如何从另一个类中的 void 方法调用变量

Question

如何从另一个类中的 void 方法调用字符串变量 user

我在运行此代码时经常遇到错误，因为 getUser() 函数中的用户不等于 action(ActionEvent j) 函数中的用户。

Alpha 类：

public class Alpha(){

private string user;

public Alpha(int temp){
temp = 0;
}

public void action(ActionEvent e){
String command = e.getActionCommand();
user = "hi";
}

public String getUser(){
return this.user;
}

主要：

public class Test {
    public static void main(String[] args) {
    Alpha n = new Alpha();
    String username = n.getUser();
    System.out.println(username);

}

}

Answer 1

这里是所有问题的总结：

Alpha 类：

public class Alpha(){

private string user;

public Alpha(int temp){ why do you need a temp argument?
temp = 0; //why do you set temp at 0?
}

public void action(ActionEvent j){ // why do you need an ActionEvent j argument?
user = "hi";
}

public String getUser(){
return this.user;
}

主要：

public class Test {
    public static void main(String[] args) {
    Alpha n = new Alpha(); //you call a contructor but not the one you write -> Alpha(int temp)
    String username = n.getUser();
/** you try to get the username here but it was never set (so it = null)
    you set it in action(ActionEvent j), so you can try to insert
    action(j);
**/
    System.out.println(username);

}

}