用Java实现一个向量场

在学习微分方程的时候，以前也写过类似的文章，可是效果不行，前几天写了一个，感觉不错，分享之。

先看效果（x*x -y -2）：

再来代码：

[java]
package com.math.slopfields;

import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;

public class SlopFields extends JFrame {
    protected static final int WIDTH = 800;
    protected static final int HEIGHT = 600;
    private java.awt.Dimension dimension = java.awt.Toolkit.getDefaultToolkit().
            getScreenSize();


    public SlopFields(String title, Grid g) {
        super(title);
        this.setSize(WIDTH, HEIGHT);
        this.setLocation((dimension.width - WIDTH) / 2,
                         (dimension.height - HEIGHT) / 2);

        HeartCanvas panel = new HeartCanvas(g);
        this.add(panel);
    }

    public static void main(String[] args) {
        double scale = 80;
        double aa = 3;
        double dd = 0.15;

        Area area = new Area(Vector.build(-aa, aa), Vector.build(aa, -aa));
        Vector grid = Vector.build(dd, dd);
        CanCalc c = new CanCalc(){
            public double doCalc(Vector v) {
                return v.x*v.x - v.y - 2;
            }

        };
        Grid g = new Grid(area, grid, c, scale);

        SlopFields hart = new SlopFields("向量场", g);
        hart.setVisible(true);
        hart.setDefaultCloseOperation(hart.EXIT_ON_CLOSE);
    }

}

class HeartCanvas extends javax.swing.JPanel {

    private Grid grid;

    public HeartCanvas(Grid g) {
        this.grid = g;
        this.grid.calcGrids();
        this.grid.preDraw();
    }

    public void paintComponent(Graphics g) {
        setBackground(Color.BLACK);
        super.paintComponent(g);
        g.setColor(Color.GREEN);
        this.grid.draw(g);
    }
}

class Grid {
    public double scale = 100;
    public double padding = 0.2;
    public Vector offect = Vector.build(0.25, 0.25);

    public Area area;
    public Area[][] areas;

    public Vector grid;
    public int nx, ny;

    private CanCalc calc;

    public Grid(Area _area, Vector _grid, CanCalc _calc, double _scale) {
        this.area = _area;
        this.grid = _grid;
        this.calc = _calc;
        this.scale = _scale;
    }

    public void draw(Graphics g) {

        int x = (int)area.ld.x;
        int y = (int)area.ld.y;
        Vector t = area.ru.add(area.ld.neg());
        int width = (int)t.x;
        int height = (int)t.y;


        g.drawRect(x, y, width, height);
        g.drawLine(x, (int)offect.y, x+width, (int)offect.y);
        g.drawLine((int)offect.x, y, (int)offect.x, y+height);
        for(Area[] al : areas) {
            for(Area a : al) {
                g.drawLine((int)a.ld.x, (int)a.ld.y, (int)a.ru.x, (int)a.ru.y);
            }
        }
    }

    public void preDraw() {
        offect = offect.dotMul(this.scale).add(Vector.build(-area.ld.x*scale, area.ru.y*scale));
        area = new Area(Vector.build(area.ld.x, -area.ru.y).dotMul(this.scale).add(offect),
                Vector.build(area.ru.x, -area.ld.x).dotMul(this.scale).add(offect));
        for(int i=0; i<ny; i++){
            for(int j=0; j<nx; j++) {
                Area tmp = areas[i][j];
                Vector va = Vector.build(tmp.ld.x, -tmp.ld.y).dotMul(this.scale).add(offect);

补充：软件开发 , Java ,