/*
 * NewHeat1D.java
 * 2005/12/26
 *
 * コンパイル: javac NewHeat1D.java
 * 実行:       java NewHeat1D
 *
 * ダブルバッファリングを利用。一度しか計算しない。
 * 
 */

import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;


public class NewHeat1D extends Frame {
    Image im = null;
    Graphics g2 = null;
    int i, n, nMax;
    int N = 40;
    double lambda = 0.5;
    double Tmax = 10.0;
    double dt = 0.01;
    double h, tau;
    int skip;
    double [] u, newu;
    double ratiox, ratioy, X0, Y0;
    public NewHeat1D() {
        this.setSize(500, 500);
        this.addWindowListener(new WindowAdapter() {
                public void windowClosing(WindowEvent ev) {
                    System.exit(0);
                }
            });
        this.setVisible(true);
    }
    public static void main(String[] args) {
        // TODO 自動生成されたメソッド・スタブ
        new NewHeat1D();
    }
    private void space(double x0, double y0, double x1, double y1) {
        X0 = x0; Y0 = y0;
        ratiox = 500 / (x1 - x0);
        ratioy = 500 / (y1 - y0);
    }
    private int wx(double x) {
        return (int)(ratiox * (x - X0));
    }
    private int wy(double y) {
        return 500 - (int)(ratioy * (y - Y0));
    }
    private double f(double x) {
        if (x <= 0.5)
            return x;
        else
            return 1.0 - x;
    }
    public void paint(Graphics g) {
        if (im == null) {
            im = this.createImage(this.getWidth(), this.getHeight());
            g2 = im.getGraphics();
            space(-0.1, -0.1, 1.1, 1.1);
            h = 1.0 / N;
            tau = lambda * h * h;
            skip = (int)Math.rint(dt / tau);
            nMax = (int)Math.rint(Tmax / tau);
            u = new double [N+1];
            newu = new double [N+1];
            // 初期値
            for (i = 0; i <= N; i++)
                u[i] = f(i * h);
            // 初期値のグラフを描く
            for (i = 0; i < N; i++)
                g2.drawLine(wx(i * h), wy(u[i]), wx((i + 1) * h), wy(u[i+1]));
            // 時間発展
            for (n = 1; n <= nMax; n++) {
                // 陽的差分法
                for (i = 1; i < N; i++)
                    newu[i] = (1 - 2 * lambda) * u[i] + lambda * (u[i + 1] + u[i - 1]);
                for (i = 1; i < N; i++)
                    u[i] = newu[i];
                // 同次Dirichlet境界条件
                u[0] = 0.0;
                u[N] = 0.0;
                // 時刻が dt の整数倍のときにグラフを描く
                if (n % skip == 0) {
                    for (i = 0; i < N; i++)
                        g2.drawLine(wx(i * h), wy(u[i]), wx((i + 1) * h), wy(u[i+1]));
                }
                System.out.println(""+ n * tau);
            }
        }
        g.drawImage(im, 0, 0, this);
    }
}