Platforms: reproduced - Windows, Solaris
JDK: 6, 7

Assertions in the specification of the following method are not satisfied
http://download.oracle.com/javase/7/docs/api/javax/swing/text/DefaultCaret.html#setVisible(boolean)

Specification says:
 Setting it to false turns it completely off. 
 To determine whether the blinking is active, you should call isActive. 
 In effect, isActive is an appropriate corresponding "getter" method for this one.

Here's a list showing the potential return values of both isActive and isVisible after calling this method:
 setVisible(true):
    isActive(): true
    isVisible(): true or false depending on whether or not the caret is blinked on or off
 setVisible(false):
    isActive(): false
    isVisible(): false 


The latter statement is not satisfied always. The code sample below shows that setVisible(false) behaves more like setVisible(true)


import javax.swing.*;
import javax.swing.text.DefaultCaret;
import javax.swing.text.JTextComponent;
import java.lang.reflect.InvocationTargetException;

public class CaretInvisible {

    public static void main(String[] args) throws InvocationTargetException, InterruptedException {
        final DefaultCaret caret = new DefaultCaret();
        final JFrame[] jFrame = new JFrame[1];

        SwingUtilities.invokeAndWait(new Runnable() {
            @Override
            public void run() {

                JTextComponent comp = new javax.swing.JTextArea(10, 10);
                jFrame[0] = new JFrame();
                jFrame[0].getContentPane().add(comp);

                jFrame[0].pack();
                jFrame[0].setVisible(true);
                jFrame[0].toFront();


                comp.setCaret(caret);

                caret.setBlinkRate(300);
                caret.setVisible(false);
            }
        });

        for (int i=0; i<20; i++) {
            Thread.sleep(100);
            System.out.println("caret.isVisible() = " + caret.isVisible());
            System.out.println("caret.isActive() = " + caret.isActive());
        }

        SwingUtilities.invokeAndWait(new Runnable() {
            @Override
            public void run() {
                jFrame[0].dispose();
            }
        });

    }
}

The output will be:

caret.isVisible() = false
caret.isActive() = false
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = false
caret.isActive() = true
caret.isVisible() = true
caret.isActive() = true


It could be seen that isActive() always return true, while isVisible() is dependant of the caret blinking state.
Looks like the specification misses some important assertions.
Specification says:
 In effect, isActive is an appropriate corresponding "getter" method for this one [setVisible()].

This is not satisfied as well, the following code will print out:

        final DefaultCaret caret = new DefaultCaret();
        caret.setVisible(true);
        System.err.println("caret.isActive() = " + caret.isActive());

caret.isActive() = false