Checks if two lines are parallel - Android java.lang

Android examples for java.lang:Math Geometry

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Description

Checks if two lines are parallel

Demo Code

/*******************************************************************************
 * Copyright (c) 2011 MadRobot./*www  . j  a  va  2 s. c  om*/
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * 
 * Contributors:
 *  Elton Kent - initial API and implementation
 ******************************************************************************/
//package com.java2s;

import android.graphics.PointF;

public class Main {
    /**
     * Defines the distance below which two points are considered to coincide.
     */
    public static final double VERY_SMALL_DISTANCE = 0.000001;

    /**
     * Checks if two lines are parallel
     * 
     * @param line1
     *            he first line
     * @param line2
     *            the second line
     * @return returns true if the lines are parallel, false otherwise
     */
    public static boolean areParallel(PointF line1Start, PointF line1End,
            PointF line2Start, PointF line2End) {
        // If both lines are vertical, they are parallel
        if (isVertical(line1Start, line1End)
                && isVertical(line2Start, line2End)) {
            return true;
        } else // If one of them is vertical, they are not parallel
        if (isVertical(line1Start, line1End)
                || isVertical(line2Start, line2End)) {
            return false;
        } else // General case. If their slopes are the same, they are parallel
        {
            return (Math.abs(getSlope(line1Start, line1End)
                    - getSlope(line2Start, line2End)) < VERY_SMALL_DISTANCE);
        }
    }

    /**
     * Checks if a line is vertical.
     * 
     * @param line
     *            the line to check
     * @return returns true if the line is vertical, false otherwise.
     */
    public static boolean isVertical(PointF lineStart, PointF lineEnd) {
        return ((Math.abs(lineStart.x - lineEnd.x) < VERY_SMALL_DISTANCE));
    }

    /**
     * Return the slope of a line
     * 
     * @param lineStart
     * @param lineEnd
     * @return
     */
    public static double getSlope(PointF lineStart, PointF lineEnd) {
        return (((lineStart.y) - lineEnd.y) / ((lineStart.x) - lineEnd.x));
    }
}

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