public void print() {
        if(this instanceof AddOp) {
            System.out.print("+ ");
        } else if(this instanceof SubOp) {
            System.out.print("- ");
        } else if(this instanceof MulOp) {
            System.out.print("* ");
        } else if(this instanceof DivOp) {
            System.out.print("/ ");
        } else if(this instanceof RParOp) {
            System.out.print(") ");
        } else if(this instanceof LParOp) {
            System.out.print("( ");
        } else if(this instanceof EqualOp) {
            System.out.print("= ");
        }
    }