How To Know JButton Is Clicked In Another Class

I have two classes one is called main.java another is called Gui.java

in gui.java, will create a JFrame and some component.here is some code in main.java.

Java Code:

public static void main(String[] args){
while(true)//will always loop once user close the window
Gui gui = new Gui();
gui.setVisible();
if()//at here need to determine button in Gui.java is press or not to process the user input
{
String fromUser = gui.Jusertxt.getText();
}

} mh_sh_highlight_all('java');

what is the code need to use to know Button in Gui.java is clicked or not? i try use method to return true value, but in not working.