下面两种定义变量的方法为什么会导致本质上的不同呢？

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下面两种定义变量的方法为什么会导致本质上的不同呢？0

这是一个简单的聊天系统模型：
ChatClient.java
<code>import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class ChatClient extends Frame {

TextField input = new TextField();
TextArea display = new TextArea();
Socket s = null;
boolean bConnected = false;
DataOutputStream dos = null;
DataInputStream dis = null;

public static void main(String[] args) {
new ChatClient().launchFrame();
}

// 定义创建窗体方法
public void launchFrame() {
setLocation(768, 384);
setSize(400, 300);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
input.addActionListener(new InputListener());
add(input, BorderLayout.SOUTH);
add(display, BorderLayout.NORTH);
pack();
setResizable(false);
setVisible(true);
connect();
new Thread(new RecvThread()).start();

}

// 创建方法，连接到服务器
public void connect() {
try {
s = new Socket("127.0.0.1", 3000);
bConnected = true;
dos = new DataOutputStream(s.getOutputStream());
dis = new DataInputStream(s.getInputStream());
} catch (IOException e) {
e.printStackTrace();
}
}

// 监听器类，用于监听输入框动作
private class InputListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
String str = input.getText().trim();
// display.setText(str);
input.setText("");
try {
dos.writeUTF(str);
dos.flush();
} catch (IOException e1) {
e1.printStackTrace();
}
}

}

// 新建线程类来接受服务器发送过来的数据
private class RecvThread implements Runnable {

public void run() {
try {
while (bConnected) {
String str = dis.readUTF();
// System.out.println("客户端发送的数据："+str);
display.setText(str);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}</code>

ChatServer.java
第一种：
<code>import java.io.*;
import java.net.*;
import java.util.*;

public class ChatServer {
// 用集合将客户端对象保存起来
List<Client> clients = new ArrayList<Client>();
DataInputStream dis = null;
DataOutputStream dos = null;
boolean bConnected = false;
    Socket s =null;
    boolean started = false;

public static void main(String[] args) {
new ChatServer().start();
}

// 创建启动方法
public void start() {
try {
ServerSocket ss = new ServerSocket(3000);
started = true;
// 循环，不断接受来自客户端的连接
while (started) {
s = ss.accept();
// 测试
System.out.println("a client connected!!!");
//bConnected = true;
Client c = new Client(s);
new Thread(c).start();
clients.add(c);
}
} catch (IOException e) {
e.printStackTrace();
}
}

// 定义线程类，处理多个连接
private class Client implements Runnable {
private Socket s;
// 构造器为s赋值
public Client(Socket s) {
this.s = s;
try {
dos = new DataOutputStream(s.getOutputStream());
dis = new DataInputStream(s.getInputStream());
bConnected = true;
} catch (IOException e) {
e.printStackTrace();
}
}

// 发送信息到客户端的方法
private void send(String str) {
try {
dos.writeUTF(str);
dos.flush();
} catch (IOException e) {
e.printStackTrace();
}
}

// 启动线程
public void run() {
try {
while (bConnected) {
String str = dis.readUTF();
for (int i = 0; i < clients.size(); i++) {
Client c = clients.get(i);
c.send(str);
}
}
} catch (IOException e) {
e.printStackTrace();
}

}
}
}</code>

第二种：
<code>import java.io.*;
import java.net.*;
import java.util.*;

public class ChatServer {
// 用集合将客户端对象保存起来
List<Client> clients = new ArrayList<Client>();
DataInputStream dis = null;
DataOutputStream dos = null;
boolean bConnected = false;
    Socket s =null;
    boolean started = false;

public static void main(String[] args) {
new ChatServer().start();
}

// 创建启动方法
public void start() {
try {
ServerSocket ss = new ServerSocket(3000);
started = true;
// 循环，不断接受来自客户端的连接
while (started) {
s = ss.accept();
// 测试
System.out.println("a client connected!!!");
//bConnected = true;
Client c = new Client(s);
new Thread(c).start();
clients.add(c);
}
} catch (IOException e) {
e.printStackTrace();
}
}

// 定义线程类，处理多个连接
private class Client implements Runnable {
private Socket s;
/* private DataOutputStream dos;
    private DataInputStream dis ; */
// 构造器为s赋值
public Client(Socket s) {
this.s = s;
try {
dos = new DataOutputStream(s.getOutputStream());
dis = new DataInputStream(s.getInputStream());
bConnected = true;
} catch (IOException e) {
e.printStackTrace();
}
}

// 发送信息到客户端的方法
private void send(String str) {
try {
dos.writeUTF(str);
dos.flush();
} catch (IOException e) {
e.printStackTrace();
}
}

// 启动线程
public void run() {
try {
while (bConnected) {
String str = dis.readUTF();
for (int i = 0; i < clients.size(); i++) {
Client c = clients.get(i);
c.send(str);
}
}
} catch (IOException e) {
e.printStackTrace();
}

}
}
}</code>