## com.vividsolutions.jts.geom
Class LineSegment

    java.lang.Object
      com.vividsolutions.jts.geom.LineSegment

All Implemented Interfaces:
  java.lang.Comparable, java.io.Serializable

Direct Known Subclasses:
  TaggedLineSegment

public class LineSegment
extends java.lang.Object
implements java.lang.Comparable, java.io.Serializable

Represents a line segment defined by two `Coordinate`s. Provides methods to compute various geometric properties and relationships of line segments.

This class is designed to be easily mutable (to the extent of having its contained points public). This supports a common pattern of reusing a single LineSegment object as a way of computing segment properties on the segments defined by arrays or lists of `Coordinate`s.

Version:
  1.7
See Also:
  Serialized Form

Field Summary
`Coordinate` `p0`
`Coordinate` `p1`

Constructor Summary
`LineSegment()`
`LineSegment(Coordinate p0, Coordinate p1)`
`LineSegment(double x0, double y0, double x1, double y1)`
`LineSegment(LineSegment ls)`

Method Summary
`double` `angle()` Computes the angle that the vector defined by this segment makes with the X-axis.
`Coordinate` `closestPoint(Coordinate p)` Computes the closest point on this line segment to another point.
`Coordinate[]` `closestPoints(LineSegment line)` Computes the closest points on two line segments.
`int` `compareTo(java.lang.Object o)` Compares this object with the specified object for order.
`double` `distance(Coordinate p)` Computes the distance between this line segment and a given point.
`double` `distance(LineSegment ls)` Computes the distance between this line segment and another segment.
`double` `distancePerpendicular(Coordinate p)` Computes the perpendicular distance between the (infinite) line defined by this line segment and a point.
`boolean` `equals(java.lang.Object o)` Returns `true` if `other` has the same values for its points.
`boolean` `equalsTopo(LineSegment other)` Returns `true` if `other` is topologically equal to this LineSegment (e.g.
`Coordinate` `getCoordinate(int i)`
`double` `getLength()` Computes the length of the line segment.
`int` `hashCode()` Gets a hashcode for this object.
`Coordinate` `intersection(LineSegment line)` Computes an intersection point between two segments, if there is one.
`boolean` `isHorizontal()` Tests whether the segment is horizontal.
`boolean` `isVertical()` Tests whether the segment is vertical.
`Coordinate` `lineIntersection(LineSegment line)` Computes the intersection point of the lines defined by two segments, if there is one.
`Coordinate` `midPoint()` Computes the midpoint of the segment
`void` `normalize()` Puts the line segment into a normalized form.
`int` `orientationIndex(Coordinate p)` Determines the orientation index of a `Coordinate` relative to this segment.
`int` `orientationIndex(LineSegment seg)` Determines the orientation of a LineSegment relative to this segment.
`Coordinate` `pointAlong(double segmentLengthFraction)` Computes the `Coordinate` that lies a given fraction along the line defined by this segment.
`Coordinate` `pointAlongOffset(double segmentLengthFraction, double offsetDistance)` Computes the `Coordinate` that lies a given fraction along the line defined by this segment and offset from the segment by a given distance.
`Coordinate` `project(Coordinate p)` Compute the projection of a point onto the line determined by this line segment.
`LineSegment` `project(LineSegment seg)` Project a line segment onto this line segment and return the resulting line segment.
`double` `projectionFactor(Coordinate p)` Computes the Projection Factor for the projection of the point p onto this LineSegment.
`void` `reverse()` Reverses the direction of the line segment.
`double` `segmentFraction(Coordinate inputPt)` Computes the fraction of distance (in `[0.0, 1.0]`) that the projection of a point occurs along this line segment.
`void` `setCoordinates(Coordinate p0, Coordinate p1)`
`void` `setCoordinates(LineSegment ls)`
`LineString` `toGeometry(GeometryFactory geomFactory)` Creates a LineString with the same coordinates as this segment
`java.lang.String` `toString()`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### p0

    public Coordinate p0

### p1

    public Coordinate p1

Constructor Detail

### LineSegment

    public LineSegment(Coordinate p0,
                       Coordinate p1)

### LineSegment

    public LineSegment(double x0,
                       double y0,
                       double x1,
                       double y1)

### LineSegment

    public LineSegment(LineSegment ls)

### LineSegment

    public LineSegment()

Method Detail

### getCoordinate

    public Coordinate getCoordinate(int i)

### setCoordinates

    public void setCoordinates(LineSegment ls)

### setCoordinates

    public void setCoordinates(Coordinate p0,
                               Coordinate p1)

### getLength

    public double getLength()

  Computes the length of the line segment.

  Returns:
    the length of the line segment

### isHorizontal

    public boolean isHorizontal()

  Tests whether the segment is horizontal.

  Returns:
    `true` if the segment is horizontal

### isVertical

    public boolean isVertical()

  Tests whether the segment is vertical.

  Returns:
    `true` if the segment is vertical

### orientationIndex

    public int orientationIndex(LineSegment seg)

  Determines the orientation of a LineSegment relative to this segment. The concept of orientation is specified as follows: Given two line segments A and L, <ul
  - A is to the left of a segment L if A lies wholly in the closed half-plane lying to the left of L
  - A is to the right of a segment L if A lies wholly in the closed half-plane lying to the right of L
  - otherwise, A has indeterminate orientation relative to L. This happens if A is collinear with L or if A crosses the line determined by L.

  Parameters:
    `seg` - the LineSegment to compare
  Returns:
    1 if `seg` is to the left of this segment

### orientationIndex

    public int orientationIndex(Coordinate p)

  Determines the orientation index of a `Coordinate` relative to this segment. The orientation index is as defined in `CGAlgorithms.computeOrientation(com.vividsolutions.jts.geom.Coordinate, com.vividsolutions.jts.geom.Coordinate, com.vividsolutions.jts.geom.Coordinate)`.

  Returns:
    1 if `p` is to the left of this segment
  See Also:
    `CGAlgorithms.computeOrientation(Coordinate, Coordinate, Coordinate)`

### reverse

    public void reverse()

  Reverses the direction of the line segment.

### normalize

    public void normalize()

  Puts the line segment into a normalized form. This is useful for using line segments in maps and indexes when topological equality rather than exact equality is desired. A segment in normalized form has the first point smaller than the second (according to the standard ordering on `Coordinate`).

### angle

    public double angle()

  Computes the angle that the vector defined by this segment makes with the X-axis. The angle will be in the range [ -PI, PI ] radians.

  Returns:
    the angle this segment makes with the X-axis (in radians)

### midPoint

    public Coordinate midPoint()

  Computes the midpoint of the segment

  Returns:
    the midpoint of the segment

### distance

    public double distance(LineSegment ls)

  Computes the distance between this line segment and another segment.

  Returns:
    the distance to the other segment

### distance

    public double distance(Coordinate p)

  Computes the distance between this line segment and a given point.

  Returns:
    the distance from this segment to the given point

### distancePerpendicular

    public double distancePerpendicular(Coordinate p)

  Computes the perpendicular distance between the (infinite) line defined by this line segment and a point.

  Returns:
    the perpendicular distance between the defined line and the given point

### pointAlong

    public Coordinate pointAlong(double segmentLengthFraction)

  Computes the `Coordinate` that lies a given fraction along the line defined by this segment. A fraction of `0.0` returns the start point of the segment; a fraction of `1.0` returns the end point of the segment. If the fraction is < 0.0 or > 1.0 the point returned will lie before the start or beyond the end of the segment.

  Parameters:
    `segmentLengthFraction` - the fraction of the segment length along the line
  Returns:
    the point at that distance

### pointAlongOffset

    public Coordinate pointAlongOffset(double segmentLengthFraction,
                                       double offsetDistance)

  Computes the `Coordinate` that lies a given fraction along the line defined by this segment and offset from the segment by a given distance. A fraction of `0.0` offsets from the start point of the segment; a fraction of `1.0` offsets from the end point of the segment. The computed point is offset to the left of the line if the offset distance is positive, to the right if negative.

  Parameters:
    `segmentLengthFraction` - the fraction of the segment length along the line
    `offsetDistance` - the distance the point is offset from the segment (positive is to the left, negative is to the right)
  Returns:
    the point at that distance and offset
  Throws:
    `java.lang.IllegalStateException` - if the segment has zero length

### projectionFactor

    public double projectionFactor(Coordinate p)

  Computes the Projection Factor for the projection of the point p onto this LineSegment. The Projection Factor is the constant r by which the vector for this segment must be multiplied to equal the vector for the projection of `p on the line defined by this segment.

  The projection factor returned will be in the range `(-inf, +inf)`.

  `
  Parameters:
    `p` - the point to compute the factor for
  Returns:
    the projection factor for the point

### segmentFraction

    public double segmentFraction(Coordinate inputPt)

  Computes the fraction of distance (in `[0.0, 1.0]`) that the projection of a point occurs along this line segment. If the point is beyond either ends of the line segment, the closest fractional value (`0.0` or `1.0`) is returned.

  Essentially, this is the `projectionFactor(com.vividsolutions.jts.geom.Coordinate)` clamped to the range `[0.0, 1.0]`.

  Parameters:
    `inputPt` - the point
  Returns:
    the fraction along the line segment the projection of the point occurs

### project

    public Coordinate project(Coordinate p)

  Compute the projection of a point onto the line determined by this line segment.

  Note that the projected point may lie outside the line segment. If this is the case, the projection factor will lie outside the range [0.0, 1.0].

### project

    public LineSegment project(LineSegment seg)

  Project a line segment onto this line segment and return the resulting line segment. The returned line segment will be a subset of the target line line segment. This subset may be null, if the segments are oriented in such a way that there is no projection.

  Note that the returned line may have zero length (i.e. the same endpoints). This can happen for instance if the lines are perpendicular to one another.

  Parameters:
    `seg` - the line segment to project
  Returns:
    the projected line segment, or `null` if there is no overlap

### closestPoint

    public Coordinate closestPoint(Coordinate p)

  Computes the closest point on this line segment to another point.

  Parameters:
    `p` - the point to find the closest point to
  Returns:
    a Coordinate which is the closest point on the line segment to the point p

### closestPoints

    public Coordinate[] closestPoints(LineSegment line)

  Computes the closest points on two line segments.

  Returns:
    a pair of Coordinates which are the closest points on the line segments

### intersection

    public Coordinate intersection(LineSegment line)

  Computes an intersection point between two segments, if there is one. There may be 0, 1 or many intersection points between two segments. If there are 0, null is returned. If there is 1 or more, a single one is returned (chosen at the discretion of the algorithm). If more information is required about the details of the intersection, the `RobustLineIntersector` class should be used.

  Parameters:
    `line` - a line segment
  Returns:
    an intersection point, or `null` if there is none
  See Also:
    `RobustLineIntersector`

### lineIntersection

    public Coordinate lineIntersection(LineSegment line)

  Computes the intersection point of the lines defined by two segments, if there is one. There may be 0, 1 or an infinite number of intersection points between two lines. If there is a unique intersection point, it is returned. Otherwise, `null` is returned. If more information is required about the details of the intersection, the `RobustLineIntersector` class should be used.

  Parameters:
    `line` - a line segment defining a straight line
  Returns:
    an intersection point, or `null` if there is none or an infinite number
  See Also:
    `RobustLineIntersector`

### toGeometry

    public LineString toGeometry(GeometryFactory geomFactory)

  Creates a LineString with the same coordinates as this segment

  Parameters:
    `geomFactory` - the geometery factory to use
  Returns:
    a LineString with the same geometry as this segment

### equals

    public boolean equals(java.lang.Object o)

  Returns `true` if `other` has the same values for its points.

  Returns:
    `true` if `other` is a `LineSegment` with the same values for the x and y ordinates.

### hashCode

    public int hashCode()

  Gets a hashcode for this object.

  Returns:
    a hashcode for this object

### compareTo

    public int compareTo(java.lang.Object o)

  Compares this object with the specified object for order. Uses the standard lexicographic ordering for the points in the LineSegment.

  Specified by:
    `compareTo` in interface `java.lang.Comparable`
  Parameters:
    `o` - the `LineSegment` with which this `LineSegment` is being compared
  Returns:
    a negative integer, zero, or a positive integer as this `LineSegment` is less than, equal to, or greater than the specified `LineSegment`

### equalsTopo

    public boolean equalsTopo(LineSegment other)

  Returns `true` if `other` is topologically equal to this LineSegment (e.g. irrespective of orientation).

  Parameters:
    `other` - a `LineSegment` with which to do the comparison.
  Returns:
    `true` if `other` is a `LineSegment` with the same values for the x and y ordinates.

### toString

    public java.lang.String toString()