这是从马士兵哪看得资料,执行时会抛出这个异常。听别人说使用遍历方法(增强的for循环)时不能改变容器内容,可为什么用for循环就可以呢?
求解import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;
public class TankClient extends Frame {
public static final int GAME_WIDTH = 800;
public static final int GAME_HEIGHT = 600;
List<Missile> ms = new ArrayList<Missile>();
Tank myTank = new Tank(50, 50,this);
Image offScreenImage = null;
public void paint(Graphics g) {
for(Missile item : ms){
item.draw(g);
}
//for(int i=0; i<ms.size(); i++) {
//Missile m = ms.get(i);
//m.draw(g);} myTank.draw(g);
}
public void update(Graphics g) {
if(offScreenImage == null) {
offScreenImage = this.createImage(GAME_WIDTH, GAME_HEIGHT);
}
Graphics gOffScreen = offScreenImage.getGraphics();
Color c = gOffScreen.getColor();
gOffScreen.setColor(Color.GREEN);
gOffScreen.fillRect(0, 0, GAME_WIDTH, GAME_HEIGHT);
gOffScreen.setColor(c);
paint(gOffScreen);
g.drawImage(offScreenImage, 0, 0, null);
} public void lauchFrame() {
this.setLocation(100,100);
this.setSize(GAME_WIDTH, GAME_HEIGHT);
this.setTitle("TankWar");
this.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
this.setResizable(false);
this.setBackground(Color.GREEN);
this.addKeyListener(new KeyMonitor());
setVisible(true);
new Thread(new PaintThread()).start();
} public static void main(String[] args) {
TankClient tc = new TankClient();
tc.lauchFrame();
}
private class PaintThread implements Runnable { public void run() {
while(true) {
repaint();
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class KeyMonitor extends KeyAdapter { public void keyPressed(KeyEvent e) {
myTank.keyPressed(e);
}
public void keyReleased(KeyEvent e){
myTank.released(e);
}
}
}
import java.awt.*;
import java.awt.event.*;public class Tank {
public static final int XSPEED = 5;
public static final int YSPEED = 5;
public static final int WIDTH = 30;
public static final int HEIGHT = 30;
int x, y;
private boolean bL=false, bU=false, bR=false, bD = false;
enum Direction {L, LU, U, RU, R, RD, D, LD, STOP};
TankClient tc;
private Direction dir = Direction.STOP;
private Direction ptDir = Direction.U;
public Tank(int x, int y,TankClient tcIn) {
this.x = x;
this.y = y;
tc = tcIn;
}
public void draw(Graphics g) {
g.setColor(Color.BLACK);
g.drawString("Pao dan counter"+tc.ms.size(),50, 50);
Color c = g.getColor();
g.setColor(Color.RED);
g.fillOval(x, y, 30, 30);
g.setColor(c);
switch(ptDir) {
case L:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x, y + Tank.HEIGHT/2);
break;
case LU:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x, y);
break;
case U:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH/2, y);
break;
case RU:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH, y);
break;
case R:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH, y + Tank.HEIGHT/2);
break;
case RD:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH, y + Tank.HEIGHT);
break;
case D:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH/2, y + Tank.HEIGHT);
break;
case LD:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x, y + Tank.HEIGHT);
break;
}
move();
}
void move() {
switch(dir) {
case L:
x -= XSPEED;
break;
case LU:
x -= XSPEED;
y -= YSPEED;
break;
case U:
y -= YSPEED;
break;
case RU:
x += XSPEED;
y -= YSPEED;
break;
case R:
x += XSPEED;
break;
case RD:
x += XSPEED;
y += YSPEED;
break;
case D:
y += YSPEED;
break;
case LD:
x -= XSPEED;
y += YSPEED;
break;
case STOP:
break;
}
if(dir!=Direction.STOP){
ptDir = dir;
}
}
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
switch(key) {
case KeyEvent.VK_CONTROL:
fire();
break;
case KeyEvent.VK_LEFT :
bL = true;
break;
case KeyEvent.VK_UP :
bU = true;
break;
case KeyEvent.VK_RIGHT :
bR = true;
break;
case KeyEvent.VK_DOWN :
bD = true;
break;
}
locateDirection();
}
void locateDirection() {
if(bL && !bU && !bR && !bD) dir = Direction.L;
else if(bL && bU && !bR && !bD) dir = Direction.LU;
else if(!bL && bU && !bR && !bD) dir = Direction.U;
else if(!bL && bU && bR && !bD) dir = Direction.RU;
else if(!bL && !bU && bR && !bD) dir = Direction.R;
else if(!bL && !bU && bR && bD) dir = Direction.RD;
else if(!bL && !bU && !bR && bD) dir = Direction.D;
else if(bL && !bU && !bR && bD) dir = Direction.LD;
else if(!bL && !bU && !bR && !bD) dir = Direction.STOP;
}
public void released(KeyEvent e){
int key = e.getKeyCode();
switch(key) {
case KeyEvent.VK_LEFT :
bL = false;
break;
case KeyEvent.VK_UP :
bU = false;
break;
case KeyEvent.VK_RIGHT :
bR = false;
break;
case KeyEvent.VK_DOWN :
bD = false;
break;
}
locateDirection();
}
public void fire(){
Missile m = new Missile(x,y,ptDir,tc);
tc.ms.add(m);
}
}
import java.awt.*;
public class Missile {
int x,y;
private final int XSPEED,YSPEED;
Tank.Direction dM;
TankClient tc;
public Missile(int xIn,int yIn,Tank.Direction dMIn,TankClient tcIn){
x = xIn;
y = yIn;
dM = dMIn;
XSPEED = 10;
YSPEED = 10;
tc = tcIn;
}
public void draw(Graphics g){
g.setColor(Color.BLACK);
g.fillOval(x, y, 10,10);
move();
}
void move(){
switch(dM) {
case L:
x -= XSPEED;
break;
case LU:
x -= XSPEED;
y -= YSPEED;
break;
case U:
y -= YSPEED;
break;
case RU:
x += XSPEED;
y -= YSPEED;
break;
case R:
x += XSPEED;
break;
case RD:
x += XSPEED;
y += YSPEED;
break;
case D:
y += YSPEED;
break;
case LD:
x -= XSPEED;
y += YSPEED;
break;
case STOP:
break;
}if(x < 0 || y < 0 || x > TankClient.GAME_WIDTH || y > TankClient.GAME_HEIGHT) {
tc.ms.remove(this);
}
}}
求解import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;
public class TankClient extends Frame {
public static final int GAME_WIDTH = 800;
public static final int GAME_HEIGHT = 600;
List<Missile> ms = new ArrayList<Missile>();
Tank myTank = new Tank(50, 50,this);
Image offScreenImage = null;
public void paint(Graphics g) {
for(Missile item : ms){
item.draw(g);
}
//for(int i=0; i<ms.size(); i++) {
//Missile m = ms.get(i);
//m.draw(g);} myTank.draw(g);
}
public void update(Graphics g) {
if(offScreenImage == null) {
offScreenImage = this.createImage(GAME_WIDTH, GAME_HEIGHT);
}
Graphics gOffScreen = offScreenImage.getGraphics();
Color c = gOffScreen.getColor();
gOffScreen.setColor(Color.GREEN);
gOffScreen.fillRect(0, 0, GAME_WIDTH, GAME_HEIGHT);
gOffScreen.setColor(c);
paint(gOffScreen);
g.drawImage(offScreenImage, 0, 0, null);
} public void lauchFrame() {
this.setLocation(100,100);
this.setSize(GAME_WIDTH, GAME_HEIGHT);
this.setTitle("TankWar");
this.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
this.setResizable(false);
this.setBackground(Color.GREEN);
this.addKeyListener(new KeyMonitor());
setVisible(true);
new Thread(new PaintThread()).start();
} public static void main(String[] args) {
TankClient tc = new TankClient();
tc.lauchFrame();
}
private class PaintThread implements Runnable { public void run() {
while(true) {
repaint();
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class KeyMonitor extends KeyAdapter { public void keyPressed(KeyEvent e) {
myTank.keyPressed(e);
}
public void keyReleased(KeyEvent e){
myTank.released(e);
}
}
}
import java.awt.*;
import java.awt.event.*;public class Tank {
public static final int XSPEED = 5;
public static final int YSPEED = 5;
public static final int WIDTH = 30;
public static final int HEIGHT = 30;
int x, y;
private boolean bL=false, bU=false, bR=false, bD = false;
enum Direction {L, LU, U, RU, R, RD, D, LD, STOP};
TankClient tc;
private Direction dir = Direction.STOP;
private Direction ptDir = Direction.U;
public Tank(int x, int y,TankClient tcIn) {
this.x = x;
this.y = y;
tc = tcIn;
}
public void draw(Graphics g) {
g.setColor(Color.BLACK);
g.drawString("Pao dan counter"+tc.ms.size(),50, 50);
Color c = g.getColor();
g.setColor(Color.RED);
g.fillOval(x, y, 30, 30);
g.setColor(c);
switch(ptDir) {
case L:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x, y + Tank.HEIGHT/2);
break;
case LU:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x, y);
break;
case U:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH/2, y);
break;
case RU:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH, y);
break;
case R:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH, y + Tank.HEIGHT/2);
break;
case RD:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH, y + Tank.HEIGHT);
break;
case D:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x + Tank.WIDTH/2, y + Tank.HEIGHT);
break;
case LD:
g.drawLine(x + Tank.WIDTH/2, y + Tank.HEIGHT/2, x, y + Tank.HEIGHT);
break;
}
move();
}
void move() {
switch(dir) {
case L:
x -= XSPEED;
break;
case LU:
x -= XSPEED;
y -= YSPEED;
break;
case U:
y -= YSPEED;
break;
case RU:
x += XSPEED;
y -= YSPEED;
break;
case R:
x += XSPEED;
break;
case RD:
x += XSPEED;
y += YSPEED;
break;
case D:
y += YSPEED;
break;
case LD:
x -= XSPEED;
y += YSPEED;
break;
case STOP:
break;
}
if(dir!=Direction.STOP){
ptDir = dir;
}
}
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
switch(key) {
case KeyEvent.VK_CONTROL:
fire();
break;
case KeyEvent.VK_LEFT :
bL = true;
break;
case KeyEvent.VK_UP :
bU = true;
break;
case KeyEvent.VK_RIGHT :
bR = true;
break;
case KeyEvent.VK_DOWN :
bD = true;
break;
}
locateDirection();
}
void locateDirection() {
if(bL && !bU && !bR && !bD) dir = Direction.L;
else if(bL && bU && !bR && !bD) dir = Direction.LU;
else if(!bL && bU && !bR && !bD) dir = Direction.U;
else if(!bL && bU && bR && !bD) dir = Direction.RU;
else if(!bL && !bU && bR && !bD) dir = Direction.R;
else if(!bL && !bU && bR && bD) dir = Direction.RD;
else if(!bL && !bU && !bR && bD) dir = Direction.D;
else if(bL && !bU && !bR && bD) dir = Direction.LD;
else if(!bL && !bU && !bR && !bD) dir = Direction.STOP;
}
public void released(KeyEvent e){
int key = e.getKeyCode();
switch(key) {
case KeyEvent.VK_LEFT :
bL = false;
break;
case KeyEvent.VK_UP :
bU = false;
break;
case KeyEvent.VK_RIGHT :
bR = false;
break;
case KeyEvent.VK_DOWN :
bD = false;
break;
}
locateDirection();
}
public void fire(){
Missile m = new Missile(x,y,ptDir,tc);
tc.ms.add(m);
}
}
import java.awt.*;
public class Missile {
int x,y;
private final int XSPEED,YSPEED;
Tank.Direction dM;
TankClient tc;
public Missile(int xIn,int yIn,Tank.Direction dMIn,TankClient tcIn){
x = xIn;
y = yIn;
dM = dMIn;
XSPEED = 10;
YSPEED = 10;
tc = tcIn;
}
public void draw(Graphics g){
g.setColor(Color.BLACK);
g.fillOval(x, y, 10,10);
move();
}
void move(){
switch(dM) {
case L:
x -= XSPEED;
break;
case LU:
x -= XSPEED;
y -= YSPEED;
break;
case U:
y -= YSPEED;
break;
case RU:
x += XSPEED;
y -= YSPEED;
break;
case R:
x += XSPEED;
break;
case RD:
x += XSPEED;
y += YSPEED;
break;
case D:
y += YSPEED;
break;
case LD:
x -= XSPEED;
y += YSPEED;
break;
case STOP:
break;
}if(x < 0 || y < 0 || x > TankClient.GAME_WIDTH || y > TankClient.GAME_HEIGHT) {
tc.ms.remove(this);
}
}}
解决方案 »
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