Tests that iterate over different input values for SpringLayout.Constraints revealed inconsistency between passed x,y springs and values returned from getY() and getX() methods in a border case.
Please see the following minimized code sample:
---
import javax.swing.*;

public class VeryMinimized {

    public static void main(String[] args) {
        final Spring y = Spring.constant(0, 0, 0);
        final Spring x = Spring.constant(0, 0, 0);
        SpringLayout.Constraints constraints =
                new SpringLayout.Constraints(
                        x,
                        y,
                        Spring.constant(0, 0, 0),
                        Spring.constant(0, 0, 0));
        constraints.setConstraint(SpringLayout.SOUTH, Spring.constant(0, 0, 0));
        constraints.setConstraint(SpringLayout.EAST, Spring.constant(0, 0, 0));
        if (constraints.getY() != y) {
            System.out.println(
                    "The y component is wrong. \n" +
                    "Expected: \"" + y + "\"\nReturned: \"" + constraints.getY() + "\""
            );
        }
        if (constraints.getX() != x) {
            System.out.println(
                    "The x component is wrong. \n" +
                    "Expected: \"" + x + "\"\nReturned: \"" + constraints.getX() + "\""
            );
        }
    }
}
---
The output will be like the following:

The y component is wrong.
Expected: "StaticSpring [0, 0, 0]"
Returned: "CompoundSpring of StaticSpring [0, 0, 0] and javax.swing.Spring$NegativeSpring@e0e1c6"
The x component is wrong.
Expected: "StaticSpring [0, 0, 0]"
Returned: "CompoundSpring of StaticSpring [0, 0, 0] and javax.swing.Spring$NegativeSpring@6ca1c"

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JCK-runtime-7 b03
JDK 7 b30
Solaris 10 amd (jck)

http://moonblade.russia.sun.com/set/java/jck/qa-results/jck/7/ea/b03/results/qac/m002_b30_failed_c1/solaris-amd64-080723150835/execdata/jtwork/report/filtered/newFailedTestCases.html

The following tests fail:

api/javax_swing/SpringLayout/Constraints/index.html#SetGet[Constraints0011]
api/javax_swing/SpringLayout/Constraints/index.html#SetGet[Constraints0009]