How can I compare a char to a string or sequence of chars?

Question

import java.util.Scanner;
public class Program
{
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
String s1 = cin.nextLine();
int n = s1.length();
int j;
int k = 0;
int i =0;

char[] s = new char[n];

for (j = 0; j <= n; j++) {
if (s1.charAt(j) == '@!#$%^') {
if (j - 1 < 0)

break;

s[i] = s1.charAt(j - 1);
i++;
k++;
}

}
for(i=0;i<=k;i++)
System.out.println(s[i]);
cin.close();}
}

// with only one char ('@') the program have no errors but when I run it :
"Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 2
at java.base/java.lang.StringLatin1.charAt(Unknown Source)
at java.base/java.lang.String.charAt(Unknown Source)
at sololearn.RemoveChars.main(RemoveChars.java:18)
"

Answer 1

error is clear
"string index out of range"
in the first for loop
for(j=0; j<n; j++)

j should be less than n and not equal to n
as n is the length, so index of last enement is n-1