Java设计模式——Facade(外观)模式

本文主要是介绍Java设计模式——Facade(外观)模式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

Facade(外观)模式是一个功能介于工具包和完整应用程序之间的类，可提供包或子系统中类的简化功能。

Facade模式通常起源于普通的程序开发。当从多个不同类中分离你的代码时，可能需要通过提取访问子系统的类来重构系统。

/** Copyright (c) 2001, 2005. Steven J. Metsker.* * Steve Metsker makes no representations or warranties about* the fitness of this software for any particular purpose, * including the implied warranty of merchantability.** Please use this software as you wish with the sole* restriction that you may not claim that you wrote it.*/import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
/*** This class displays pair of functions in a panel. The functions* are x and y functions, parameterized by time. As the panel plots,* time goes 0 to 1.*/
public class PlotPanel extends JPanel {private int points;private int[] xPoints;private int[] yPoints;private Function xFunction;private Function yFunction;/*** Create a plot calculated from the provided x and y functions.* These functions must be functions of time; time goes 0 to 1* as the panel plots.*/public PlotPanel(int nPoint, Function xFunc, Function yFunc) {points = nPoint;xPoints = new int[points];yPoints = new int[points];xFunction = xFunc;yFunction = yFunc;setBackground(Color.WHITE);}protected void paintComponent(Graphics graphics) {double w = getWidth() - 1;double h = getHeight() - 1;for (int i = 0; i < points; i++) {double t = ((double) i) / (points - 1);xPoints[i] = (int) (xFunction.f(t) * w);yPoints[i] = (int) (h * (1 - yFunction.f(t)));}graphics.drawPolyline(xPoints, yPoints, points);}
}

/** Copyright (c) 2001, 2005. Steven J. Metsker.* * Steve Metsker makes no representations or warranties about* the fitness of this software for any particular purpose, * including the implied warranty of merchantability.** Please use this software as you wish with the sole* restriction that you may not claim that you wrote it.*/import java.awt.Dimension;import javax.swing.JFrame;public class ShowFlight {/** Show the flight path of a nonexploding aerial shell.*/public static void main(String[] args) {PlotPanel p = new PlotPanel(101, new T(), new ShowFlight().new YFunction());p.setPreferredSize(new Dimension(300, 200));JFrame frame = new JFrame("Flight Path for Shell Duds");frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  frame.getContentPane().add(UI.NORMAL.createTitledPanel("Flight Path", p));frame.pack();frame.setVisible(true);}private class YFunction extends Function {public YFunction() {super(new Function[] {});}public double f(double t) {// y is 0 at t = 0, 1; y is 1 at t = .5return 4 * t * (1 - t);}}
}

其他的类

public abstract class Function {protected Function[] sources;/*** Construct a function that decorates the provided source function.* * @param f*            the source function that this function wraps*/public Function(Function f) {this(new Function[] { f });}/*** Construct a function that decorates the provided source functions.* * @param sources*            the source functions that this function wraps*/public Function(Function[] sources) {this.sources = sources;}/*** The function that subclasses must implement -- see the subclases for* examples.* * @param t*            normalized time, a value between 0 and 1* @return a function value*/public abstract double f(double t);/*** @return a textual representation of this function.*/public String toString() {String name = this.getClass().toString();StringBuffer buf = new StringBuffer(name);if (sources.length > 0) {buf.append('(');for (int i = 0; i < sources.length; i++) {if (i > 0)buf.append(", ");buf.append(sources[i]);}buf.append(')');}return buf.toString();}
}

public class T extends Function {/*** Construct the identity function that returns the value of t.*/public T() {super(new Function[] {});}/*** @return the current value of t.* @param t*            time*/public double f(double t) {return t;}
}

import java.awt.*;import javax.swing.*;
import javax.swing.border.BevelBorder;
import javax.swing.border.TitledBorder;/*** User interface utilities.*/public class UI {protected Font font = new Font("Book Antiqua", Font.PLAIN, 18);public static final int STANDARD_PAD = 10;public static final UI NORMAL = new UI();/*** @return a standard font that subclasses can override*/public Font getFont() {return font;}/*** @return a standard padding amount that subclasses can override*/public int getPad() {return STANDARD_PAD;}/*** @return a standard button*/public JButton createButton() {JButton button = new JButton();button.setSize(128, 128);button.setFont(getFont());button.setVerticalTextPosition(SwingConstants.BOTTOM);button.setHorizontalTextPosition(SwingConstants.CENTER);return button;}/*** @return a standard OK! (or affirmation) button*/public JButton createButtonOk() {JButton button = createButton();button.setIcon(getIcon("images/rocket-large.gif"));button.setText("Ok!");return button;}/*** @return a standard Cancel! (or negation) button*/public JButton createButtonCancel() {JButton button = createButton();button.setIcon(getIcon("images/rocket-large-down.gif"));button.setText("Cancel!");return button;}/*** @return a panel with a standard amount of padding around any controls*/public JPanel createPaddedPanel() {JPanel panel = new JPanel();panel.setBorder(BorderFactory.createEmptyBorder(getPad(), getPad(), getPad(), getPad()));return panel;}/*** @return a panel with a standard amount of padding around any particular*         control* @param c*            the control*/public JPanel createPaddedPanel(Component c) {JPanel panel = createPaddedPanel();panel.add(c);return panel;}public static Icon getIcon(String imageName) {return new ImageIcon(imageName);}public JList createList(Object[] contents) {JList result = new JList(contents);result.setFont(getFont()); result.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);return result;}/*** @return a titled border with the given title.*/public TitledBorder createTitledBorder(String title) {TitledBorder border = BorderFactory.createTitledBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED), title,TitledBorder.LEFT, TitledBorder.TOP);border.setTitleColor(Color.black);border.setTitleFont(getFont());return border;}/*** @return a new panel that wraps a titled border around a given panel.*/public JPanel createTitledPanel(String title, JPanel in) {JPanel out = new JPanel();out.add(in);out.setBorder(createTitledBorder(title));return out;}
}