Java 嵌套在另一个形状中的反弹形状(此代码有什么问题)

Java 嵌套在另一个形状中的反弹形状(此代码有什么问题),java,oop,arraylist,Java,Oop,Arraylist,我有一个应用程序,它在一个JPanel中反弹形状。当形状碰到一侧时,它们会朝另一个方向反弹。我试图添加一个名为NestingShape的新形状,它包含零个或多个shape在其内部反弹,而NestingShape在JPanel中反弹。嵌套形状实例的子对象可以是简单的形状或其他嵌套形状实例 现在,我在使用NestingShape子类中的move(width,height)方法在NestingShape中移动NestingShape的子对象时遇到问题。我在Shape超类中开发一个方法时也遇到了问题,该

我有一个应用程序,它在一个JPanel中反弹
形状
。当形状碰到一侧时,它们会朝另一个方向反弹。我试图添加一个名为
NestingShape
的新形状,它包含零个或多个
shape
在其内部反弹,而
NestingShape
在JPanel中反弹。
嵌套形状
实例的子对象可以是简单的
形状
或其他
嵌套形状
实例

现在,我在使用NestingShape子类中的
move(width,height)
方法在
NestingShape
中移动
NestingShape
的子对象时遇到问题。我在
Shape
超类中开发一个方法时也遇到了问题,该方法可以在任何给定的形状中找到父对象。我将复制并粘贴我迄今为止为下面的
Shape
超类和
NestingShape
子类提出的代码,以及我目前用于测试代码的测试用例:

Shape
超类:

注意:parent()和path()方法是与此任务最相关的方法,parent()方法是我在实现时遇到问题的方法。有很多小细节,比如
fFill
count
,这些都与我开发的不同
形状相关,可以忽略

package bounce;

import java.awt.Color;
import java.util.List;

/**
 * Abstract superclass to represent the general concept of a Shape. This class
 * defines state common to all special kinds of Shape instances and implements
 * a common movement algorithm. Shape subclasses must override method paint()
 * to handle shape-specific painting.
 * 
 * @author wadfsd
 *
 */
public abstract class Shape {
    // === Constants for default values. ===
    protected static final int DEFAULT_X_POS = 0;

    protected static final int DEFAULT_Y_POS = 0;

    protected static final int DEFAULT_DELTA_X = 5;

    protected static final int DEFAULT_DELTA_Y = 5;

    protected static final int DEFAULT_HEIGHT = 35;

    protected static final int DEFAULT_WIDTH = 25;

    protected static final Color DEFAULT_COLOR = Color.black;

    protected static final String DEFAULT_STRING = "";
    // ===

    // === Instance variables, accessible by subclasses.
    protected int fX;

    protected int fY;

    protected int fDeltaX;

    protected int fDeltaY;

    protected int fWidth;

    protected int fHeight;

    protected boolean fFill;

    protected Color fColor;

    protected int count;

    protected int fState;

    protected int before;

    protected String fString;
    // ===

    /**
     * Creates a Shape object with default values for instance variables.
     */
    public Shape() {
        this(DEFAULT_X_POS, DEFAULT_Y_POS, DEFAULT_DELTA_X, DEFAULT_DELTA_Y, DEFAULT_WIDTH, DEFAULT_HEIGHT, DEFAULT_COLOR, DEFAULT_STRING);
    }

    /**
     * Creates a Shape object with a specified x and y position.
     */
    public Shape(int x, int y) {
        this(x, y, DEFAULT_DELTA_X, DEFAULT_DELTA_Y, DEFAULT_WIDTH, DEFAULT_HEIGHT, DEFAULT_COLOR, DEFAULT_STRING);
    }

    public Shape(int x, int y, String str) {
        this(x, y, DEFAULT_DELTA_X, DEFAULT_DELTA_Y, DEFAULT_WIDTH, DEFAULT_HEIGHT, DEFAULT_COLOR, str);
    }

    /**
     * Creates a Shape object with specified x, y, and color values.
     */
    public Shape(int x, int y, Color c) {
        this(x, y, DEFAULT_DELTA_X, DEFAULT_DELTA_Y, DEFAULT_WIDTH, DEFAULT_HEIGHT, c, DEFAULT_STRING);
    }

    public Shape(int x, int y, Color c, String str) {
        this(x, y, DEFAULT_DELTA_X, DEFAULT_DELTA_Y, DEFAULT_WIDTH, DEFAULT_HEIGHT, c, str);
    }

    /**
     * Creates a Shape instance with specified x, y, deltaX and deltaY values.
     * The Shape object is created with a default width, height and color.
     */
    public Shape(int x, int y, int deltaX, int deltaY) {
        this(x, y, deltaX, deltaY, DEFAULT_WIDTH, DEFAULT_HEIGHT, DEFAULT_COLOR, DEFAULT_STRING);
    }

    public Shape(int x, int y, int deltaX, int deltaY, String str) {
        this(x, y, deltaX, deltaY, DEFAULT_WIDTH, DEFAULT_HEIGHT, DEFAULT_COLOR, str);
    }

    /**
     * Creates a Shape instance with specified x, y, deltaX, deltaY and color values.
     * The Shape object is created with a default width and height.
     */
    public Shape(int x, int y, int deltaX, int deltaY, Color c) {
        this(x, y, deltaX, deltaY, DEFAULT_WIDTH, DEFAULT_HEIGHT, c, DEFAULT_STRING);
    }

    public Shape(int x, int y, int deltaX, int deltaY, Color c, String str) {
        this(x, y, deltaX, deltaY, DEFAULT_WIDTH, DEFAULT_HEIGHT, c, str);
    }

    /**
     * Creates a Shape instance with specified x, y, deltaX, deltaY, width and
     * height values. The Shape object is created with a default color.
     */
    public Shape(int x, int y, int deltaX, int deltaY, int width, int height) {
        this(x, y, deltaX, deltaY, width, height, DEFAULT_COLOR, DEFAULT_STRING);
    }

    public Shape(int x, int y, int deltaX, int deltaY, int width, int height, String str) {
        this(x, y, deltaX, deltaY, width, height, DEFAULT_COLOR, str);
    }

    public Shape(int x, int y, int deltaX, int deltaY, int width, int height, Color c) {
        this(x, y, deltaX, deltaY, width, height, c, DEFAULT_STRING);
    }

    /**
     * Creates a Shape instance with specified x, y, deltaX, deltaY, width,
     * height and color values.
     */
    public Shape(int x, int y, int deltaX, int deltaY, int width, int height, Color c, String str) {
        fX = x;
        fY = y;
        fDeltaX = deltaX;
        fDeltaY = deltaY;
        fWidth = width;
        fHeight = height;
        fFill = false;
        fColor = c;
        count = 0;
        fState = 1;
        before = 0;
        fString = str;
    }

    /**
     * Moves this Shape object within the specified bounds. On hitting a 
     * boundary the Shape instance bounces off and back into the two- 
     * dimensional world and logs whether a vertical or horizontal wall
     * was hit for the DynamicRectangleShape.
     * @param width width of two-dimensional world.
     * @param height height of two-dimensional world.
     */
    public void move(int width, int height) {
        int nextX = fX + fDeltaX;
        int nextY = fY + fDeltaY;

        if (nextY <= 0) {
            nextY = 0;
            fDeltaY = -fDeltaY;
            fFill = false;
            count++;
        } else if (nextY + fHeight >= height) {
            nextY = height - fHeight;
            fDeltaY = -fDeltaY;
            fFill = false;
            count++;
        }

        // When Shape hits a corner the vertical wall fFill value overrides the horizontal
        if (nextX <= 0) {
            nextX = 0;
            fDeltaX = -fDeltaX;
            fFill = true;
            count++;
        } else if (nextX + fWidth >= width) {
            nextX = width - fWidth;
            fDeltaX = -fDeltaX;
            fFill = true;
            count++;
        }

        fX = nextX;
        fY = nextY;
    }

    public void text(Painter painter, String str) {
        painter.drawCentredText(str, fX, fY, fWidth, fHeight);
    }

    /**
     * Returns the NestingShape that contains the Shape that method parent
     * is called on. If the callee object is not a child within a
     * NestingShape instance this method returns null.
     */
    public NestingShape parent() {
        // Related to NestingShape
    }

    /**
     * Returns an ordered list of Shape objects. The first item within the
     * list is the root NestingShape of the containment hierarchy. The last
     * item within the list is the callee object (hence this method always
     * returns a list with at least one item). Any intermediate items are
     * NestingShapes that connect the root NestingShape to the callee Shape.
     * E.g. given:
     * 
     *   NestingShape root = new NestingShape();
     *   NestingShape intermediate = new NestingShape();
     *   Shape oval = new OvalShape();
     *   root.add(intermediate);
     *   intermediate.add(oval);
     *   
     * a call to oval.path() yields: [root,intermediate,oval] 
     */
    public List<Shape> path() {
        // Related to NestingShape
    }

    /**
     * Method to be implemented by concrete subclasses to handle subclass
     * specific painting.
     * @param painter the Painter object used for drawing.
     */
    public abstract void paint(Painter painter);

    /**
     * Returns this Shape object's x position.
     */
    public int x() {
        return fX;
    }

    /**
     * Returns this Shape object's y position.
     */
    public int y() {
        return fY;
    }

    /**
     * Returns this Shape object's speed and direction.
     */
    public int deltaX() {
        return fDeltaX;
    }

    /**
     * Returns this Shape object's speed and direction.
     */
    public int deltaY() {
        return fDeltaY;
    }

    /**
     * Returns this Shape's width.
     */
    public int width() {
        return fWidth;
    }

    /**
     * Returns this Shape's height.
     */
    public int height() {
        return fHeight;
    }

    /**
     * Returns a String whose value is the fully qualified name of this class 
     * of object. E.g., when called on a RectangleShape instance, this method 
     * will return "bounce.RectangleShape".
     */
    public String toString() {
        return getClass().getName();
    }
}
TestNestingShape
测试用例:

package bounce;

import java.util.List;

import junit.framework.TestCase;

/**
 * Class to test class NestingShape according to its specification.
 */
public class TestNestingShape extends TestCase {

    private NestingShape topLevelNest;
    private NestingShape midLevelNest;
    private NestingShape bottomLevelNest;
    private Shape simpleShape;

    public TestNestingShape(String name) {
        super(name);
    }

    /**
     * Creates a Shape composition hierarchy with the following structure:
     *   NestingShape (topLevelNest)
     *     |
     *     --- NestingShape (midLevelNest)
     *           |
     *           --- NestingShape (bottomLevelNest)
     *           |
     *           --- RectangleShape (simpleShape)
     */
    protected void setUp() throws Exception {
        topLevelNest = new NestingShape(0, 0, 2, 2, 100, 100);
        midLevelNest = new NestingShape(0, 0, 2, 2, 50, 50);
        bottomLevelNest = new NestingShape(5, 5, 2, 2, 10, 10);
        simpleShape = new RectangleShape(1, 1, 1, 1, 5, 5);

        midLevelNest.add(bottomLevelNest);
        midLevelNest.add(simpleShape);
        topLevelNest.add(midLevelNest);
    }

    /**
     * Checks that methods move() and paint() correctly move and paint a 
     * NestingShape's contents.
     */
    public void testBasicMovementAndPainting() {
        Painter painter = new MockPainter();

        topLevelNest.move(500, 500);
        topLevelNest.paint(painter);
        assertEquals("(rectangle 2,2,100,100)(rectangle 2,2,50,50)(rectangle 7,7,10,10)(rectangle 2,2,5,5)", painter.toString());
    }

    /**
     * Checks that method add successfuly adds a valid Shape, supplied as 
     * argument, to a NestingShape instance. 
     */
    public void testAdd() {
        // Check that topLevelNest and midLevelNest mutually reference each other.
        assertSame(topLevelNest, midLevelNest.parent());
        assertTrue(topLevelNest.contains(midLevelNest));

        // Check that midLevelNest and bottomLevelNest mutually reference each other.
        assertSame(midLevelNest, bottomLevelNest.parent());
        assertTrue(midLevelNest.contains(bottomLevelNest));
    }

    /**
     * Check that method add throws an IlegalArgumentException when an attempt 
     * is made to add a Shape to a NestingShape instance where the Shape 
     * argument is already part of some NestingShape instance.
     */
    public void testAddWithArgumentThatIsAChildOfSomeOtherNestingShape() {
        try {
            topLevelNest.add(bottomLevelNest);
            fail();
        } catch(IllegalArgumentException e) {
            // Expected action. Ensure the state of topLevelNest and 
            // bottomLevelNest has not been changed.
            assertFalse(topLevelNest.contains(bottomLevelNest));
            assertSame(midLevelNest, bottomLevelNest.parent());
        }
    }

    /**
     * Check that method add throws an IllegalArgumentException when an attempt
     * is made to add a shape that will not fit within the bounds of the 
     * proposed NestingShape object.
     */
    public void testAddWithOutOfBoundsArgument() {
        Shape rectangle = new RectangleShape(80, 80, 2, 2, 50, 50);

        try {
            topLevelNest.add(rectangle);
            fail();
        } catch(IllegalArgumentException e) {
            // Expected action. Ensure the state of topLevelNest and 
            // rectangle has not been changed.
            assertFalse(topLevelNest.contains(rectangle));
            assertNull(rectangle.parent());
        }
    }

    /**
     * Check that method remove breaks the two-way link between the Shape 
     * object that has been removed and the NestingShape it was once part of.
     */
    public void testRemove() {
        topLevelNest.remove(midLevelNest);
        assertFalse(topLevelNest.contains(midLevelNest));
        assertNull(midLevelNest.parent());
    }

    /**
     * Check that method shapeAt returns the Shape object that is held at a
     * specified position within a NestingShape instance.
     */
    public void testShapeAt() {
        assertSame(midLevelNest, topLevelNest.shapeAt(0));
    }

    /**
     * Check that method shapeAt throws a IndexOutOfBoundsException when called
     * with an invalid index argument.
     */
    public void testShapeAtWithInvalidIndex() {
        try {
            topLevelNest.shapeAt(1);
            fail();
        } catch(IndexOutOfBoundsException e) {
            // Expected action.
        }
    }

    /**
     * Check that method shapeCount returns zero when called on a NestingShape
     * object without children.
     */
    public void testShapeCountOnEmptyParent() {
        assertEquals(0, bottomLevelNest.shapeCount());
    }

    /**
     * Check that method shapeCount returns the number of children held within 
     * a NestingShape instance - where the number of children > 0.
     */
    public void testShapeCountOnNonEmptyParent() {
        assertEquals(2, midLevelNest.shapeCount());
    }

    /**
     * Check that method indexOf returns the index position within a
     * NestingShape instance of a Shape held within the NestingShape. 
     */
    public void testIndexOfWith() {
        assertEquals(0, topLevelNest.indexOf(midLevelNest));
        assertEquals(1, midLevelNest.indexOf(simpleShape));
    }

    /**
     * Check that method indexOf returns -1 when called with an argument that
     * is not part of the NestingShape callee object.
     */
    public void testIndexOfWithNonExistingChild() {
        assertEquals(-1, topLevelNest.indexOf(bottomLevelNest));
    }

    /**
     * Check that Shape's path method correctly returns the path from the root
     * NestingShape object through to the Shape object that path is called on.
     */
    public void testPath() {
        List<Shape> path = simpleShape.path();

        assertEquals(3, path.size());
        assertSame(topLevelNest, path.get(0));
        assertSame(midLevelNest, path.get(1));
        assertSame(simpleShape, path.get(2));
    }

    /**
     * Check that Shape's path method correctly returns a singleton list
     * containing only the callee object when this Shape object has no parent.
     */
    public void testPathOnShapeWithoutParent() {
        List<Shape> path = topLevelNest.path();

        assertEquals(1, path.size());
        assertSame(topLevelNest, path.get(0));
    }
}
包反弹;
导入java.util.List;
导入junit.framework.TestCase;
/**
*类根据其规范测试类嵌套形状。
*/
公共类TestNestingShape扩展了TestCase{
私人巢穴形状顶层巢穴;
私有巢形中层巢;
私人筑巢形状底部水平巢;
私人形状的简单造型;
公共测试嵌套形状(字符串名称){
超级(姓名);
}
/**
*创建具有以下结构的形状组合层次结构:
*嵌套形状(顶层嵌套)
*     |
*---嵌套形状(中层嵌套)
*           |
*---嵌套形状(底部水平嵌套)
*           |
*---矩形形状(简单形状)
*/
受保护的void setUp()引发异常{
topLevelNest=新的嵌套形状(0,0,2,2100,100);
中层嵌套=新嵌套形状(0,0,2,2,50,50);
bottomLevelNest=新的嵌套形状(5,5,2,2,10,10);
simpleShape=新矩形形状(1,1,1,1,5,5);
middlevelnest.add(bottomLevelNest);
添加(simpleShape);
添加(中间层嵌套);
}
/**
*检查方法move()和paint()是否正确地移动和绘制
*嵌套形状的内容。
*/
公共无效测试基本移动和绘制(){
Painter Painter=新的MockPainter();
顶层嵌套移动(500500);
面漆(油漆工);
assertEquals(“(矩形2,21001000)(矩形2,2,50,50)(矩形7,7,10,10)(矩形2,2,5,5)”,painter.toString();
}
/**
*检查方法add是否成功添加了有效的形状,如所示
*参数设置为嵌套形状实例。
*/
公共无效测试dd(){
//检查topLevelNest和MiddlevelNest是否相互引用。
assertSame(topLevelNest、midLevelNest.parent());
assertTrue(topLevelNest.contains(midLevelNest));
//检查midLevelNest和bottomLevelNest是否相互引用。
assertSame(midLevelNest、bottomLevelNest.parent());
assertTrue(midLevelNest.contains(bottomLevelNest));
}
/**
*检查add方法在尝试时是否引发IlegalArgumentException
*用于将形状添加到嵌套形状实例中,其中
*参数已经是某些NestingShape实例的一部分。
*/
公共无效,以属于其他嵌套形状()之子的论点进行测试{
试一试{
topLevelNest.add(bottomLevelNest);
失败();
}捕获(IllegalArgumentException e){
//预期操作。确保topLevelNest和
//bottomLevelNest尚未更改。
assertFalse(topLevelNest.contains(bottomLevelNest));
assertSame(midLevelNest、bottomLevelNest.parent());
}
}
/**
*检查add方法在尝试时是否引发IllegalArgumentException
*用于添加一个不适合对象边界的形状
*建议的嵌套形状对象。
*/
无边界的公共无效测试(){
形状矩形=新矩形形状(80,80,2,2,50,50);
试一试{
添加(矩形);
失败();
}捕获(IllegalArgumentException e){
//预期操作。确保topLevelNest和
//矩形尚未更改。
assertFalse(topLevelNest.contains(矩形));
assertNull(rectangle.parent());
}
}
/**
*检查“移除”方法是否会断开形状之间的双向链接
*已移除的对象及其曾经是其一部分的嵌套形状。
*/
公共void testRemove(){
顶层嵌套。移除(中层嵌套);
assertFalse(topLevelNest.contains(midLevelNest));
assertNull(midLevelNest.parent());
}
/**
*检查shapeAt方法是否返回保存在
*NestingShape实例中的指定位置。
*/
公共void testShapeAt(){
assertSame(MiddlevelNest、topLevelNest.shapeAt(0));
}
/**
*检查方法shapeAt在调用时是否抛出IndexOutOfBoundsException
*具有无效的索引参数。
*/
public void testShapeAtWithInvalidIndex(){
试一试{
顶部水平槽形槽(1);
失败();
}catch(IndexOutOfBoundsException e){
package bounce;

import java.util.List;

import junit.framework.TestCase;

/**
 * Class to test class NestingShape according to its specification.
 */
public class TestNestingShape extends TestCase {

    private NestingShape topLevelNest;
    private NestingShape midLevelNest;
    private NestingShape bottomLevelNest;
    private Shape simpleShape;

    public TestNestingShape(String name) {
        super(name);
    }

    /**
     * Creates a Shape composition hierarchy with the following structure:
     *   NestingShape (topLevelNest)
     *     |
     *     --- NestingShape (midLevelNest)
     *           |
     *           --- NestingShape (bottomLevelNest)
     *           |
     *           --- RectangleShape (simpleShape)
     */
    protected void setUp() throws Exception {
        topLevelNest = new NestingShape(0, 0, 2, 2, 100, 100);
        midLevelNest = new NestingShape(0, 0, 2, 2, 50, 50);
        bottomLevelNest = new NestingShape(5, 5, 2, 2, 10, 10);
        simpleShape = new RectangleShape(1, 1, 1, 1, 5, 5);

        midLevelNest.add(bottomLevelNest);
        midLevelNest.add(simpleShape);
        topLevelNest.add(midLevelNest);
    }

    /**
     * Checks that methods move() and paint() correctly move and paint a 
     * NestingShape's contents.
     */
    public void testBasicMovementAndPainting() {
        Painter painter = new MockPainter();

        topLevelNest.move(500, 500);
        topLevelNest.paint(painter);
        assertEquals("(rectangle 2,2,100,100)(rectangle 2,2,50,50)(rectangle 7,7,10,10)(rectangle 2,2,5,5)", painter.toString());
    }

    /**
     * Checks that method add successfuly adds a valid Shape, supplied as 
     * argument, to a NestingShape instance. 
     */
    public void testAdd() {
        // Check that topLevelNest and midLevelNest mutually reference each other.
        assertSame(topLevelNest, midLevelNest.parent());
        assertTrue(topLevelNest.contains(midLevelNest));

        // Check that midLevelNest and bottomLevelNest mutually reference each other.
        assertSame(midLevelNest, bottomLevelNest.parent());
        assertTrue(midLevelNest.contains(bottomLevelNest));
    }

    /**
     * Check that method add throws an IlegalArgumentException when an attempt 
     * is made to add a Shape to a NestingShape instance where the Shape 
     * argument is already part of some NestingShape instance.
     */
    public void testAddWithArgumentThatIsAChildOfSomeOtherNestingShape() {
        try {
            topLevelNest.add(bottomLevelNest);
            fail();
        } catch(IllegalArgumentException e) {
            // Expected action. Ensure the state of topLevelNest and 
            // bottomLevelNest has not been changed.
            assertFalse(topLevelNest.contains(bottomLevelNest));
            assertSame(midLevelNest, bottomLevelNest.parent());
        }
    }

    /**
     * Check that method add throws an IllegalArgumentException when an attempt
     * is made to add a shape that will not fit within the bounds of the 
     * proposed NestingShape object.
     */
    public void testAddWithOutOfBoundsArgument() {
        Shape rectangle = new RectangleShape(80, 80, 2, 2, 50, 50);

        try {
            topLevelNest.add(rectangle);
            fail();
        } catch(IllegalArgumentException e) {
            // Expected action. Ensure the state of topLevelNest and 
            // rectangle has not been changed.
            assertFalse(topLevelNest.contains(rectangle));
            assertNull(rectangle.parent());
        }
    }

    /**
     * Check that method remove breaks the two-way link between the Shape 
     * object that has been removed and the NestingShape it was once part of.
     */
    public void testRemove() {
        topLevelNest.remove(midLevelNest);
        assertFalse(topLevelNest.contains(midLevelNest));
        assertNull(midLevelNest.parent());
    }

    /**
     * Check that method shapeAt returns the Shape object that is held at a
     * specified position within a NestingShape instance.
     */
    public void testShapeAt() {
        assertSame(midLevelNest, topLevelNest.shapeAt(0));
    }

    /**
     * Check that method shapeAt throws a IndexOutOfBoundsException when called
     * with an invalid index argument.
     */
    public void testShapeAtWithInvalidIndex() {
        try {
            topLevelNest.shapeAt(1);
            fail();
        } catch(IndexOutOfBoundsException e) {
            // Expected action.
        }
    }

    /**
     * Check that method shapeCount returns zero when called on a NestingShape
     * object without children.
     */
    public void testShapeCountOnEmptyParent() {
        assertEquals(0, bottomLevelNest.shapeCount());
    }

    /**
     * Check that method shapeCount returns the number of children held within 
     * a NestingShape instance - where the number of children > 0.
     */
    public void testShapeCountOnNonEmptyParent() {
        assertEquals(2, midLevelNest.shapeCount());
    }

    /**
     * Check that method indexOf returns the index position within a
     * NestingShape instance of a Shape held within the NestingShape. 
     */
    public void testIndexOfWith() {
        assertEquals(0, topLevelNest.indexOf(midLevelNest));
        assertEquals(1, midLevelNest.indexOf(simpleShape));
    }

    /**
     * Check that method indexOf returns -1 when called with an argument that
     * is not part of the NestingShape callee object.
     */
    public void testIndexOfWithNonExistingChild() {
        assertEquals(-1, topLevelNest.indexOf(bottomLevelNest));
    }

    /**
     * Check that Shape's path method correctly returns the path from the root
     * NestingShape object through to the Shape object that path is called on.
     */
    public void testPath() {
        List<Shape> path = simpleShape.path();

        assertEquals(3, path.size());
        assertSame(topLevelNest, path.get(0));
        assertSame(midLevelNest, path.get(1));
        assertSame(simpleShape, path.get(2));
    }

    /**
     * Check that Shape's path method correctly returns a singleton list
     * containing only the callee object when this Shape object has no parent.
     */
    public void testPathOnShapeWithoutParent() {
        List<Shape> path = topLevelNest.path();

        assertEquals(1, path.size());
        assertSame(topLevelNest, path.get(0));
    }
}
private Shape parent = null;
public Shape(Shape parent) {
  this.parent = parent;
}

public void setParent(Shape parent) {
  this.parent = parent;
}

public Shape parent() {
  return parent;
}
public interface ShapeContainer {
  public List<Shape> getChildren();
  // .. more?
}
public class NestingShape extends Shape implements ShapeContainer