Java code to check if input is a logical sentence

I am new to using java and am running into problems with creating a program that tells me if my input is a logical sentence. Here is what I have so far (I am sure there are a couple of mistakes):

public class propLogic {

    String stringName;

    public propLogic(string stringA){
        stringName = stringA;
        }


    public static void main(String[] args) {

        propLogic one = new propLogic("hello");

        if (stringName.equals("p")) {
            System.out.println("Valid logical sentence");
        } else if (stringName.equals("~p")) {
            System.out.println("Valid logical sentence");
        } else if (stringName.equals("p & v")) {
            System.out.println("Valid logical sentence");
        } else {
            System.out.println("Not a valid logical sentence");
        }

    }
}