The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
File choosers provide a GUI for navigating the file system, and then either choosing a file or directory from a list, or entering the name of a file or directory. To display a file chooser, you usually use the JFileChooser
API to show a modal dialog containing the file chooser. Another way to present a file chooser is to add an instance of
JFileChooser
to a container.
If you intend to distribute your program as a sandbox Java Web Start application, then instead of using the JFileChooser
API you should use the file services provided by the JNLP API. These services FileOpenService
and FileSaveService
not only provide support for choosing files in a restricted environment, but also take care of actually opening and saving them. An example of using these services is in JWSFileChooserDemo. Documentation for using the JNLP API can be found in the
Java Web Start lesson.
Click the Launch button to run JWSFileChooserDemo using Java™ Web Start (download JDK 7 or later). Alternatively, to compile and run the example yourself, consult the example index.
When working with the JWSFileChooserDemo
example, be careful not to lose files that you need. Whenever you click the save button and select an existing file, this demo brings up the File Exists dialog box with a request to replace the file. Accepting the request overwrites the file.
The rest of this section discusses how to use the JFileChooser
API. A JFileChooser
object only presents the GUI for choosing files. Your program is responsible for doing something with the chosen file, such as opening or saving it. Refer to
Basic I/O for information on how to read and write files.
The JFileChooser
API makes it easy to bring up open and save dialogs. The type of look and feel determines what these standard dialogs look like and how they differ. In the Java look and feel, the save dialog looks the same as the open dialog, except for the title on the dialog's window and the text on the button that approves the operation. Here is a picture of a standard open dialog in the Java look and feel:
Here is a picture of an application called FileChooserDemo
that brings up an open dialog and a save dialog.
FileChooserDemo.java
, change the file selection mode to directories-only mode. (Search for DIRECTORIES_ONLY
and uncomment the line that contains it.) Then compile and run the example again. You will only be able to see and select directories, not ordinary files.Bringing up a standard open dialog requires only two lines of code:
//Create a file chooser final JFileChooser fc = new JFileChooser(); ... //In response to a button click: int returnVal = fc.showOpenDialog(aComponent);
The argument to the showOpenDialog
method specifies the parent component for the dialog. The parent component affects the position of the dialog and the frame that the dialog depends on. For example, the Java look and feel places the dialog directly over the parent component. If the parent component is in a frame, then the dialog is dependent on that frame. This dialog disappears when the frame is minimized and reappears when the frame is maximized.
By default, a file chooser that has not been shown before displays all files in the user's home directory. You can specify the file chooser's initial directory by using one of JFileChooser
's other constructors, or you can set the directory with the setCurrentDirectory
method.
The call to showOpenDialog
appears in the actionPerformed
method of the Open a File button's action listener:
public void actionPerformed(ActionEvent e) { //Handle open button action. if (e.getSource() == openButton) { int returnVal = fc.showOpenDialog(FileChooserDemo.this); if (returnVal == JFileChooser.APPROVE_OPTION) { File file = fc.getSelectedFile(); //This is where a real application would open the file. log.append("Opening: " + file.getName() + "." + newline); } else { log.append("Open command cancelled by user." + newline); } } ... }
The showXxxDialog
methods return an integer that indicates whether the user selected a file. Depending on how you use a file chooser, it is often sufficient to check whether the return value is APPROVE_OPTION
and then not to change any other value. To get the chosen file (or directory, if you set up the file chooser to allow directory selections), call the getSelectedFile
method on the file chooser. This method returns an instance of
File
.
The example obtains the name of the file and uses it in the log message. You can call other methods on the File
object, such as getPath
, isDirectory
, or exists
to obtain information about the file. You can also call other methods such as delete
and rename
to change the file in some way. Of course, you might also want to open or save the file by using one of the reader or writer classes provided by the Java platform. See
Basic I/O for information about using readers and writers to read and write data to the file system.
The example program uses the same instance of the JFileChooser
class to display a standard save dialog. This time the program calls showSaveDialog
:
int returnVal = fc.showSaveDialog(FileChooserDemo.this);
By using the same file chooser instance to display its open and save dialogs, the program reaps the following benefits:
Finally, the example program has commented-out lines of code that let you change the file selection mode. For example, the following line of code makes the file chooser able to select only directories, and not files:
fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
Another possible selection mode is FILES_AND_DIRECTORIES
. The default is FILES_ONLY
. The following picture shows an open dialog with the file selection mode set to DIRECTORIES_ONLY
. Note that, in the Java look and feel at least, only directories are visible not files.
If you want to create a file chooser for a task other than opening or saving, or if you want to customize the file chooser, keep reading. We will discuss the following topics:
Let us look at FileChooserDemo2
example, a modified version of the previous demo program that uses more of the JFileChooser
API. This example uses a file chooser that has been customized in several ways. Like the original example, the user invokes a file chooser with the push of a button. Here is a picture of the file chooser:
As the figure shows, this file chooser has been customized for a special task (Attach), provides a user-choosable file filter (Just Images), uses a special file view for image files, and has an accessory component that displays a thumbnail sketch of the currently selected image file.
The remainder of this section shows you the code that creates and customizes this file chooser. See the example index for links to all the files required by this example.
As you have seen, the JFileChooser
class provides the showOpenDialog
method for displaying an open dialog and the showSaveDialog
method for displaying a save dialog.
The class has another method, showDialog
, for displaying a file chooser for a custom task in a dialog. In the Java look and feel, the only difference between this dialog and the other file chooser dialogs is the title on the dialog window and the label on the approve button. Here is the code from FileChooserDemo2
that brings up the file chooser dialog for the Attach task:
JFileChooser fc = new JFileChooser(); int returnVal = fc.showDialog(FileChooserDemo2.this, "Attach");
The first argument to the showDialog
method is the parent component for the dialog. The second argument is a String
object that provides both the title for the dialog window and the label for the approve button.
Once again, the file chooser doesn't do anything with the selected file. The program is responsible for implementing the custom task for which the file chooser was created.
By default, a file chooser displays all of the files and directories that it detects, except for hidden files. A program can apply one or more file filters to a file chooser so that the chooser shows only some files. The file chooser calls the filter's accept
method for each file to determine whether it should be displayed. A file filter accepts or rejects a file based on criteria such as file type, size, ownership, and so on. Filters affect the list of files displayed by the file chooser. The user can enter the name of any file even if it is not displayed.
JFileChooser
supports three different kinds of filtering. The filters are checked in the order listed here. For example, an application-controlled filter sees only those files accepted by the built-in filtering.
setFileHidingEnabled(false)
to show hidden files.FileFilter
, instantiate it, and use the instance as an argument to the setFileFilter
method. The installed filter is displayed on the list of user-choosable filters. The file chooser shows only those files that the filter accepts.FileChooserDemo2
adds a custom file filter to the list of user-choosable filters:
fc.addChoosableFileFilter(new ImageFilter());
fc.setAcceptAllFileFilterUsed(false);
ImageFilter.java
and is a subclass of FileFilter
. The ImageFilter
class implements the getDescription
method to return "Just Images" a string to put in the list of user-choosable filters. ImageFilter
also implements the accept
method so that it accepts all directories and any file that has a .png
, .jpg
, .jpeg
, .gif
, .tif
, or .tiff
filename extension.
public boolean accept(File f) { if (f.isDirectory()) { return true; } String extension = Utils.getExtension(f); if (extension != null) { if (extension.equals(Utils.tiff) || extension.equals(Utils.tif) || extension.equals(Utils.gif) || extension.equals(Utils.jpeg) || extension.equals(Utils.jpg) || extension.equals(Utils.png)) { return true; } else { return false; } } return false; }
The preceding code sample uses the getExtension
method and several string constants from
Utils.java
, shown here:
public class Utils { public final static String jpeg = "jpeg"; public final static String jpg = "jpg"; public final static String gif = "gif"; public final static String tiff = "tiff"; public final static String tif = "tif"; public final static String png = "png"; /* * Get the extension of a file. */ public static String getExtension(File f) { String ext = null; String s = f.getName(); int i = s.lastIndexOf('.'); if (i > 0 && i < s.length() - 1) { ext = s.substring(i+1).toLowerCase(); } return ext; } }
In the Java look and feel, the chooser's list shows each file's name and displays a small icon that represents whether the file is a true file or a directory. You can customize this file view by creating a custom subclass of
FileView
and using an instance of the class as an argument to the setFileView
method. The example uses an instance of a custom class, implemented in
ImageFileView.java
, as the file chooser's file view.
fc.setFileView(new ImageFileView());
The ImageFileView
class shows a different icon for each type of image accepted by the image filter described previously.
The ImageFileView
class overrides the five abstract methods defined in the FileView
as follows.
String getTypeDescription(File f)
ImageFileView
's implementation of this method:
public String getTypeDescription(File f) { String extension = Utils.getExtension(f); String type = null; if (extension != null) { if (extension.equals(Utils.jpeg) || extension.equals(Utils.jpg)) { type = "JPEG Image"; } else if (extension.equals(Utils.gif)){ type = "GIF Image"; } else if (extension.equals(Utils.tiff) || extension.equals(Utils.tif)) { type = "TIFF Image"; } else if (extension.equals(Utils.png)){ type = "PNG Image"; } } return type; }
Icon getIcon(File f)
ImageFileView
's implementation of this method:
public Icon getIcon(File f) { String extension = Utils.getExtension(f); Icon icon = null; if (extension != null) { if (extension.equals(Utils.jpeg) || extension.equals(Utils.jpg)) { icon = jpgIcon; } else if (extension.equals(Utils.gif)) { icon = gifIcon; } else if (extension.equals(Utils.tiff) || extension.equals(Utils.tif)) { icon = tiffIcon; } else if (extension.equals(Utils.png)) { icon = pngIcon; } } return icon; }
String getName(File f)
null
to indicate that the look and feel should figure it out. Another common implementation returns f.getName()
.String getDescription(File f)
null
to indicate that the look and feel should figure it out.Boolean isTraversable(File f)
null
to indicate that the look and feel should figure it out. Some applications might want to prevent users from descending into a certain type of directory because it represents a compound document. The isTraversable
method should never return true
for a non-directory.The customized file chooser in FileChooserDemo2
has an accessory component. If the currently selected item is a PNG, JPEG, TIFF, or GIF image, the accessory component displays a thumbnail sketch of the image. Otherwise, the accessory component is empty. Aside from a previewer, probably the most common use for the accessory component is a panel with more controls on it such as check boxes that toggle between features.
The example calls the setAccessory
method to establish an instance of the ImagePreview
class, implemented in
ImagePreview.java
, as the chooser's accessory component:
fc.setAccessory(new ImagePreview(fc));
Any object that inherits from the JComponent
class can be an accessory component. The component should have a preferred size that looks good in the file chooser.
The file chooser fires a property change event when the user selects an item in the list. A program with an accessory component must register to receive these events to update the accessory component whenever the selection changes. In the example, the ImagePreview
object itself registers for these events. This keeps all the code related to the accessory component together in one class.
Here is the example's implementation of the propertyChange
method, which is the method called when a property change event is fired:
//where member variables are declared File file = null; ... public void propertyChange(PropertyChangeEvent e) { boolean update = false; String prop = e.getPropertyName(); //If the directory changed, don't show an image. if (JFileChooser.DIRECTORY_CHANGED_PROPERTY.equals(prop)) { file = null; update = true; //If a file became selected, find out which one. } else if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(prop)) { file = (File) e.getNewValue(); update = true; } //Update the preview accordingly. if (update) { thumbnail = null; if (isShowing()) { loadImage(); repaint(); } } }
If SELECTED_FILE_CHANGED_PROPERTY
is the property that changed, this method obtains a File
object from the file chooser. The loadImage
and repaint
methods use the File
object to load the image and repaint the accessory component.
The API for using file choosers falls into these categories:
Method or Constructor | Purpose |
---|---|
JFileChooser() JFileChooser(File) JFileChooser(String) |
Creates a file chooser instance. The File and String arguments, when present, provide the initial directory. |
int showOpenDialog(Component) int showSaveDialog(Component) int showDialog(Component, String) |
Shows a modal dialog containing the file chooser. These methods return APPROVE_OPTION if the user approved the operation and CANCEL_OPTION if the user cancelled it. Another possible return value is ERROR_OPTION , which means an unanticipated error occurred. |
Method | Purpose |
---|---|
void setSelectedFile(File) File getSelectedFile() |
Sets or obtains the currently selected file or (if directory selection has been enabled) directory. |
void setSelectedFiles(File[]) File[] getSelectedFiles() |
Sets or obtains the currently selected files if the file chooser is set to allow multiple selection. |
void setFileSelectionMode(int) void getFileSelectionMode() boolean isDirectorySelectionEnabled() boolean isFileSelectionEnabled() |
Sets or obtains the file selection mode. Acceptable values are FILES_ONLY (the default), DIRECTORIES_ONLY , and FILES_AND_DIRECTORIES .Interprets whether directories or files are selectable according to the current selection mode. |
void setMultiSelectionEnabled(boolean) boolean isMultiSelectionEnabled() |
Sets or interprets whether multiple files can be selected at once. By default, a user can choose only one file. |
void setAcceptAllFileFilterUsed(boolean) boolean isAcceptAllFileFilterUsed() |
Sets or obtains whether the AcceptAll file filter is used as an allowable choice in the choosable filter list; the default value is true . |
Dialog createDialog(Component) | Given a parent component, creates and returns a new dialog that contains this file chooser, is dependent on the parent's frame, and is centered over the parent. |
Method | Purpose |
---|---|
void ensureFileIsVisible(File) | Scrolls the file chooser's list such that the indicated file is visible. |
void setCurrentDirectory(File) File getCurrentDirectory() |
Sets or obtains the directory whose files are displayed in the file chooser's list. |
void changeToParentDirectory() | Changes the list to display the current directory's parent. |
void rescanCurrentDirectory() | Checks the file system and updates the chooser's list. |
void setDragEnabled(boolean) boolean getDragEnabled() |
Sets or obtains the property that determines whether automatic drag handling is enabled. See Drag and Drop and Data Transfer for more details. |
Method | Purpose |
---|---|
void setAccessory(javax.swing.JComponent) JComponent getAccessory() |
Sets or obtains the file chooser's accessory component. |
void setFileFilter(FileFilter) FileFilter getFileFilter() |
Sets or obtains the file chooser's primary file filter. |
void setFileView(FileView) FileView getFileView() |
Sets or obtains the chooser's file view. |
FileFilter[] getChoosableFileFilters() void addChoosableFileFilter(FileFilter) boolean removeChoosableFileFilter(FileFilter) void resetChoosableFileFilters() FileFilter getAcceptAllFileFilter() |
Sets, obtains, or modifies the list of user-choosable file filters. |
void setFileHidingEnabled(boolean) boolean isFileHidingEnabled() |
Sets or obtains whether hidden files are displayed. |
void setControlButtonsAreShown(boolean) boolean getControlButtonsAreShown() |
Sets or obtains the property that indicates whether the Approve and Cancel buttons are shown in the file chooser. This property is true by default. |
This table shows the examples that use file choosers and points to where those examples are described.
Example | Where Described | Notes |
---|---|---|
FileChooserDemo |
This section | Displays an open dialog and a save dialog. |
FileChooserDemo2 |
This section | Uses a file chooser with custom filtering, a custom file view, and an accessory component. |
JWSFileChooserDemo |
This section | Uses the JNLP API to open and save files. |