AWT

[Arun Pai]

 import java.awt.*; 
 public class TestFrame extends Frame 
 { 
      Button bNorth = new Button("North"); 
      Button bSouth = new Button("South"); 
      Button bEast = new Button("East"); 
      Button bWest = new Button("West"); 
      Button bCenter = new Button("Center"); 
      public TestFrame() 
      { 
           setLayout(new FlowLayout()); 
           add(bNorth); 
           add(bSouth); 
           add(bWest); 
           add(bEast); 
           add(bCenter); 
           setLayout(new BorderLayout()); 
           validate(); 
           setSize(300,300); 
           setVisible(true); 
      } 
      public static void main(String args[]) 
      { 
           TestFrame tf = new TestFrame(); 
      } 
 }
 

Attemping to compile and run the above code

1.Will cause a compilation error - a Layout cannot be set after a component has been added with a preset Layout Manager.
2.Will cause a Runtime Exception - a Layout cannot be set after a component has been added with a preset Layout Manager.
3.Will compile cleanly and throw no runtime Exception. Only the button with label "Center" is visible and occupies the whole screen.
4.Will compile cleanly an throw no runtime Exception. All the buttons are arranged in a single line. Any other component added in future will follow the rules of the BorderLayout Manager.
5.Will compile and run cleanly, but no component is visible.
6.Will compile cleanly and throw no runtime Exception. The buttons are arranged as listed below
Button Label Position
Center Center
North North
South South
East East
West West
ans is 5, why the component is not displayed?
-Arun

[Jose Botella]

BorderLayout and CardLayout are the uniques AWT LayoutManagers that don't know how to rearrange components previously added.