我有一个方法，我试图修改地图的一个键的值。
我无法更改地图的签名。
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
class Sistema{
double g=10;//9.81;
double m1 = 1;
double th1 = Math.PI/2;
double w1=0;
double L1=1;
double dt=0.001;
final int N = 2;
double energiaIniziale, yPotenziale0;
ArrayList<Point2D.Double> tracciato = new ArrayList<Point2D.Double>();
public Sistema(){
double y0 = getY();
yPotenziale0 = m1*L1;
energiaIniziale = energiaCinetica()+energiaPotenziale();
System.out.println("y0:"+y0);
System.out.println("y:"+yPotenziale0 + " Tot."+energiaIniziale+" = C:"+energiaCinetica()+" P:"+energiaPotenziale());
}
synchronized ArrayList<Point2D.Double> getTracciato(){
return tracciato;
}
synchronized double energiaCinetica(){
return m1*L1*L1*w1*w1/2;
}
synchronized double energiaPotenziale(){
return m1*g*yPotenziale0+g*m1*getY();
}
synchronized double getX(){
double x1 = L1*Math.sin(th1);
return x1;
}
synchronized double getY(){
double y1 = -L1*Math.cos(th1);
return y1;
}
void simulate(){
synchronized(this){
double yin[] = new double[N];
yin[0] = th1;
yin[1] = w1;
double yout[] = runge_kutta(0, yin, dt);
this.th1 = yout[0];
this.w1 = yout[1];
//System.out.println(""+Math.toDegrees(th1)+" "+w1);
tracciato.add(new Point2D.Double(getX(), getY()));
}
}
double[] derivs(double xin, double yin[])
{
/*
yin[0] = th1[i];
yin[1] = w1[i];
yin[2] = th2[i];
yin[3] = w2[i];
*/
double dydx[] = new double[N];
/* function to fill array of derivatives dydx at xin */
dydx[0] = yin[1];
dydx[1] = -g/L1*Math.sin(th1);
return dydx;
}
double[] runge_kutta(double xin, double yin[], double h)
{
double yout[] = new double[N];
/* fourth order Runge-Kutta - see e.g. Numerical Recipes */
int i;
double hh, xh;
double dydx[] = new double[N];
double dydxt[] = new double[N];
double yt[] = new double[N];
double k1[] = new double[N];
double k2[] = new double[N];
double k3[] = new double[N];
double k4[] = new double[N];
hh = 0.5*h;
xh = xin + hh;
dydx = derivs(xin, yin); /* first step */
// System.out.print("a:");
for (i = 0; i < N; i++)
{
k1[i] = h*dydx[i];
yt[i] = yin[i] + 0.5*k1[i];
// System.out.printf(" %5.2f ",k1[i]);
}
dydxt = derivs(xh, yt); /* second step */
// System.out.print("\nb:");
for (i = 0; i < N; i++)
{
k2[i] = h*dydxt[i];
yt[i] = yin[i] + 0.5*k2[i];
// System.out.printf(" %5.2f ",k2[i]);
}
dydxt = derivs(xh, yt); /* third step */
// System.out.print("\nc:");
for (i = 0; i < N; i++)
{
k3[i] = h*dydxt[i];
yt[i] = yin[i] + k3[i];
// System.out.printf(" %5.2f ",k3[i]);
}
dydxt = derivs(xin + h, yt); /* fourth step */
// System.out.print("\nd:");
for (i = 0; i < N; i++)
{
k4[i] = h*dydxt[i];
yout[i] = yin[i] + k1[i]/6. + k2[i]/3. + k3[i]/3. + k4[i]/6.;
// System.out.printf(" %5.2f ",k4[i]);
}
// System.out.println();
return yout;
}
}
class Pannello extends JPanel implements Runnable, MouseMotionListener{
double x[];
double y[];
int offX, offY;
double scale;
final int DIM_BARRA_EN = 400;
Sistema sistema;
public Pannello(Sistema sistema){
this.sistema=sistema;
x = new double[2];
y = new double[2];
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
int raggioPallina=20;
offX=this.getWidth()/2;
offY=this.getHeight()/2;
scale=(getHeight()-100)/sistema.L1/2;
ArrayList<Point2D.Double> tracciato;
synchronized(sistema){
x[0]=sistema.getX()*scale;
y[0]=-sistema.getY()*scale;
tracciato = sistema.getTracciato();
}
Graphics2D g2 = (Graphics2D)g;
g2.setStroke(new BasicStroke(3.0f));
for(int i=0; i<tracciato.size()-1; i++){
int x1 = (int) (tracciato.get(i).x*scale+offX);
int y1 = (int) (-tracciato.get(i).y*scale+offY);
int x2 = (int) (tracciato.get(i+1).x*scale+offX);
int y2 = (int) (-tracciato.get(i+1).y*scale+offY);
int c = (int) (255.0/tracciato.size()*i);
// System.out.println("i: "+i+" colore: "+c+" n."+sistema.tracciato.size()*i);
g2.setPaint(new Color(c, 0, 0));
g.drawLine(x1,y1,x2,y2);
}
g2.setPaint(new Color(0, 0, 0));
g2.setStroke(new BasicStroke(2.0f));
//bracci e palline
g.drawLine(offX,offY, (int)x[0]+offX,(int)y[0]+offY);
g.fillOval((int)x[0]-raggioPallina/2+offX, (int)y[0]-raggioPallina/2+offY, raggioPallina, raggioPallina);
//energia
g2.setStroke(new BasicStroke(1.0f));
g2.setPaint(new Color(0.5f, 0.5f, 0.5f));
g.fillRect(10,10,DIM_BARRA_EN,10);//tot
g2.setPaint(new Color(0f, 1f, 0f));
double e = sistema.energiaCinetica();
double v = sistema.energiaPotenziale();
double m = sistema.energiaIniziale;
g.fillRect(10,20,(int)(e/sistema.energiaIniziale*DIM_BARRA_EN),10);//cinetica
g2.setPaint(new Color(1f, 0f, 0f));
g.fillRect(10+(int)(e/sistema.energiaIniziale*DIM_BARRA_EN),20,
(int)(v/sistema.energiaIniziale*DIM_BARRA_EN),10);//potenziale
}
@Override
public void mouseDragged(MouseEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void mouseMoved(MouseEvent arg0) {
x[0]=(double)arg0.getX()-offX;
y[0]=(double)arg0.getY()-offY;
}
@Override
public void run() {
// TODO Auto-generated method stub
while(true){
sistema.simulate();
System.out.format("EnIni:%8.2f Tot.%8.2f = C: %8.2f P: %8.2f\n",
sistema.energiaIniziale,
sistema.energiaCinetica()+sistema.energiaPotenziale(),
sistema.energiaCinetica(),sistema.energiaPotenziale());
repaint();
try {
Thread.sleep((long) (sistema.dt*1000));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class Pendolo {
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(600, 600);
frame.setLayout(null);
Sistema s = new Sistema();
Pannello p = new Pannello(s);
p.setBounds(0,0,600,600);
frame.add(p);
p.addMouseMotionListener(p);
new Thread(p).start();
frame.setVisible(true);
}
}
现在，当我想从地图中获取特定键并修改其值时 我得到错误的第二个参数类型。实测值： 'java.lang.String中'，必需的： '？'。
请建议更新密钥值的任何方式。
答案 0 :(得分：0)
您尝试通过键xyzkey（您的类'成员）获取值，并将更改后的值放入键"xyzkey"（字符串）。因此，您需要将get更改为get("xyzkey")或将put更改为put(xyzkey, ...)。
答案 1 :(得分：0)
public void testMethod(Map<String, ?> settings) {
您在这里使用泛型通配符。 在此方法中，未定义参数的输入类型，因此您可以向地图添加任何内容（除了null ）。
找到了很好的回答here。