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.
In each of the following questions, choose the layout manager(s) most naturally suited for the described layout. Assume that the container controlled by the layout manager is a JPanel
.
Question 1. The container has one component that should take up as much space as possible
a. BorderLayout
b. GridLayout
c. GridBagLayout
d. a and b
e. b and c
Answer 1: d. BorderLayout
and GridLayout
easily deal with this situation. Although you could use GridBagLayout
, it's much more complex than necessary.
Question 2. The container has a row of components that should all be displayed at the same size, filling the container’s entire area.
a. FlowLayout
b. GridLayout
c. BoxLayout
d. a and b
Answer 2: b. This type of same-size layout — whether in a row, a column, or a grid — is what GridLayout
is best at.
Question 3. The container displays a number of components in a column, with any extra space going between the first two components.
a. FlowLayout
b. BoxLayout
c. GridLayout
d. BorderLayout
Answer 3: b. BoxLayout
lays out components in either a column or a row. You can specify extra space using an invisible component.
Question 4. The container can display three completely different components at different times, depending perhaps on user input or program state. Even if the components’ sizes differ, switching from one component to the next shouldn’t change the amount of space devoted to the component.
a. SpringLayout
b. BoxLayout
c. CardLayout
d. GridBagLayout
Answer 4: c. CardLayout
exists to allow components to share the same space. Although it's simpler to use a JTabbedPane
component to control an area, CardLayout
is the solution when you don't want tabs.
Exercise 1. Implement the layout described and shown in question 1.
Answer 1: See Layout1.java
. Here's the code that implements the layout:
JPanel p = new JPanel(new BorderLayout()); p.add(createComponent("Component 1"), BorderLayout.CENTER); frame.setContentPane(p);
Exercise 2. Implement the layout described and shown in question 2.
Answer 2: See Layout2.java
. Here's the code that implements the layout:
JPanel p = new JPanel(new GridLayout(1,0)); p.add(createComponent("Component 1")); p.add(createComponent("Component 2")); p.add(createComponent("Component 3")); p.add(createComponent("Component 4")); frame.setContentPane(p);
Exercise 3. Implement the layout described and shown in question 3.
Answer 3: See Layout3.java
. Here's the code that implements the layout:
JPanel p = new JPanel(); p.setLayout(new BoxLayout(p, BoxLayout.PAGE_AXIS)); p.add(createComponent("Component 1")); p.add(Box.createVerticalGlue()); p.add(createComponent("Component 2")); p.add(createComponent("Component 3")); p.add(createComponent("Component 4")); frame.setContentPane(p);
Exercise 4. Implement the layout described and shown in question 4.
Answer 4: See Layout4.java
. Here's the code that implements the layout:
...//Where the radio buttons are set up: for (int i= 0; i < strings.length; i++) { ... rb[i].setActionCommand(String.valueOf(i)); ... } ...//Where the panel to contain the shared-space components is set up: cards = new JPanel(new CardLayout()); for (int i = 0; i < strings.length; i++) { cards.add(createComponent(strings[i]), String.valueOf(i)); } ...//In the action listener for the radio buttons: public void actionPerformed(ActionEvent evt) { CardLayout cl = (CardLayout)(cards.getLayout()); cl.show(cards, (String)evt.getActionCommand()); }
Exercise 5. By adding a single line of code, make the program you wrote for Exercise 2 display the components from right-to-left, instead of from left-to-right.
Answer 5: You can change the horizontal orientation using the
setComponentOrientation
method defined by the Component
class. For example:
p.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);