java一个类怎么调用另一个类的变量_如何在一个类里调用到另一个类的变量的值...
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全文，，，
写了三个类，调用那个对象为null值
三个类都不在一个包
---------------------------------------------------被调用的方法
public class CunKuan {
......
jb1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
String yue = jtf.getText();
int in = Integer.parseInt(yue);
User user = new User();
Text text = new Text();
text.link();
User_name un = new User_name(); ----new User_na
String zh_name = un.getU_name(); 从这类里提取变量的值用getU_name();方法
// 有什么方法可以调用到下面Client类中的String username 变量
//
System.out.println(un.getU_name()); ---打出来居是null值，我前面有给值的
text.deal(user, in, zh_name);
} catch (Exception e1) { }
} });
------------------------------------------------------ 一、执行第一个类
......
public class Client {
jb1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String username = jtf.getText(); //记录username ！！！ 我想把这个对象传过去
String password = jtf2.getText();
User_name un = new User_name(username); //把他放到User_name类中去，下面
System.out.println(un.getU_name()); //打印出来居是null值
User user = new User();
Text text = new Text();
text.link(); //连接数据库方法
text.read(user, username); //提取账户密码方法
String zh_name = text.getZh(); //登陆
String mm_password = text.getMm();
if (username.equals(zh_name) && password.equals(mm_password)) {
CunQu_ cq = new CunQu_();
jf.setVisible(false);
} else {
ts.setText("您输入卡号或密码错误");
}
}
});
------------------------------------------------------ 二、执行第二个类
public class Text {
......
public void deal(User user, int sum, String name_users) {
try {
System.out.println("........");
String sql_deal = "update text set balance = balance + ？ where name = ？";
ps_deal = conn.prepareStatement(sql_deal);
System.out.println(conn);
ps_deal.setInt(1, sum);
ps_deal.setString(2, name_users);
System.out.println("qqqqqqqqqq");
ps_deal.executeUpdate();
System.out.println(ps_deal.executeUpdate());
} catch (SQLException e) {
System.out.println(e + "访问数据库余额增减错误./");
} }
-------------------------------------------------------User_name类
调用这里面的变量怎么会是空值？
private String u_name；
public User_name() {
super();
} public User_name(String uName) {
super();
u_name = uName;
}
}
public String getU_name() {
return u_name;
}
public void setU_name(String uName) {
u_name = uName;
}