Addition

public class Addition extends BinaryExpression {
    Expression left;
    Expression right;

    public Expression left() {
        return left;
    }

    public Expression right() {
        return right;
    }

    public Addition(Expression _left, Expression _right)
    {
        left = _left;
        right = _right;
    }

    public int evaluate()
    {
        return this.left.evaluate() + this.right.evaluate();
    }

    @Override
    public String toString() {
        return this.left.toString() + "+" + this.right.toString();
    }
}