クソコード

gistfile1.java

class PolandNotation implements Calculable
{
    private transient String[] tokens;
	private transient int index = 0;
	private CalculableNode root;

	public PolandNotation(String str)
	{
		tokens = str.split(" ");
		root = createNode();
	}
	private CalculableNode createNode()
	{
		String token = tokens[index++];
		if(token.equals("+"))
			return new AddNode(createNode(), createNode());
		if(token.equals("-"))
			return new SubtractNode(createNode(), createNode());
		if(token.equals("*"))
			return new MultiplyNode(createNode(), createNode());
		if(token.equals("/"))
			return new DivideNode(createNode(), createNode());
		double d = Double.parseDouble(token);
		return new NumberNode(d);
	}

	@Override
	public double calc()
	{
		return root.calc();
	}

	@Override
	public String toString()
	{
		return root.toString();
	}
}
interface Calculable
{
	public double calc();
}
abstract class CalculableNode implements Calculable
{
	@Override
	public abstract String toString();
}
class NumberNode extends CalculableNode
{
	private final double value;

	public NumberNode(double value)
	{
		this.value = value;
	}

	@Override
	public double calc()
	{
		return value;
	}

	@Override
	public String toString()
	{
		return String.valueOf(value);
	}
}
abstract class OperationNode extends CalculableNode
{
	protected Calculable left;
	protected Calculable right;

	public OperationNode(Calculable left, Calculable right)
	{
		this.left = left;
		this.right = right;
	}
}
class AddNode extends OperationNode
{
	public AddNode(Calculable left, Calculable right)
	{
		super(left, right);
	}

	@Override
	public double calc()
	{
		return left.calc() + right.calc();
	}

	@Override
	public String toString()
	{
		return new StringBuilder("+ ").append(left).append(' ').append(right).toString();
	}
}
class SubtractNode extends OperationNode
{
	public SubtractNode(Calculable left, Calculable right)
	{
		super(left, right);
	}

	@Override
	public double calc()
	{
		return left.calc() - right.calc();
	}

	@Override
	public String toString()
	{
		return new StringBuilder("- ").append(left).append(' ').append(right).toString();
	}
}
class MultiplyNode extends OperationNode
{
	public MultiplyNode(Calculable left, Calculable right)
	{
		super(left, right);
	}

	@Override
	public double calc()
	{
		return left.calc() * right.calc();
	}

	@Override
	public String toString()
	{
		return new StringBuilder("* ").append(left).append(' ').append(right).toString();
	}
}
class DivideNode extends OperationNode
{
	public DivideNode(Calculable left, Calculable right)
	{
		super(left, right);
	}

	@Override
	public double calc()
	{
		double divisor = right.calc();
		if(Double.isNaN(divisor/divisor)) throw new ArithmeticException("/ by zero");
		return left.calc() / divisor;
	}

	@Override
	public String toString()
	{
		return new StringBuilder("/ ").append(left).append(' ').append(right).toString();
	}
}