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PostgreSQL JDBC Driver JDBC4
There is a newer version: 42.7.3
/*-------------------------------------------------------------------------
*
* Copyright (c) 2003-2015 PostgreSQL Global Development Group
*
*
*-------------------------------------------------------------------------
*/

package org.postgresql.geometric;

import org.postgresql.util.GT;
import org.postgresql.util.PGobject;
import org.postgresql.util.PGtokenizer;
import org.postgresql.util.PSQLException;
import org.postgresql.util.PSQLState;

import java.io.Serializable;
import java.sql.SQLException;

/**
 * This implements a line represented by the linear equation Ax + By + C = 0
 *
 **/
public class PGline extends PGobject implements Serializable, Cloneable
{

    /**
     * Coefficient of x
     */
    public double a;

    /**
     * Coefficient of y
     */
    public double b;

    /**
     * Constant
     */
    public double c;

    /**
     * @param a coefficient of x
     * @param b coefficient of y
     * @param c constant
     */
    public PGline(double a, double b, double c) {
        this();
        this.a = a;
        this.b = b;
        this.c = c;
    }

    /**
     * @param x1 coordinate for first point on the line
     * @param y1 coordinate for first point on the line
     * @param x2 coordinate for second point on the line
     * @param y2 coordinate for second point on the line
     */
    public PGline(double x1, double y1, double x2, double y2)
    {
        this();
        if (x1 == x2) {
            a = -1;
            b = 0;
        } else {
            a = (y2 - y1) / (x2 - x1);
            b = -1;
        }
        c = y1 - a * x1;
    }

    /**
     * @param p1 first point on the line
     * @param p2 second point on the line
     */
    public PGline(PGpoint p1, PGpoint p2)
    {
        this(p1.x, p1.y, p2.x, p2.y);
    }

    /**
     * @param lseg Line segment which calls on this line.
     */
    public PGline(PGlseg lseg) {
        this(lseg.point[0], lseg.point[1]);
    }

    /**
     * @param s definition of the line in PostgreSQL's syntax.
     * @exception SQLException on conversion failure
     */
    public PGline(String s) throws SQLException
    {
        this();
        setValue(s);
    }

    /**
     * required by the driver
     */
    public PGline()
    {
        setType("line");
    }

    /**
     * @param s Definition of the line in PostgreSQL's syntax
     * @exception SQLException on conversion failure
     */
    public void setValue(String s) throws SQLException
    {
        if (s.trim().startsWith("{")) {
            PGtokenizer t = new PGtokenizer(PGtokenizer.removeCurlyBrace(s), ',');
            if (t.getSize() != 3)
                throw new PSQLException(GT.tr("Conversion to type {0} failed: {1}.", new Object[]{type,s}), PSQLState.DATA_TYPE_MISMATCH);
            a = Double.parseDouble(t.getToken(0));
            b = Double.parseDouble(t.getToken(1));
            c = Double.parseDouble(t.getToken(2));
        } else if (s.trim().startsWith("[")) {
            PGtokenizer t = new PGtokenizer(PGtokenizer.removeBox(s), ',');
            if (t.getSize() != 2)
                throw new PSQLException(GT.tr("Conversion to type {0} failed: {1}.", new Object[]{type,s}), PSQLState.DATA_TYPE_MISMATCH);
            PGpoint point1 = new PGpoint(t.getToken(0));
            PGpoint point2 = new PGpoint(t.getToken(1));
            a = point2.x - point1.x;
            b = point2.y - point1.y;
            c = point1.y;
        }
    }

    /**
     * @param obj Object to compare with
     * @return true if the two lines are identical
     */
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        if (!super.equals(obj)) return false;

        PGline pGline = (PGline)obj;

        return Double.compare(pGline.a, a) == 0 &&
                Double.compare(pGline.b, b) == 0 &&
                Double.compare(pGline.c, c) == 0;
    }

    public int hashCode() {
        int result = super.hashCode();
        long temp;
        temp = Double.doubleToLongBits(a);
        result = 31 * result + (int)(temp ^ (temp >>> 32));
        temp = Double.doubleToLongBits(b);
        result = 31 * result + (int)(temp ^ (temp >>> 32));
        temp = Double.doubleToLongBits(c);
        result = 31 * result + (int)(temp ^ (temp >>> 32));
        return result;
    }

    /**
     * @return the PGline in the syntax expected by org.postgresql
     */
    public String getValue()
    {
        return "{" + a + "," + b + "," + c + "}";
    }

}