constraint.java

This is my implementation for linear programming

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package ro.simplex;

import java.util.ArrayList;
import ro.utils.Fraction;

/**
 *
 * @author Doan Chien Thang
 */
public class Constraint {
    private int type;
    private ArrayList<Fraction> coefs;
    private ArrayList<Variable> vars;
    private Fraction value;

    public Constraint() {
        this.coefs = new ArrayList<Fraction>();
        this.vars = new ArrayList<Variable>();
        this.value = null;
    }

    public Constraint(int type, ArrayList<Fraction> coefficients,
            ArrayList<Variable> variables, Fraction value) {
        this.type = type;
        this.coefs = coefficients;
        this.vars = variables;
        this.value = value;
    }

    public ArrayList<Fraction> getCoefs() {
        return this.coefs;
    }

    public void setVars(ArrayList<Variable> vars) {
        this.vars = vars;
    }

    public ArrayList<Variable> getVars() {
        return this.vars;
    }

    public void setValue(Fraction value) {
        this.value = value;
    }

    public Fraction getValue() {
        return this.value;
    }

    public int getType() {
        return this.type;
    }

    public VariableConstraint getVarConstraint(Variable leftVar) {
        ArrayList<Variable> rightVars = new ArrayList<Variable>();
        ArrayList<Fraction> newCoefs = new ArrayList<Fraction>();
        Fraction coef = new Fraction(1);
        for (int i = 0; i < coefs.size(); i++)
            if (!vars.get(i).equals(leftVar)) {
                rightVars.add(vars.get(i));
                newCoefs.add(coefs.get(i).getOpposite());
            } else
                coef = coefs.get(i);
        for (int i = 0; i < newCoefs.size(); i++)
            Fraction.divide(newCoefs.get(i), coef);
        return new VariableConstraint(leftVar, rightVars, newCoefs,
                Fraction.divide(value, coef));
    }

    @Override
    public String toString() {
        if (coefs.size() == 0)
            return "";
        String result = "&nbsp;&nbsp;&nbsp;&nbsp;";
        if (!coefs.get(0).absolute().equals(new Fraction(1)))
            result += coefs.get(0).toString();
        if (coefs.get(0).equals(new Fraction(-1)))
            result += "-";
        result += vars.get(0).toString();
        for (int i = 1; i < vars.size(); i++) {
            if (coefs.get(i).isNegative()) {
                result += "  -  ";
                if (!coefs.get(i).absolute().equals(new Fraction(1)))
                     result += coefs.get(i).absolute().toString();
                result += vars.get(i).toString();
            }
            else if (!coefs.get(i).equals(new Fraction(0))) {
                result += "  +  ";
                if (!coefs.get(i).absolute().equals(new Fraction(1)))
                    result += coefs.get(i).absolute().toString();
                result += vars.get(i).toString();
            }
        }
        switch (type) {
            case ConstraintTypes.EQUAL_TO:
                result += " = " + value.toString();
                break;
            case ConstraintTypes.GREATER_THAN:
                result += " &ge; " + value.toString();
                break;
            case ConstraintTypes.LESS_THAN:
                result += " &le; " + value.toString();
                break;
            default:
                break;
        }
        return result + "<br />";
    }
}