Java tutorial
/* * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.awt; import java.awt.geom.AffineTransform; import java.awt.geom.PathIterator; import java.awt.geom.Point2D; import java.awt.geom.Rectangle2D; /** * The {@code Shape} interface provides definitions for objects * that represent some form of geometric shape. The {@code Shape} * is described by a {@link PathIterator} object, which can express the * outline of the {@code Shape} as well as a rule for determining * how the outline divides the 2D plane into interior and exterior * points. Each {@code Shape} object provides callbacks to get the * bounding box of the geometry, determine whether points or * rectangles lie partly or entirely within the interior * of the {@code Shape}, and retrieve a {@code PathIterator} * object that describes the trajectory path of the {@code Shape} * outline. * <p> * <a id="def_insideness"><b>Definition of insideness:</b></a> * A point is considered to lie inside a * {@code Shape} if and only if: * <ul> * <li> it lies completely * inside the {@code Shape} boundary <i>or</i> * <li> * it lies exactly on the {@code Shape} boundary <i>and</i> the * space immediately adjacent to the * point in the increasing {@code X} direction is * entirely inside the boundary <i>or</i> * <li> * it lies exactly on a horizontal boundary segment <b>and</b> the * space immediately adjacent to the point in the * increasing {@code Y} direction is inside the boundary. * </ul> * <p>The {@code contains} and {@code intersects} methods * consider the interior of a {@code Shape} to be the area it * encloses as if it were filled. This means that these methods * consider * unclosed shapes to be implicitly closed for the purpose of * determining if a shape contains or intersects a rectangle or if a * shape contains a point. * * @see java.awt.geom.PathIterator * @see java.awt.geom.AffineTransform * @see java.awt.geom.FlatteningPathIterator * @see java.awt.geom.GeneralPath * * @author Jim Graham * @since 1.2 */ public interface Shape { /** * Returns an integer {@link Rectangle} that completely encloses the * {@code Shape}. Note that there is no guarantee that the * returned {@code Rectangle} is the smallest bounding box that * encloses the {@code Shape}, only that the {@code Shape} * lies entirely within the indicated {@code Rectangle}. The * returned {@code Rectangle} might also fail to completely * enclose the {@code Shape} if the {@code Shape} overflows * the limited range of the integer data type. The * {@code getBounds2D} method generally returns a * tighter bounding box due to its greater flexibility in * representation. * * <p> * Note that the * <a href="{@docRoot}/java.desktop/java/awt/Shape.html#def_insideness"> * definition of insideness</a> can lead to situations where points * on the defining outline of the {@code shape} may not be considered * contained in the returned {@code bounds} object, but only in cases * where those points are also not considered contained in the original * {@code shape}. * </p> * <p> * If a {@code point} is inside the {@code shape} according to the * {@link #contains(double x, double y) contains(point)} method, then * it must be inside the returned {@code Rectangle} bounds object * according to the {@link #contains(double x, double y) contains(point)} * method of the {@code bounds}. Specifically: * </p> * <p> * {@code shape.contains(x,y)} requires {@code bounds.contains(x,y)} * </p> * <p> * If a {@code point} is not inside the {@code shape}, then it might * still be contained in the {@code bounds} object: * </p> * <p> * {@code bounds.contains(x,y)} does not imply {@code shape.contains(x,y)} * </p> * @return an integer {@code Rectangle} that completely encloses * the {@code Shape}. * @see #getBounds2D * @since 1.2 */ public Rectangle getBounds(); /** * Returns a high precision and more accurate bounding box of * the {@code Shape} than the {@code getBounds} method. * Note that there is no guarantee that the returned * {@link Rectangle2D} is the smallest bounding box that encloses * the {@code Shape}, only that the {@code Shape} lies * entirely within the indicated {@code Rectangle2D}. The * bounding box returned by this method is usually tighter than that * returned by the {@code getBounds} method and never fails due * to overflow problems since the return value can be an instance of * the {@code Rectangle2D} that uses double precision values to * store the dimensions. * * <p> * Note that the * <a href="{@docRoot}/java.desktop/java/awt/Shape.html#def_insideness"> * definition of insideness</a> can lead to situations where points * on the defining outline of the {@code shape} may not be considered * contained in the returned {@code bounds} object, but only in cases * where those points are also not considered contained in the original * {@code shape}. * </p> * <p> * If a {@code point} is inside the {@code shape} according to the * {@link #contains(Point2D p) contains(point)} method, then it must * be inside the returned {@code Rectangle2D} bounds object according * to the {@link #contains(Point2D p) contains(point)} method of the * {@code bounds}. Specifically: * </p> * <p> * {@code shape.contains(p)} requires {@code bounds.contains(p)} * </p> * <p> * If a {@code point} is not inside the {@code shape}, then it might * still be contained in the {@code bounds} object: * </p> * <p> * {@code bounds.contains(p)} does not imply {@code shape.contains(p)} * </p> * @return an instance of {@code Rectangle2D} that is a * high-precision bounding box of the {@code Shape}. * @see #getBounds * @since 1.2 */ public Rectangle2D getBounds2D(); /** * Tests if the specified coordinates are inside the boundary of the * {@code Shape}, as described by the * <a href="{@docRoot}/java.desktop/java/awt/Shape.html#def_insideness"> * definition of insideness</a>. * @param x the specified X coordinate to be tested * @param y the specified Y coordinate to be tested * @return {@code true} if the specified coordinates are inside * the {@code Shape} boundary; {@code false} * otherwise. * @since 1.2 */ public boolean contains(double x, double y); /** * Tests if a specified {@link Point2D} is inside the boundary * of the {@code Shape}, as described by the * <a href="{@docRoot}/java.desktop/java/awt/Shape.html#def_insideness"> * definition of insideness</a>. * @param p the specified {@code Point2D} to be tested * @return {@code true} if the specified {@code Point2D} is * inside the boundary of the {@code Shape}; * {@code false} otherwise. * @since 1.2 */ public boolean contains(Point2D p); /** * Tests if the interior of the {@code Shape} intersects the * interior of a specified rectangular area. * The rectangular area is considered to intersect the {@code Shape} * if any point is contained in both the interior of the * {@code Shape} and the specified rectangular area. * <p> * The {@code Shape.intersects()} method allows a {@code Shape} * implementation to conservatively return {@code true} when: * <ul> * <li> * there is a high probability that the rectangular area and the * {@code Shape} intersect, but * <li> * the calculations to accurately determine this intersection * are prohibitively expensive. * </ul> * This means that for some {@code Shapes} this method might * return {@code true} even though the rectangular area does not * intersect the {@code Shape}. * The {@link java.awt.geom.Area Area} class performs * more accurate computations of geometric intersection than most * {@code Shape} objects and therefore can be used if a more precise * answer is required. * * @param x the X coordinate of the upper-left corner * of the specified rectangular area * @param y the Y coordinate of the upper-left corner * of the specified rectangular area * @param w the width of the specified rectangular area * @param h the height of the specified rectangular area * @return {@code true} if the interior of the {@code Shape} and * the interior of the rectangular area intersect, or are * both highly likely to intersect and intersection calculations * would be too expensive to perform; {@code false} otherwise. * @see java.awt.geom.Area * @since 1.2 */ public boolean intersects(double x, double y, double w, double h); /** * Tests if the interior of the {@code Shape} intersects the * interior of a specified {@code Rectangle2D}. * The {@code Shape.intersects()} method allows a {@code Shape} * implementation to conservatively return {@code true} when: * <ul> * <li> * there is a high probability that the {@code Rectangle2D} and the * {@code Shape} intersect, but * <li> * the calculations to accurately determine this intersection * are prohibitively expensive. * </ul> * This means that for some {@code Shapes} this method might * return {@code true} even though the {@code Rectangle2D} does not * intersect the {@code Shape}. * The {@link java.awt.geom.Area Area} class performs * more accurate computations of geometric intersection than most * {@code Shape} objects and therefore can be used if a more precise * answer is required. * * @param r the specified {@code Rectangle2D} * @return {@code true} if the interior of the {@code Shape} and * the interior of the specified {@code Rectangle2D} * intersect, or are both highly likely to intersect and intersection * calculations would be too expensive to perform; {@code false} * otherwise. * @see #intersects(double, double, double, double) * @since 1.2 */ public boolean intersects(Rectangle2D r); /** * Tests if the interior of the {@code Shape} entirely contains * the specified rectangular area. All coordinates that lie inside * the rectangular area must lie within the {@code Shape} for the * entire rectangular area to be considered contained within the * {@code Shape}. * <p> * The {@code Shape.contains()} method allows a {@code Shape} * implementation to conservatively return {@code false} when: * <ul> * <li> * the {@code intersect} method returns {@code true} and * <li> * the calculations to determine whether or not the * {@code Shape} entirely contains the rectangular area are * prohibitively expensive. * </ul> * This means that for some {@code Shapes} this method might * return {@code false} even though the {@code Shape} contains * the rectangular area. * The {@link java.awt.geom.Area Area} class performs * more accurate geometric computations than most * {@code Shape} objects and therefore can be used if a more precise * answer is required. * * @param x the X coordinate of the upper-left corner * of the specified rectangular area * @param y the Y coordinate of the upper-left corner * of the specified rectangular area * @param w the width of the specified rectangular area * @param h the height of the specified rectangular area * @return {@code true} if the interior of the {@code Shape} * entirely contains the specified rectangular area; * {@code false} otherwise or, if the {@code Shape} * contains the rectangular area and the * {@code intersects} method returns {@code true} * and the containment calculations would be too expensive to * perform. * @see java.awt.geom.Area * @see #intersects * @since 1.2 */ public boolean contains(double x, double y, double w, double h); /** * Tests if the interior of the {@code Shape} entirely contains the * specified {@code Rectangle2D}. * The {@code Shape.contains()} method allows a {@code Shape} * implementation to conservatively return {@code false} when: * <ul> * <li> * the {@code intersect} method returns {@code true} and * <li> * the calculations to determine whether or not the * {@code Shape} entirely contains the {@code Rectangle2D} * are prohibitively expensive. * </ul> * This means that for some {@code Shapes} this method might * return {@code false} even though the {@code Shape} contains * the {@code Rectangle2D}. * The {@link java.awt.geom.Area Area} class performs * more accurate geometric computations than most * {@code Shape} objects and therefore can be used if a more precise * answer is required. * * @param r The specified {@code Rectangle2D} * @return {@code true} if the interior of the {@code Shape} * entirely contains the {@code Rectangle2D}; * {@code false} otherwise or, if the {@code Shape} * contains the {@code Rectangle2D} and the * {@code intersects} method returns {@code true} * and the containment calculations would be too expensive to * perform. * @see #contains(double, double, double, double) * @since 1.2 */ public boolean contains(Rectangle2D r); /** * Returns an iterator object that iterates along the * {@code Shape} boundary and provides access to the geometry of the * {@code Shape} outline. If an optional {@link AffineTransform} * is specified, the coordinates returned in the iteration are * transformed accordingly. * <p> * Each call to this method returns a fresh {@code PathIterator} * object that traverses the geometry of the {@code Shape} object * independently from any other {@code PathIterator} objects in use * at the same time. * <p> * It is recommended, but not guaranteed, that objects * implementing the {@code Shape} interface isolate iterations * that are in process from any changes that might occur to the original * object's geometry during such iterations. * * @param at an optional {@code AffineTransform} to be applied to the * coordinates as they are returned in the iteration, or * {@code null} if untransformed coordinates are desired * @return a new {@code PathIterator} object, which independently * traverses the geometry of the {@code Shape}. * @since 1.2 */ public PathIterator getPathIterator(AffineTransform at); /** * Returns an iterator object that iterates along the {@code Shape} * boundary and provides access to a flattened view of the * {@code Shape} outline geometry. * <p> * Only SEG_MOVETO, SEG_LINETO, and SEG_CLOSE point types are * returned by the iterator. * <p> * If an optional {@code AffineTransform} is specified, * the coordinates returned in the iteration are transformed * accordingly. * <p> * The amount of subdivision of the curved segments is controlled * by the {@code flatness} parameter, which specifies the * maximum distance that any point on the unflattened transformed * curve can deviate from the returned flattened path segments. * Note that a limit on the accuracy of the flattened path might be * silently imposed, causing very small flattening parameters to be * treated as larger values. This limit, if there is one, is * defined by the particular implementation that is used. * <p> * Each call to this method returns a fresh {@code PathIterator} * object that traverses the {@code Shape} object geometry * independently from any other {@code PathIterator} objects in use at * the same time. * <p> * It is recommended, but not guaranteed, that objects * implementing the {@code Shape} interface isolate iterations * that are in process from any changes that might occur to the original * object's geometry during such iterations. * * @param at an optional {@code AffineTransform} to be applied to the * coordinates as they are returned in the iteration, or * {@code null} if untransformed coordinates are desired * @param flatness the maximum distance that the line segments used to * approximate the curved segments are allowed to deviate * from any point on the original curve * @return a new {@code PathIterator} that independently traverses * a flattened view of the geometry of the {@code Shape}. * @since 1.2 */ public PathIterator getPathIterator(AffineTransform at, double flatness); }