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package com.ceshi;
import java.awt.*;
import javax.swing.*;
public class drawline extends JFrame {
/**
* @param args
*/
drawline() {
setTitle("zhixian");
setSize(1000, 1000);
DrawComponent dp = new DrawComponent(100, 100 , 400 , 100);
add(dp);
DrawComponent dp1[] = new DrawComponent[19];
DrawComponent dp2[] = new DrawComponent[19];
for (int i = 1; i < 19; i++) {
dp1[i] = new DrawComponent( i * 50, 50, 19 * 50, i * 50);
dp2[i] = new DrawComponent(50, i * 50, i * 50, 19 * 50);
add(dp1[i]);
add(dp2[i]);
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
EventQueue.invokeLater(new Runnable() {
public void run() {
drawline dline = new drawline();
dline.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
dline.setVisible(true);
}
});
}
}
class DrawComponent extends JComponent {
DrawComponent(int a, int b, int c, int d) {
l1 = a;
l2 = b;
h1 = c;
h2 = d;
}
public void paintComponent(Graphics g) {
Graphics g2 = (Graphics) g;
g2.drawLine(l1, l2, h1, h2);
}
private int l1, l2, h1, h2;
}
DrawComponent dp1[] = new DrawComponent[19];
DrawComponent dp2[] = new DrawComponent[19];
改为
DrawComponent dp1[] = null;
DrawComponent dp2[] = null;
DrawComponent dp1[] = new DrawComponent[19];
DrawComponent dp2[] = new DrawComponent[19];
for (int i = 1; i < 19; i++) {
dp1[i] = new DrawComponent( i * 50, 50, 19 * 50, i * 50);
dp2[i] = new DrawComponent(50, i * 50, i * 50, 19 * 50);
add(dp1[i]);
add(dp2[i]);
}
就不能运行了,这段程序的问题在哪?