According to specification for java.awt.BorderLayput.getLayoutComponent(Container target, Object constraints)
passed target param is "the Container using this BorderLayout", so if container that does not use this layout is passed, then null is expected to be returned
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Parameters:
    constraints - the desired absolute position, one of CENTER, one of NORTH, SOUTH, EAST, WEST
    target - the Container using this BorderLayout 
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but actually component that was passed to method addLayoutComponent(Component comp, Object constraints) using the same constraints is returned 

Here is an example:
----- Test.java ---------------------------------------------
import javax.swing.*;
import java.awt.*;

public class Test {
    public static void main(String[] args) {
        final BorderLayout borderLayout = new BorderLayout();
        final Component componentToBeAdded = new JButton();
        borderLayout.addLayoutComponent(componentToBeAdded, BorderLayout.CENTER);
        final Component returnedComponent = borderLayout.getLayoutComponent(new JPanel(), BorderLayout.CENTER);
        System.out.println("returnedComponent = " + returnedComponent);
    }
}
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  xxxxx@xxxxx   2005-04-19 13:16:54 GMT

N/A

There is no any sort of check if target Container is assigned with current instance of BorderLayout in code below. Seems that first parameter is never in use:
....
    public Component getLayoutComponent(Container target, Object constraints) {
	boolean ltr = target.getComponentOrientation().isLeftToRight();
        Component result = null;
....

  xxxxx@xxxxx   2005-04-22 11:19:54 GMT