如何從另一個類中的 void 方法調用變量

Question

如何從另一個類中的 void 方法調用字符串變量 user

我經常在運行此代碼時遇到錯誤，因為 getUser() 函數中的用戶不等於 action(ActionEvent j) 函數中的用戶。

阿爾法類：

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;
}

主要的：

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

}

}

Answer 1

這里總結了所有問題：

阿爾法類：

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;
}

主要的：

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);

}

}