I am working to debug this code. I know I can use the Character.isDigit() to change from a char type to boolean, but when I use it I am still getting an error. Please help.

public class CheckInteger extends ConsoleProgram

{

public void run()

{

// Testing Code

System.out.println("'abc' is an integer: " + isInteger("abc"));

System.out.println("'356' is an integer: " + isInteger("356"));

System.out.println("'r2d2' is an integer: " + isInteger("r2d2"));

}

public boolean isInteger(String str)

{

// Edge case. "" is not an integer

if (str.equals(""))

{

return false;

}

for (int i = 0; i < str.length(); i++)

{

String ch = str.substring(i, i+1);

if (Character.isDigit(ch))

{

return false;

}

}

return true;

}

}