termnode.java

超级多项式计算器

import java.util.Vector;

/**Class TermNode<br/>
  *This class is data type to store the term of the polynomial
  *It contians several attributes such as coefficient,veriable 
  *and exponent.Also it contains the mothod to analyse the expression so to ensure the coefficient and variables.
  *@author zhlmmc
  *@version 1.0
  */

public class TermNode
{
	/**the term's simplest expression
	  */
	String s = "";

	/**the term's coefficient
	  */
	private long coefficient;

	private int pos;

	Vector variableName = new Vector();
	Vector exponent = new Vector();
	
	/**
	  *constructors
	  *TermNode() receive no arguments
	  */
	public TermNode()
	{
		coefficient = 0;
		pos = 0;		
	}

	/**
	  *constructors
	  *TermNode(String input)
	  *@param input the term's expression
	  */

	public TermNode(String input)
	{
		this();
		s = analyse(input);
		
	}
	
	/**
	  *method analyse(String input)
	  *to analyse the input
	  *and to determin the coefficient and the variable.
	  *call methods analyseCoefficient and analyseVariable
	  *@param input the expression of the term
	  *@return the simplest expression of the term
	  */
	public String analyse(String input)
	{
		//this method maby invoked by another method,so the vectors must clare and pos set to "0"
		variableName.clear();
		exponent.clear();
		pos = 0;

		String output = "";//to store the analysed data
		
		coefficient = analyseCoefficient(input);

		output += coefficient;
		
		//analyse variable
		if (pos <= input.length() - 1)
		{
			
			analyseVariable(input);

		}
		
		//set output
		for (int i = 0;i <= variableName.size() - 1 ;i++ )
		{
			
			output +=variableName.get(i);
			if (((Integer)exponent.get(i)).intValue() > 1)
			{
				output += "^" + exponent.get(i);
			}

		}

		return output;
	
	}

	/**
	  *analyse coefficient
	  */
	private long analyseCoefficient(String input)
	{
		
		int i = 0;//i to store the index of the first variable
		int j = 0;//j to store the index of the firse number
		
		//default coefficient is 1
		coefficient = 1;

		//deal the negative coefficient
		if (input.charAt(0) == '-')
		{
			coefficient *= -1;
			j++;
		}

		//find the first letter so to find the number
		while ((i < input.length()) && (!Character.isLetter(input.charAt(i))))
		{
			i++;
		}
		
		if (i >= 10)
		{
			pos = i;
			
			return 200000001;
		}
		
		//System.out.println(j + "" +i);
		if ((i - j) > 0)
		{
			coefficient *= (Integer.valueOf(input.substring(j,i))).intValue();
		}
		
		pos = i;
		
		return coefficient;
	}

	/**
	  *analyse variable
	  */
	private void analyseVariable(String input)
	{
		
		do
		{
			//the current variable's name
			Character tempName = new Character(input.charAt(pos));
			
			//the current variable's exponent
			int exp;
			if (pos < input.length() - 1)
			{
				exp = getExp(input);
			}
			else exp = 1;
		
			//judge if the term has already had the variablenanme add the current exponent to the original exponent
			//else add the name to the term's variablename
			if (variableName.contains(tempName))
			{
				
				int a = variableName.indexOf(tempName);//a to store the index of the object
				exp +=((Integer)exponent.get(a)).intValue();
				Integer tempInt = new Integer(exp);
				exponent.set(a,tempInt);
			}
			else 
			{
				variableName.add(tempName);
				Integer tempInt = new Integer(exp);
				exponent.add(tempInt);
			}
			
			//search the next variable
			do
			{
				pos++;
			}
			while ((pos < input.length()) && !Character.isLetter(input.charAt(pos)));
		}
		while (pos < input.length());
		
		//the variables have to be sort by the specified squence so that it will be easy to compare two terms
		sortVariable();
	}

	/**method sortVariable
	  *sort the variable by the variableName's dictionary sort
	  */
	private void sortVariable()
	{
		for (int i = variableName.size() - 1;i > 0;i-- )
		{
			for (int j = 0;j < i ;j++ )
			{
				if (((Character)variableName.get(j)).charValue() > ((Character)variableName.get(j + 1)).charValue())
				{
					change(j);
				}
			}
		}
	}

	/**method change
	  *chang the specified variableName and the corresponding exponent
	  *@param i the first variable's index
	  */
	private void change(int i)
	{
		char tempName = ((Character)variableName.get(i)).charValue();
		int tempExp = ((Integer)exponent.get(i)).intValue();
		
		variableName.setElementAt(new Character(((Character)variableName.get(i+1)).charValue()),i);
		exponent.setElementAt(new Integer(((Integer)exponent.get(i+1)).intValue()),i);

		variableName.setElementAt(new Character(tempName),i + 1);
		exponent.setElementAt(new Integer(tempExp),i + 1);

	}

	/**method getExp
	  */
	private int getExp(String input)
	{
		String exp = "";
		if (input.charAt(pos + 1) == '^')
		{
			int i = 2;
			//get the nubmber
			while ((pos + i < input.length()) && Character.isDigit(input.charAt(pos + i)))
			{
				exp += input.charAt(pos + i);
				i++;
			}

			return Integer.valueOf(exp).intValue();
		}
		else return 1;
	}
	
	/**method getCoefficient
	  *@return the value of the terms coefficient
	  */
	public long getCoefficient()
	{
		return coefficient;
	}
	/**method setCoefficient
	  *this method to modify the term's coefficient
	  *and it changes the s
	  *@param m the requied coefficient
	  */
	public void setCoefficient(long m)
	{
		if (m > 200000000)
		{
			m = 200000001;
		}

		coefficient = m;
		
		int i = 0;
		if (s.charAt(0) == '-')
		{
			i++;
		}
		while ((i < s.length()) && Character.isDigit(s.charAt(i)))
		{
			i++;
		}

		s = coefficient + s.substring(i,s.length());


	}

	/**method clone
	  *copy this term and return it
	  *@return the same Object as this
	  */
	public Object clone()
	{

		return new TermNode(this.s);
	}

    /**
	  *method toString
	  *return the polynomial type of the term
	  @return the terms simplest expression in String type
	  */
	public String toString()
	{
		
		if (variableName.isEmpty())
		{
			if (coefficient > 0)
			{
				return "+" + String.valueOf(coefficient);
			}
			else if (coefficient < 0)
			{
				return String.valueOf(coefficient);
			}
			else return "";
			
		}

		if (coefficient == 0)
		{
			return "";
		}

		if (coefficient == 1)
		{
			return "+" + s.substring(1,s.length());
		}

		if (coefficient > 1)
		{
			return "+" + s;
		}

		if (coefficient < -1)
		{
			return s;
		}

		if (coefficient == -1)
		{
			return "-" + s.substring(2,s.length());
		}

		return "";
		
	}

};