Java是世界上最流行的编程语言之一，它被广泛用于从Web开发到移动应用的各种应用程序。大部分Java工程师主要是用IDEA、Eclipse为主，这两个开发工具由于有强大的能力，所以复杂度上就更高一些。如果您刚刚开始使用Java，或者您更适合从一个轻量级的开发环境开始。所以，今天就给大家推荐一个比IDEA更好的选择：BlueJ
BlueJ简介
BlueJ是一个免费的、开源的Java开发环境，专为初学者设计。它由英国肯特大学开发，已被全球数百万学生和教育工作者使用。
下载方法
使用方法
预赛一旦你登录到系统，去开始菜单，然后bluej。单击Bluel选项。这将启动BlueJ。您将看到一个类似如下的窗口:
开始使用BlueJ在Java世界中，正在开发的程序被称为项目。一个Java程序通常由几个文件组成。您需要做的第一件事是建立您自己的项目。
任务1：在BlueJ窗口中选择“项目”->“新项目”。
您将看到一个对话框:
导航到要为项目使用的位置。这可能是一个名为xxx的文件夹。在文件名字段中输入项目的名称。你已经创建了一个文件夹，其中包含两个文件:
一个是一个文本文件，可用于记录有关项目的注释。
下一个是属于BlueJ的。它包含BlueJ使用的管理信息。检查文件夹文件是否已使用Windows资源管理器创建。
下一个阶段是创建一些文件。通常你们会这么做，但在这部分实验中我们会给你们提供一些文件。这些文件被为:
Canvas.java
Circle.java
Square.java
Triangle.java
将这些文件复制到文件夹中。代码附在文末。
选择编辑，然后选择“从文件添加类”。您将看到一个文件选择对话框。移动到文件夹并选择4个java文件。
您需要单击BlueJ工具栏中的Compile按钮。你现在应该看到类似这样的内容:
现在可以探索这个项目：
1. 右键单击Square类并选择new Square()。在出现的“Create Object”对话框中单击Ok。
2. 右键单击对象工作台中的Square对象。
你会看到一份可供你使用的方法清单。选择makeVisible()。一个小窗口将显示一个正方形在其默认位置和默认颜色。
你要开始一个新的练习使用类的形状项目，我们需要重置画布。进入菜单栏的“工具”，选择“重置Java虚拟机”。这具有重新启动项目的效果。
通过以上方法可以画出下面效果的小房子。
Canvas.java
import javax.swing.*; import java.awt.*; import java.util.List; import java.util.*; /** * Canvas is a class to allow for simple graphical drawing on a canvas. * This is a modification of the general purpose Canvas, specially made for * the BlueJ "shapes" example. * * @author: Bruce Quig * @author: Michael Kolling (mik) * * @version: 1.6 (shapes) */ public class Canvas { // Note: The implementation of this class (specifically the handling of // shape identity and colors) is slightly more complex than necessary. This // is done on purpose to keep the interface and instance fields of the // shape objects in this project clean and simple for educational purposes. private static Canvas canvasSingleton; /** * Factory method to get the canvas singleton object. */ public static Canvas getCanvas() { if(canvasSingleton == null) { canvasSingleton = new Canvas("BlueJ Shapes Demo", 300, 300, Color.white); } canvasSingleton.setVisible(true); return canvasSingleton; } // ----- instance part ----- private JFrame frame; private CanvasPane canvas; private Graphics2D graphic; private Color backgroundColour; private Image canvasImage; private List<Object> objects; private HashMap<Object, ShapeDescription> shapes; /** * Create a Canvas. * @param title title to appear in Canvas Frame * @param width the desired width for the canvas * @param height the desired height for the canvas * @param bgClour the desired background colour of the canvas */ private Canvas(String title, int width, int height, Color bgColour) { frame = new JFrame(); canvas = new CanvasPane(); frame.setContentPane(canvas); frame.setTitle(title); canvas.setPreferredSize(new Dimension(width, height)); backgroundColour = bgColour; frame.pack(); objects = new ArrayList<Object>(); shapes = new HashMap<Object, ShapeDescription> (); } /** * Set the canvas visibility and brings canvas to the front of screen * when made visible. This method can also be used to bring an already * visible canvas to the front of other windows. * @param visible boolean value representing the desired visibility of * the canvas (true or false) */ public void setVisible(boolean visible) { if(graphic == null) { // first time: instantiate the offscreen image and fill it with // the background colour Dimension size = canvas.getSize(); canvasImage = canvas.createImage(size.width, size.height); graphic = (Graphics2D)canvasImage.getGraphics(); graphic.setColor(backgroundColour); graphic.fillRect(0, 0, size.width, size.height); graphic.setColor(Color.black); } frame.setVisible(visible); } /** * Draw a given shape onto the canvas. * @param referenceObject an object to define identity for this shape * @param color the color of the shape * @param shape the shape object to be drawn on the canvas */ // Note: this is a slightly backwards way of maintaining the shape // objects. It is carefully designed to keep the visible shape interfaces // in this project clean and simple for educational purposes. public void draw(Object referenceObject, String color, Shape shape) { objects.remove(referenceObject); // just in case it was already there objects.add(referenceObject); // add at the end shapes.put(referenceObject, new ShapeDescription(shape, color)); redraw(); } /** * Erase a given shape's from the screen. * @param referenceObject the shape object to be erased */ public void erase(Object referenceObject) { objects.remove(referenceObject); // just in case it was already there shapes.remove(referenceObject); redraw(); } /** * Set the foreground colour of the Canvas. * @param newColour the new colour for the foreground of the Canvas */ public void setForegroundColor(String colorString) { if(colorString.equals("red")) graphic.setColor(Color.red); else if(colorString.equals("black")) graphic.setColor(Color.black); else if(colorString.equals("blue")) graphic.setColor(Color.blue); else if(colorString.equals("yellow")) graphic.setColor(Color.yellow); else if(colorString.equals("green")) graphic.setColor(Color.green); else if(colorString.equals("magenta")) graphic.setColor(Color.magenta); else if(colorString.equals("white")) graphic.setColor(Color.white); else graphic.setColor(Color.black); } /** * Wait for a specified number of milliseconds before finishing. * This provides an easy way to specify a small delay which can be * used when producing animations. * @param milliseconds the number */ public void wait(int milliseconds) { try { Thread.sleep(milliseconds); } catch (Exception e) { // ignoring exception at the moment } } /** * Redraw ell shapes currently on the Canvas. */ private void redraw() { erase(); for(Iterator i=objects.iterator(); i.hasNext(); ) { ((ShapeDescription)shapes.get(i.next())).draw(graphic); } canvas.repaint(); } /** * Erase the whole canvas. (Does not repaint.) */ private void erase() { Color original = graphic.getColor(); graphic.setColor(backgroundColour); Dimension size = canvas.getSize(); graphic.fill(new Rectangle(0, 0, size.width, size.height)); graphic.setColor(original); } /************************************************************************ * Inner class CanvasPane - the actual canvas component contained in the * Canvas frame. This is essentially a JPanel with added capability to * refresh the image drawn on it. */ private class CanvasPane extends JPanel { public void paint(Graphics g) { g.drawImage(canvasImage, 0, 0, null); } } /************************************************************************ * Inner class CanvasPane - the actual canvas component contained in the * Canvas frame. This is essentially a JPanel with added capability to * refresh the image drawn on it. */ private class ShapeDescription { private Shape shape; private String colorString; public ShapeDescription(Shape shape, String color) { this.shape = shape; colorString = color; } public void draw(Graphics2D graphic) { setForegroundColor(colorString); graphic.fill(shape); } } }
Circle.java
import java.awt.*; import java.awt.geom.*; /** * A circle that can be manipulated and that draws itself on a canvas. * * @author Michael Kolling and David J. Barnes * @version 1.0 (15 July 2000) */ public class Circle { private int diameter; private int xPosition; private int yPosition; private String color; private boolean isVisible; /** * Create a new circle at default position with default color. */ public Circle() { diameter = 30; xPosition = 20; yPosition = 60; color = "blue"; isVisible = false; } /** * Make this circle visible. If it was already visible, do nothing. */ public void makeVisible() { isVisible = true; draw(); } /** * Make this circle invisible. If it was already invisible, do nothing. */ public void makeInvisible() { erase(); isVisible = false; } /** * Move the circle a few pixels to the right. */ public void moveRight() { moveHorizontal(20); } /** * Move the circle a few pixels to the left. */ public void moveLeft() { moveHorizontal(-20); } /** * Move the circle a few pixels up. */ public void moveUp() { moveVertical(-20); } /** * Move the circle a few pixels down. */ public void moveDown() { moveVertical(20); } /** * Move the circle horizontally by 'distance' pixels. */ public void moveHorizontal(int distance) { erase(); xPosition += distance; draw(); } /** * Move the circle vertically by 'distance' pixels. */ public void moveVertical(int distance) { erase(); yPosition += distance; draw(); } /** * Slowly move the circle horizontally by 'distance' pixels. */ public void slowMoveHorizontal(int distance) { int delta; if(distance < 0) { delta = -1; distance = -distance; } else { delta = 1; } for(int i = 0; i < distance; i++) { xPosition += delta; draw(); } } /** * Slowly move the circle vertically by 'distance' pixels. */ public void slowMoveVertical(int distance) { int delta; if(distance < 0) { delta = -1; distance = -distance; } else { delta = 1; } for(int i = 0; i < distance; i++) { yPosition += delta; draw(); } } /** * Change the size to the new size (in pixels). Size must be >= 0. */ public void changeSize(int newDiameter) { erase(); diameter = newDiameter; draw(); } /** * Change the color. Valid colors are "red", "yellow", "blue", "green", * "magenta" and "black". */ public void changeColor(String newColor) { color = newColor; draw(); } /* * Draw the circle with current specifications on screen. */ private void draw() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.draw(this, color, new Ellipse2D.Double(xPosition, yPosition, diameter, diameter)); canvas.wait(10); } } /* * Erase the circle on screen. */ private void erase() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.erase(this); } } }
Square.java
import java.awt.*; /** * A square that can be manipulated and that draws itself on a canvas. * * @author Michael Kolling and David J. Barnes * @version 1.0 (15 July 2000) */ public class Square { private int size; private int xPosition; private int yPosition; private String color; private boolean isVisible; /** * Create a new square at default position with default color. */ public Square() { size = 30; xPosition = 60; yPosition = 50; color = "red"; isVisible = false; } /** * Make this square visible. If it was already visible, do nothing. */ public void makeVisible() { isVisible = true; draw(); } /** * Make this square invisible. If it was already invisible, do nothing. */ public void makeInvisible() { erase(); isVisible = false; } /** * Move the square a few pixels to the right. */ public void moveRight() { moveHorizontal(20); } /** * Move the square a few pixels to the left. */ public void moveLeft() { moveHorizontal(-20); } /** * Move the square a few pixels up. */ public void moveUp() { moveVertical(-20); } /** * Move the square a few pixels down. */ public void moveDown() { moveVertical(20); } /** * Move the square horizontally by 'distance' pixels. */ public void moveHorizontal(int distance) { erase(); xPosition += distance; draw(); } /** * Move the square vertically by 'distance' pixels. */ public void moveVertical(int distance) { erase(); yPosition += distance; draw(); } /** * Slowly move the square horizontally by 'distance' pixels. */ public void slowMoveHorizontal(int distance) { int delta; if(distance < 0) { delta = -1; distance = -distance; } else { delta = 1; } for(int i = 0; i < distance; i++) { xPosition += delta; draw(); } } /** * Slowly move the square vertically by 'distance' pixels. */ public void slowMoveVertical(int distance) { int delta; if(distance < 0) { delta = -1; distance = -distance; } else { delta = 1; } for(int i = 0; i < distance; i++) { yPosition += delta; draw(); } } /** * Change the size to the new size (in pixels). Size must be >= 0. */ public void changeSize(int newSize) { erase(); size = newSize; draw(); } /** * Change the color. Valid colors are "red", "yellow", "blue", "green", * "magenta" and "black". */ public void changeColor(String newColor) { color = newColor; draw(); } /* * Draw the square with current specifications on screen. */ private void draw() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.draw(this, color, new Rectangle(xPosition, yPosition, size, size)); canvas.wait(10); } } /* * Erase the square on screen. */ private void erase() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.erase(this); } } }
Triangle.java
import java.awt.*; /** * A triangle that can be manipulated and that draws itself on a canvas. * * @author Michael Kolling and David J. Barnes * @version 1.0 (15 July 2000) */ public class Triangle { private int height; private int width; private int xPosition; private int yPosition; private String color; private boolean isVisible; /** * Create a new triangle at default position with default color. */ public Triangle() { height = 30; width = 40; xPosition = 50; yPosition = 15; color = "green"; isVisible = false; } /** * Make this triangle visible. If it was already visible, do nothing. */ public void makeVisible() { isVisible = true; draw(); } /** * Make this triangle invisible. If it was already invisible, do nothing. */ public void makeInvisible() { erase(); isVisible = false; } /** * Move the triangle a few pixels to the right. */ public void moveRight() { moveHorizontal(20); } /** * Move the triangle a few pixels to the left. */ public void moveLeft() { moveHorizontal(-20); } /** * Move the triangle a few pixels up. */ public void moveUp() { moveVertical(-20); } /** * Move the triangle a few pixels down. */ public void moveDown() { moveVertical(20); } /** * Move the triangle horizontally by 'distance' pixels. */ public void moveHorizontal(int distance) { erase(); xPosition += distance; draw(); } /** * Move the triangle vertically by 'distance' pixels. */ public void moveVertical(int distance) { erase(); yPosition += distance; draw(); } /** * Slowly move the triangle horizontally by 'distance' pixels. */ public void slowMoveHorizontal(int distance) { int delta; if(distance < 0) { delta = -1; distance = -distance; } else { delta = 1; } for(int i = 0; i < distance; i++) { xPosition += delta; draw(); } } /** * Slowly move the triangle vertically by 'distance' pixels. */ public void slowMoveVertical(int distance) { int delta; if(distance < 0) { delta = -1; distance = -distance; } else { delta = 1; } for(int i = 0; i < distance; i++) { yPosition += delta; draw(); } } /** * Change the size to the new size (in pixels). Size must be >= 0. */ public void changeSize(int newHeight, int newWidth) { erase(); height = newHeight; width = newWidth; draw(); } /** * Change the color. Valid colors are "red", "yellow", "blue", "green", * "magenta" and "black". */ public void changeColor(String newColor) { color = newColor; draw(); } /* * Draw the triangle with current specifications on screen. */ private void draw() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); int[] xpoints = { xPosition, xPosition + (width/2), xPosition - (width/2) }; int[] ypoints = { yPosition, yPosition + height, yPosition + height }; canvas.draw(this, color, new Polygon(xpoints, ypoints, 3)); canvas.wait(10); } } /* * Erase the triangle on screen. */ private void erase() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.erase(this); } } }
