eclipse - java swing component cannot be resolved

Question

I took the following code from a tutorial:

import javax.swing.*;
import java.util.Date;

public class SwingGUI {

    public static void main( String[] args )
      {
        JFrame f = new JFrame( "test" );
        f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        f.setSize( 1500, 900 );
        JLabel l = new JLabel( String.format( "%tT", new Date() ) );
        f.add(l);
        f.setVisible( true );
      }
}

The f.add(l); is highlighted and two errors are shown:

• The method add(Component) in the type Container is not applicable for the arguments (JLabel)

• The type javax.swing.JComponent cannot be resolved. It is indirectly referenced from required .class files

Being relatively new to java, I do not really understand what Eclipse is trying to tell me. What can I do to make it work?

edit: The code runs without the line f.add(l);, so the problem is not that JFrame or JLabel are not found. After fiddeling around a little I got rid of the first error, but the second still remains. The component cannot be resolved, because it is indirectly referenced. What does that mean?

Answer 1

Updating the execution environment under system library to JavaSE-1.7 or JavaSE-1.8 in eclipse should solve the problem. To update the step below can be followed:

> Right-click on the project
> Select properties
> Java build path
> Library > Add Library > Add JRE SYSTEM Library
> Execution Environment
> Select JavaSE-1.7 or JavaSE-1.8
> Finish