删除子弹，避免内存泄漏

src/main/java/com/example/tankbattle/Bullet.java

@@ -9,13 +9,19 @@ public class Bullet {
     private int x, y;
     private Dir dir;
 
-    public Bullet(int x, int y, Dir dir) {
+    public boolean live = true;
+
+    private TankFrame tf;
+
+    public Bullet(int x, int y, Dir dir, TankFrame tf) {
         this.x = x;
         this.y = y;
         this.dir = dir;
+        this.tf = tf;
     }
 
     public void paint(Graphics g) {
+        if (!live) tf.bullets.remove(this);
         Color c = g.getColor();
         g.setColor(Color.RED);
         g.fillOval(x, y, WIDTH, HEIGHT);
@@ -41,5 +47,7 @@ public class Bullet {
             default:
                 break;
         }
+
+        if (x < 0 || y < 0 || x > TankFrame.GAME_WIDTH || y > TankFrame.GAME_HEIGHT) live = false;
     }
 }

src/main/java/com/example/tankbattle/Tank.java

@@ -67,6 +67,6 @@ public class Tank {
     }
 
     public void fire(){
-        tf.bullets.add(new Bullet(this.x, this.y, this.dir));
+        tf.bullets.add(new Bullet(this.x, this.y, this.dir, this.tf));
     }
 }

src/main/java/com/example/tankbattle/TankFrame.java

@@ -9,13 +9,13 @@ import java.awt.event.KeyEvent;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 
 public class TankFrame extends Frame {
 
     Tank myTank = new Tank(200, 200, Dir.DOWN, this);
-    Bullet b = new Bullet(300, 300, Dir.DOWN);
-    private static final int GAME_WIDTH = 800,GAME_HEIGHT=600;
+    public static final int GAME_WIDTH = 800,GAME_HEIGHT=600;
 
     List<Bullet> bullets = new ArrayList<>();
 
@@ -50,11 +50,19 @@ public class TankFrame extends Frame {
 
     @Override
     public void paint(Graphics g) {
+        Color c = g.getColor();
+        g.setColor(Color.WHITE);
+        g.drawString("子弹的数量" + bullets.size(), 10, 60);
+        g.setColor(c);
+
         myTank.paint(g);
-        b.paint(g);
-        for (Bullet bullet1 : bullets) {
-            bullet1.paint(g);
+        for (int i = 0; i < bullets.size(); i++) {
+            bullets.get(i).paint(g);
         }
+//        for (Iterator<Bullet> it = bullets.iterator(); it.hasNext()) {
+//            Bullet b = it.next();
+//            if (!b.live) it.remove();
+//        }
     }