jdk/src/java.desktop/share/classes/java/awt/CheckboxGroup.java

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package java.awt;

/**
 * The {@code CheckboxGroup} class is used to group together
 * a set of {@code Checkbox} buttons.
 * <p>
 * Exactly one check box button in a {@code CheckboxGroup} can
 * be in the "on" state at any given time. Pushing any
 * button sets its state to "on" and forces any other button that
 * is in the "on" state into the "off" state.
 * <p>
 * The following code example produces a new check box group,
 * with three check boxes:
 *
 * <hr><blockquote><pre>
 * setLayout(new GridLayout(3, 1));
 * CheckboxGroup cbg = new CheckboxGroup();
 * add(new Checkbox("one", cbg, true));
 * add(new Checkbox("two", cbg, false));
 * add(new Checkbox("three", cbg, false));
 * </pre></blockquote><hr>
 * <p>
 * This image depicts the check box group created by this example:
 * <p>
 * <img src="doc-files/CheckboxGroup-1.gif" alt="Shows three checkboxes,
 * arranged vertically, labeled one, two, and three. Checkbox one is in the on
 * state." style="margin: 7px 10px;">
 *
 * @author      Sami Shaio
 * @see         java.awt.Checkbox
 * @since       1.0
 */
public class CheckboxGroup implements java.io.Serializable {
    /**
     * The current choice.
     * @serial
     * @see #getCurrent()
     * @see #setCurrent(Checkbox)
     */
    Checkbox selectedCheckbox = null;

    /*
     * JDK 1.1 serialVersionUID
     */
    private static final long serialVersionUID = 3729780091441768983L;

    /**
     * Creates a new instance of {@code CheckboxGroup}.
     */
    public CheckboxGroup() {
    }

    /**
     * Gets the current choice from this check box group.
     * The current choice is the check box in this
     * group that is currently in the "on" state,
     * or {@code null} if all check boxes in the
     * group are off.
     * @return   the check box that is currently in the
     *                 "on" state, or {@code null}.
     * @see      java.awt.Checkbox
     * @see      java.awt.CheckboxGroup#setSelectedCheckbox
     * @since    1.1
     */
    public Checkbox getSelectedCheckbox() {
        return getCurrent();
    }

    /**
     * Returns the current choice from this check box group
     * or {@code null} if none of checkboxes are selected.
     *
     * @return the selected checkbox
     * @deprecated As of JDK version 1.1,
     * replaced by {@code getSelectedCheckbox()}.
     */
    @Deprecated
    public Checkbox getCurrent() {
        return selectedCheckbox;
    }

    /**
     * Sets the currently selected check box in this group
     * to be the specified check box.
     * This method sets the state of that check box to "on" and
     * sets all other check boxes in the group to be off.
     * <p>
     * If the check box argument is {@code null}, all check boxes
     * in this check box group are deselected. If the check box argument
     * belongs to a different check box group, this method does
     * nothing.
     * @param     box   the {@code Checkbox} to set as the
     *                      current selection.
     * @see      java.awt.Checkbox
     * @see      java.awt.CheckboxGroup#getSelectedCheckbox
     * @since    1.1
     */
    public void setSelectedCheckbox(Checkbox box) {
        setCurrent(box);
    }

    /**
     * Sets the currently selected check box in this group
     * to be the specified check box and unsets all others.
     *
     * @param  box the {@code Checkbox} to set as the
     *         current selection.
     * @deprecated As of JDK version 1.1,
     * replaced by {@code setSelectedCheckbox(Checkbox)}.
     */
    @Deprecated
    public synchronized void setCurrent(Checkbox box) {
        if (box != null && box.group != this) {
            return;
        }
        Checkbox oldChoice = this.selectedCheckbox;
        this.selectedCheckbox = box;
        if (oldChoice != null && oldChoice != box && oldChoice.group == this) {
            oldChoice.setState(false);
        }
        if (box != null && oldChoice != box && !box.getState()) {
            box.setStateInternal(true);
        }
    }

    /**
     * Returns a string representation of this check box group,
     * including the value of its current selection.
     * @return    a string representation of this check box group.
     */
    public String toString() {
        return getClass().getName() + "[selectedCheckbox=" + selectedCheckbox + "]";
    }

}