Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2005 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.swt.graphics; import org.eclipse.swt.internal.SerializableCompatibility; import org.eclipse.swt.*; /** * Instances of this class represent rectangular areas in an * (x, y) coordinate system. The top left corner of the rectangle * is specified by its x and y values, and the extent of the * rectangle is specified by its width and height. * <p> * The coordinate space for rectangles and points is considered * to have increasing values downward and to the right from its * origin making this the normal, computer graphics oriented notion * of (x, y) coordinates rather than the strict mathematical one. * </p> * <p> * The hashCode() method in this class uses the values of the public * fields to compute the hash value. When storing instances of the * class in hashed collections, do not modify these fields after the * object has been inserted. * </p> * <p> * Application code does <em>not</em> need to explicitly release the * resources managed by each instance when those instances are no longer * required, and thus no <code>dispose()</code> method is provided. * </p> * * @see Point */ public final class Rectangle implements SerializableCompatibility { /** * the x coordinate of the rectangle */ public int x; /** * the y coordinate of the rectangle */ public int y; /** * the width of the rectangle */ public int width; /** * the height of the rectangle */ public int height; static final long serialVersionUID = 3256439218279428914L; /** * Construct a new instance of this class given the * x, y, width and height values. * * @param x the x coordinate of the origin of the rectangle * @param y the y coordinate of the origin of the rectangle * @param width the width of the rectangle * @param height the height of the rectangle */ public Rectangle(int x, int y, int width, int height) { this.x = x; this.y = y; this.width = width; this.height = height; } /** * Destructively replaces the x, y, width and height values * in the receiver with ones which represent the union of the * rectangles specified by the receiver and the given rectangle. * <p> * The union of two rectangles is the smallest single rectangle * that completely covers both of the areas covered by the two * given rectangles. * </p> * * @param rect the rectangle to merge with the receiver * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> */ public void add(Rectangle rect) { if (rect == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); int left = x < rect.x ? x : rect.x; int top = y < rect.y ? y : rect.y; int lhs = x + width; int rhs = rect.x + rect.width; int right = lhs > rhs ? lhs : rhs; lhs = y + height; rhs = rect.y + rect.height; int bottom = lhs > rhs ? lhs : rhs; x = left; y = top; width = right - left; height = bottom - top; } /** * Returns <code>true</code> if the point specified by the * arguments is inside the area specified by the receiver, * and <code>false</code> otherwise. * * @param x the x coordinate of the point to test for containment * @param y the y coordinate of the point to test for containment * @return <code>true</code> if the rectangle contains the point and <code>false</code> otherwise */ public boolean contains(int x, int y) { return (x >= this.x) && (y >= this.y) && ((x - this.x) < width) && ((y - this.y) < height); } /** * Returns <code>true</code> if the given point is inside the * area specified by the receiver, and <code>false</code> * otherwise. * * @param pt the point to test for containment * @return <code>true</code> if the rectangle contains the point and <code>false</code> otherwise * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> */ public boolean contains(Point pt) { if (pt == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); return contains(pt.x, pt.y); } /** * Compares the argument to the receiver, and returns true * if they represent the <em>same</em> object using a class * specific comparison. * * @param object the object to compare with this object * @return <code>true</code> if the object is the same as this object and <code>false</code> otherwise * * @see #hashCode() */ public boolean equals(Object object) { if (object == this) return true; if (!(object instanceof Rectangle)) return false; Rectangle r = (Rectangle) object; return (r.x == this.x) && (r.y == this.y) && (r.width == this.width) && (r.height == this.height); } /** * Returns an integer hash code for the receiver. Any two * objects that return <code>true</code> when passed to * <code>equals</code> must return the same value for this * method. * * @return the receiver's hash * * @see #equals(Object) */ public int hashCode() { return x ^ y ^ width ^ height; } /** * Destructively replaces the x, y, width and height values * in the receiver with ones which represent the intersection of the * rectangles specified by the receiver and the given rectangle. * * @param rect the rectangle to intersect with the receiver * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> * * since 3.0 */ public void intersect(Rectangle rect) { if (rect == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); if (this == rect) return; int left = x > rect.x ? x : rect.x; int top = y > rect.y ? y : rect.y; int lhs = x + width; int rhs = rect.x + rect.width; int right = lhs < rhs ? lhs : rhs; lhs = y + height; rhs = rect.y + rect.height; int bottom = lhs < rhs ? lhs : rhs; x = right < left ? 0 : left; y = bottom < top ? 0 : top; width = right < left ? 0 : right - left; height = bottom < top ? 0 : bottom - top; } /** * Returns a new rectangle which represents the intersection * of the receiver and the given rectangle. * <p> * The intersection of two rectangles is the rectangle that * covers the area which is contained within both rectangles. * </p> * * @param rect the rectangle to intersect with the receiver * @return the intersection of the receiver and the argument * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> */ public Rectangle intersection(Rectangle rect) { if (rect == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); if (this == rect) return new Rectangle(x, y, width, height); int left = x > rect.x ? x : rect.x; int top = y > rect.y ? y : rect.y; int lhs = x + width; int rhs = rect.x + rect.width; int right = lhs < rhs ? lhs : rhs; lhs = y + height; rhs = rect.y + rect.height; int bottom = lhs < rhs ? lhs : rhs; return new Rectangle(right < left ? 0 : left, bottom < top ? 0 : top, right < left ? 0 : right - left, bottom < top ? 0 : bottom - top); } /** * Returns <code>true</code> if the rectangle described by the * arguments intersects with the receiver and <code>false</code> * otherwise. * <p> * Two rectangles intersect if the area of the rectangle * representing their intersection is not empty. * </p> * * @param x the x coordinate of the origin of the rectangle * @param y the y coordinate of the origin of the rectangle * @param width the width of the rectangle * @param height the height of the rectangle * @return <code>true</code> if the rectangle intersects with the receiver, and <code>false</code> otherwise * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> * * @see #intersection(Rectangle) * @see #isEmpty() * * @since 3.0 */ public boolean intersects(int x, int y, int width, int height) { return (x < this.x + this.width) && (y < this.y + this.height) && (x + width > this.x) && (y + height > this.y); } /** * Returns <code>true</code> if the given rectangle intersects * with the receiver and <code>false</code> otherwise. * <p> * Two rectangles intersect if the area of the rectangle * representing their intersection is not empty. * </p> * * @param rect the rectangle to test for intersection * @return <code>true</code> if the rectangle intersects with the receiver, and <code>false</code> otherwise * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> * * @see #intersection(Rectangle) * @see #isEmpty() */ public boolean intersects(Rectangle rect) { if (rect == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); return rect == this || intersects(rect.x, rect.y, rect.width, rect.height); } /** * Returns <code>true</code> if the receiver does not cover any * area in the (x, y) coordinate plane, and <code>false</code> if * the receiver does cover some area in the plane. * <p> * A rectangle is considered to <em>cover area</em> in the * (x, y) coordinate plane if both its width and height are * non-zero. * </p> * * @return <code>true</code> if the receiver is empty, and <code>false</code> otherwise */ public boolean isEmpty() { return (width <= 0) || (height <= 0); } /** * Returns a string containing a concise, human-readable * description of the receiver. * * @return a string representation of the rectangle */ public String toString() { return "Rectangle {" + x + ", " + y + ", " + width + ", " + height + "}"; //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ //$NON-NLS-5$ } /** * Returns a new rectangle which represents the union of * the receiver and the given rectangle. * <p> * The union of two rectangles is the smallest single rectangle * that completely covers both of the areas covered by the two * given rectangles. * </p> * * @param rect the rectangle to perform union with * @return the union of the receiver and the argument * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the argument is null</li> * </ul> * * @see #add(Rectangle) */ public Rectangle union(Rectangle rect) { if (rect == null) SWT.error(SWT.ERROR_NULL_ARGUMENT); int left = x < rect.x ? x : rect.x; int top = y < rect.y ? y : rect.y; int lhs = x + width; int rhs = rect.x + rect.width; int right = lhs > rhs ? lhs : rhs; lhs = y + height; rhs = rect.y + rect.height; int bottom = lhs > rhs ? lhs : rhs; return new Rectangle(left, top, right - left, bottom - top); } }