*
Enter the string
aaaaa
The condition for R.E is to have a in multiple of 2 or 3 or no a and no other symbol
length =5
RE REJECTED