第04章 - 几何对象模型详解

Coordinate c1 = new Coordinate(1, 2);
Coordinate c2 = new CoordinateXY(1, 2);

System.out.println(c1.equals(c2));       // false（类型不同，equals 严格）
System.out.println(c1.equals2D(c2));     // true（只比较 X/Y）

Coordinate c = new Coordinate(0, 0);
c.x = 10;          // 直接改字段
c.setY(20);        // 或通过 setter

Geometry g = factory.createPoint(c);
c.x = 999;         // 注意：这不会改变已创建的 Point！
System.out.println(g);  // POINT (0 0)

// 带 Z 的 WKT（旧 3D 格式或 EWKT）
Geometry g1 = reader.read("POINT Z (1 2 3)");
System.out.println(g1.getCoordinate().getZ());   // 3.0

// 带 M 的 WKT
Geometry g2 = reader.read("POINT M (1 2 100)");
System.out.println(g2.getCoordinate().getM());   // 100.0

// XYZM
Geometry g3 = reader.read("POINT ZM (1 2 3 100)");

// 一个经典的浮点陷阱
double x = 0.1 + 0.2;
System.out.println(x == 0.3);   // false

// JTS 的应对：① 精度模型（FIXED）② DD 类（双精度双倍）

// 默认工厂
GeometryFactory defaultGf = new GeometryFactory();
System.out.println(defaultGf.getCoordinateSequenceFactory().getClass().getSimpleName());
// CoordinateArraySequenceFactory

// 显式使用紧凑数组
GeometryFactory packedGf = new GeometryFactory(
    new PrecisionModel(),
    4326,
    PackedCoordinateSequenceFactory.DOUBLE_FACTORY);

Geometry g = reader.read("LINESTRING (0 0, 10 10, 20 0)");
CoordinateSequence seq = g.getCoordinates().length > 0
    ? ((LineString) g).getCoordinateSequence()
    : null;

for (int i = 0; i < seq.size(); i++) {
    System.out.printf("i=%d x=%.1f y=%.1f%n", i, seq.getX(i), seq.getY(i));
}

// 转成数组（会复制）
Coordinate[] arr = seq.toCoordinateArray();

Geometry g = reader.read("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))");
Envelope env = g.getEnvelopeInternal();
System.out.println(env);            // Envelope[0.0 : 10.0, 0.0 : 10.0]
System.out.println(env.getArea());  // 100.0（包络面积）
System.out.println(g.getArea());    // 100.0（几何面积，此处恰好相等）

Geometry circle = reader.read("POLYGON ((...))");  // 近似圆
System.out.println(circle.getEnvelopeInternal().getArea());  // 远大于实际面积

STRtree index = new STRtree();
for (Geometry g : geometries) {
    index.insert(g.getEnvelopeInternal(), g);
}
List<?> hits = index.query(queryGeo.getEnvelopeInternal());
// hits 只是候选，还要用 intersects/contains 精筛

Geometry gc = reader.read("GEOMETRYCOLLECTION (POINT (0 0), LINESTRING (1 1, 2 2))");
gc.union(somePolygon);   // 抛 IllegalArgumentException？

// 错误
if (g instanceof GeometryCollection) { ... }   // MultiPolygon 也会命中

// 正确
if (g.isGeometryCollection()) { ... }           // 仅纯 GeometryCollection
// 或
if (g.getGeometryType().equals("GeometryCollection")) { ... }

// 对 Point 返回 1，对 MultiPolygon 返回成员数
for (int i = 0; i < g.getNumGeometries(); i++) {
    Geometry part = g.getGeometryN(i);
    System.out.println(part.getGeometryType() + " area=" + part.getArea());
}

// 1. 默认：FLOATING 精度、SRID=0、CoordinateArraySequence
GeometryFactory gf1 = new GeometryFactory();

// 2. 指定 SRID
GeometryFactory gf2 = new GeometryFactory(new PrecisionModel(), 4326);

// 3. 指定 SRID + 序列工厂
GeometryFactory gf3 = new GeometryFactory(
    new PrecisionModel(), 4326, PackedCoordinateSequenceFactory.DOUBLE_FACTORY);

// 4. 指定精度模型
GeometryFactory gf4 = new GeometryFactory(new PrecisionModel(1000)); // 保留 3 位小数

// 正确：闭合
Polygon ok = gf.createPolygon(new Coordinate[] {
    new Coordinate(0, 0), new Coordinate(10, 0),
    new Coordinate(10, 10), new Coordinate(0, 10),
    new Coordinate(0, 0)          // 必须回到起点
});

// 错误：未闭合 → IllegalArgumentException
try {
    gf.createPolygon(new Coordinate[] {
        new Coordinate(0, 0), new Coordinate(10, 0),
        new Coordinate(10, 10), new Coordinate(0, 10)
    });
} catch (IllegalArgumentException e) {
    System.out.println("环未闭合: " + e.getMessage());
}

Point emptyPoint = gf.createPoint();                       // POINT EMPTY
LineString emptyLine = gf.createLineString();              // LINESTRING EMPTY
Polygon emptyPolygon = gf.createPolygon();                 // POLYGON EMPTY
Geometry emptyOfDim2 = gf.createEmpty(2);                  // POLYGON EMPTY

GeometryFactory gf4326 = new GeometryFactory(new PrecisionModel(), 4326);
Geometry a = gf4326.createPoint(new Coordinate(0, 0));
Geometry b = gf4326.createPoint(new Coordinate(1, 1));

Geometry union = a.union(b);
System.out.println(union.getSRID());   // 4326（继承自 a）

System.out.println(g.getDimension());          // 0/1/2
System.out.println(g.getBoundaryDimension());  // 边界的维度
System.out.println(g.hasDimension(1));         // 1.20+ 新增

Point p = gf.createPoint(new Coordinate(0, 0));
System.out.println(p.getBoundary());              // GEOMETRYCOLLECTION EMPTY（点无边界的“几何”）

LineString line = (LineString) reader.read("LINESTRING (0 0, 10 0)");
System.out.println(line.getBoundary());           // MULTIPOINT ((0 0), (10 0))

Polygon poly = (Polygon) reader.read("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))");
System.out.println(poly.getBoundary());           // LINEARRING (0 0, 10 0, 10 10, 0 10, 0 0)

// 有洞的多边形
Polygon withHole = (Polygon) reader.read(
    "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (2 2, 4 2, 4 4, 2 4, 2 2))");
System.out.println(withHole.getBoundary());       // MULTILINESTRING (...)

import org.locationtech.jts.algorithm.PointLocator;
import org.locationtech.jts.geom.Location;

PointLocator locator = new PointLocator();
Location loc = locator.locate(new Coordinate(0, 0), polygon);
System.out.println(loc == Location.BOUNDARY ? "边界上" : "不是边界");

Geometry empty = gf.createPolygon();   // 非 null
System.out.println(empty.isEmpty());   // true
System.out.println(empty.getNumPoints()); // 0
System.out.println(empty.getGeometryType()); // Polygon
System.out.println(empty.getEnvelopeInternal().isNull()); // true

Polygon p = (Polygon) reader.read(
    "POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0))");  // 逆时针？
System.out.println(p.normalize());   // 规整后的 WKT

// 判断环的方向（1.19+ 提供了 Orientation.isCCW）
import org.locationtech.jts.algorithm.Orientation;
boolean ccw = Orientation.isCCW(polygon.getExteriorRing().getCoordinates());

Geometry g = reader.read("LINESTRING (0 0, 10 10)");
Geometry r = g.reverse();
System.out.println(r);   // LINESTRING (10 10, 0 0)

Geometry n = g.norm();   // 等价于 copy + normalize

Polygon poly = (Polygon) reader.read(
    "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), " +
    "         (2 2, 4 2, 4 4, 2 4, 2 2), " +
    "         (6 6, 8 6, 8 8, 6 8, 6 6))");

System.out.println("外环点数: " + poly.getExteriorRing().getNumPoints());   // 5
System.out.println("内环数量: " + poly.getNumInteriorRing());                // 2
System.out.println("总点数: " + poly.getNumPoints());                        // 15
System.out.println("面积: " + poly.getArea());                               // 100 - 4 - 4 = 92

// 遍历所有环
for (int i = 0; i < poly.getNumInteriorRing(); i++) {
    LinearRing hole = poly.getInteriorRingN(i);
    System.out.println("内环 " + i + " 面积: " + hole.getArea());
}

// 无效：孔在外部
Geometry invalid = reader.read(
    "POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (20 20, 22 20, 22 22, 20 22, 20 20))");

IsValidOp validOp = new IsValidOp(invalid);
System.out.println(validOp.isValid());          // false
System.out.println(validOp.getValidationError()); // 错误信息

// 面积计算示意
Polygon rect = (Polygon) reader.read("POLYGON ((0 0, 10 0, 10 5, 0 5, 0 0))");
System.out.println(rect.getArea());   // 50.0

// 用 buffer(-x) 做“内缩”时，孔可能被消除，环数量会变化
Polygon shrunk = (Polygon) rect.buffer(-1);
System.out.println(shrunk.getNumInteriorRing());

LinearRing shell = gf.createLinearRing(new Coordinate[] {
    new Coordinate(0, 0), new Coordinate(10, 0),
    new Coordinate(10, 10), new Coordinate(0, 10),
    new Coordinate(0, 0)
});
LinearRing hole = gf.createLinearRing(new Coordinate[] {
    new Coordinate(2, 2), new Coordinate(4, 2),
    new Coordinate(4, 4), new Coordinate(2, 4),
    new Coordinate(2, 2)
});

Polygon withHole = gf.createPolygon(shell, new LinearRing[] { hole });
System.out.println(withHole.getArea());   // 100 - 4 = 96

// 合法：MultiPolygon 两个不相交的面
Geometry mp = reader.read("MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)), ((2 2, 3 2, 3 3, 2 3, 2 2)))");

// 有效性问题：MultiPolygon 成员重叠
Geometry overlap = reader.read("MULTIPOLYGON (((0 0, 2 0, 2 2, 0 2, 0 0)), ((1 1, 3 1, 3 3, 1 3, 1 1)))");
new IsValidOp(overlap).isValid();   // false（成员重叠）

// 不要用 instanceof 判断“是不是集合”
if (g instanceof GeometryCollection) { ... }        // MultiPolygon 也会命中

// 用 isGeometryCollection()
if (g.isGeometryCollection()) { ... }                // 仅纯 GeometryCollection

// 或者用几何类型字符串
switch (g.getGeometryType()) {
    case "Point": ...
    case "MultiPolygon": ...
    case "GeometryCollection": ...
    default: ...
}

import org.locationtech.jts.geom.GeometryCollectionIterator;

// 方式一：递归遍历
for (java.util.Iterator<?> it = new GeometryCollectionIterator(gc); it.hasNext(); ) {
    Geometry part = (Geometry) it.next();
    if (!(part instanceof GeometryCollection)) {
        System.out.println(part.getGeometryType());
    }
}

// 方式二：用 GeometryExtracter 按类型提取
import org.locationtech.jts.geom.util.LineStringExtracter;
Geometry lines = LineStringExtracter.getGeometry(gc);

GeometryFactory gf4326 = new GeometryFactory(new PrecisionModel(), 4326);
Geometry p = gf4326.createPoint(new Coordinate(116.4, 39.9));
System.out.println(p.getSRID());    // 4326

// 运算结果继承输入工厂
Geometry buffered = p.buffer(0.01);
System.out.println(buffered.getSRID());  // 4326

Geometry a = new GeometryFactory(new PrecisionModel(), 4326).createPoint(new Coordinate(0,0));
Geometry b = new GeometryFactory(new PrecisionModel(), 3857).createPoint(new Coordinate(1,1));
System.out.println(a.union(b).getSRID());   // 4326（a 的）

// 1) 给从 WKT 读入的几何补上 SRID
Geometry g = reader.read("POINT (116.4 39.9)");
g.setSRID(4326);

// 2) 批量设置
for (Geometry item : collection) {
    item.setSRID(4326);
}

// 3) 从旧几何复制 SRID
Geometry copy = other.copy();
copy.setSRID(source.getSRID());

Geometry g = reader.read("POINT (1 2)");
g.setUserData(Map.of("id", 1001, "name", "采样点"));
System.out.println(g.getUserData());

// 运算结果是否继承 userData？默认不继承（新对象），需要自己处理

// 不推荐：每次都 new GeometryFactory
for (int i = 0; i < 100000; i++) {
    GeometryFactory f = new GeometryFactory();     // 浪费
    f.createPoint(new Coordinate(i, i));           // 每次 new Coordinate
}

// 推荐：工厂复用 + 坐标复用
GeometryFactory f = new GeometryFactory();
Coordinate c = new Coordinate();
for (int i = 0; i < 100000; i++) {
    c.x = i; c.y = i;
    Geometry p = f.createPoint(c);                 // 工厂内部复制，c 可复用
}

double[] xy = new double[2000];
for (int i = 0; i < 1000; i++) {
    xy[2*i] = i;
    xy[2*i+1] = i * 2;
}
CoordinateSequence seq = PackedCoordinateSequenceFactory.DOUBLE_FACTORY.create(xy, 2);
LineString line = packedGf.createLineString(seq);

Geometry copy1 = g.copy();     // 推荐：返回独立副本
Geometry copy2 = g.clone();    // 旧 API，语义类似

// 要修改又不想影响原对象：
Geometry modified = g.copy();
modified.normalize();          // 原地修改副本