Assignment 2 Naming policy Stack Trace

Uppsala University

Assignment 2 ƒ ƒ ƒ ƒ ƒ

Actions Internationalization (I18N) Progress Icons Resize

@ UU/IT

2008-01-30 | #1

Uppsala University

Naming policy ƒ getLastName() ƒ setMaxOfLines(int i) ƒ String longName = ”foo”; ƒ int loopCounter = 7;

@ UU/IT

2008-01-30 | #2

Uppsala University

Stack Trace java.lang.NullPointerException at se.uu.it110.icqui.IcqClient.setStatus(IcqClient.java:102) at se.uu.it110.icqui.IcqUI$15.actionPerformed(IcqUI.java:343) at javax.swing.JComboBox.fireActionEvent(JComboBox.java:654) at javax.swing.JComboBox.selectedItemChanged(JComboBox.java:678) at javax.swing.JComboBox.contentsChanged(JComboBox.java:730) at javax.swing.AbstractListModel.fireContentsChanged(AbstractListMode.ja va:82) at javax.swing.DefaultComboBoxModel.setSelectedItem(DefaultComboBox Model .java:90) at javax.swing.JComboBox.setSelectedItem(JComboBox.java:377) at javax.swing.JComboBox.setSelectedIndex(JComboBox.java:414) at ...

@ UU/IT

2008-01-30 | #3

1

Uppsala University

Quality result ƒ Few lines of code is easier to read, maintain, understand etc. ƒ Less code means you see more of the program per page

@ UU/IT

2008-01-30 | #4

Uppsala University

Code style // too much code private JPanel getFilePanel() { JPanel p = new JPanel(); JScrollPane s = new JScrollPane(fileTable); p.add(s); return p; } // compact is better private JPanel getFilePanel() { JPanel p = new JPanel(); p.add(new JScrollPane(fileTable)); return p; } @ UU/IT

2008-01-30 | #5

Uppsala University

Compact // method, 1 line public String getColumnName(int col) { return headers[col]; }

// construktor FileModel(User user) { this.user = user; }

// simple test if (test == true) return; // vs. if (test) return;

@ UU/IT

2008-01-30 | #6

2

Uppsala University

javax.swing.Action ƒ Interface, contains • Accelerator, Mnemonic, Name, Icon, Description (short+long), Enabled?, command

ƒ javax.swing.AbstractAction • default implementations for the Action interface

ƒ new JButton(new ExitAction()); ƒ new JButton(new ExitAction(initValue));

@ UU/IT

2008-01-30 | #7

Uppsala University

Action – example Action playAction = new AbstractAction(“Play", new ImageIcon(“play.gif")) { public void actionPerformed(AE e) { move(“left”); } }; JButton b = new JButton(playAction); JMenuItem menuItem = commandMenu.add(playAction); playAction.setEnabled(false); @ UU/IT

2008-01-30 | #8

Uppsala University

Action ƒ The previous example is not good enough; we also need: • mnemonic, description, … • I18n • …

@ UU/IT

2008-01-30 | #9

3

Uppsala University

I18N ƒ See build.xml, target “run” File: player/ui/lang.properties: ui.ok = Ok ui.cancel = Cancel File: player/ui/lang_sv.properties: ui.ok = Okej ui.cancel = Avbryt ResourceBundle rb = ResourceBundle.getBundle(“player.ui.lang”); String okString = rb.getString(“ui.ok”); JButton okButton = new JButton(okString); @ UU/IT

2008-01-30 | #10

Uppsala University

java.util.ResourceBundle ƒ Be specific and clear! Like this; ui.menu.exit.name ui.menu.exit.mne

= Exit = x

ƒ Not like this: exit=Exit

@ UU/IT

2008-01-30 | #11

Uppsala University

Icons URL u = Player1.class.getResource("exit.gif"); JButton exitButton = new JButton(new ImageIcon(u)); ƒ At runtime, exit.gif must be located next to Player1.class ƒ Icons also need to be in CVS • Location, next to source code

ƒ Binary files need extra flag ƒ cvs add –kb binary.gif

@ UU/IT

2008-01-30 | #12

4

Uppsala University

Collections ƒ Eckel: chapter Collections of Objects • Read about containers, skip arrays

ƒ List – stores objects in sequence ƒ Set – stores unique objects in a space ƒ Map – manages key/value pairs

@ UU/IT

2008-01-30 | #13

Uppsala University

Iterators ƒ Abstraction, you don’t care about the storage ƒ Iterators are “lightweight” and do not consume a lot of resources Iterator it = collection.iterator(); while (it.hasNext()) { Object o = it.next(); } @ UU/IT

2008-01-30 | #14

Uppsala University

Iterator, exemple public List getNames(Collection col) { Vector names = new Vector(); Iterator it = col.iterator(); while (it.hasNext()) { String name = ((Person)it.next()).getName(); names.add(name); } return names; } @ UU/IT

2008-01-30 | #15

5

Uppsala University

Map import java.util.*; class Counter { int i = 1; public String toString() {return Integer.toString(i);} } class Statistics { public static void main(String[] args) { HashMap ht = new HashMap(); for (int i = 0; i < 10000; i++) { Integer r = new Integer((int)(Math.random() * 20)); if (ht.containsKey(r)) ((Counter)ht.get(r)).i++; else ht.put(r, new Counter()); } System.out.println(ht); } } @ UU/IT

2008-01-30 | #16

Uppsala University

Collections public class Log { private static final int MAX = 1000; private Map map = new HashMap(); private List list = new Vector(); private Set set = new HashSet(); Log() { Random rnd = new Random(); for (int i = 0; i < 10; i++) { map.put(new Integer((int)(System.currentTimeMillis() % MAX)), "foo"); list.add(new Integer(rnd.nextInt(MAX))); set.add(new Integer(rnd.nextInt(MAX))); } dump(map.keySet()); dump(list); dump(set); } public void dump(Collection c) { Iterator iterator = c.iterator(); System.out.println("\n" + "Collection: " + c); while (iterator.hasNext()) { System.out.println("" + iterator.next()); } } public static void main(String[] argv){ Log l = new Log(); } } @ UU/IT

2008-01-30 | #17

Uppsala University

SortedSet // create a sorted set SortedSet s = new TreeSet(); s.add("string1"); s.add("STRING2"); s.add("STRING3"); s.add("string4"); s.add("STRING5"); // get a subset of the set and display it Set sub = s.subSet("A", "ZZZZZZ"); Iterator i = sub.iterator(); while (i.hasNext()) { System.out.println(i.next()); } System.out.println(); // remove an element from the original set s.remove("STRING3"); // display the subset again i = sub.iterator(); while (i.hasNext()) { System.out.println(i.next()); } @ UU/IT

2008-01-30 | #18

6

Uppsala University

Inner class public class Foo { int i; public class Bar { int k = i; } void test() { A a = new A(); B b = new B(); } }

@ UU/IT

2008-01-30 | #19

Uppsala University

Inner classes, upcasting interface Bills { int getNoOf100(); } public class ATM { public Bills getBillStatus() { return new S(); } // we only have 500! private class S implements Bills { public int getNoOf100() { return 0; } public int get500() { return 42; } } }

@ UU/IT

2008-01-30 | #20

Uppsala University

Inner classes, anonymous interface Bills { int getNoOf100(); } public class ATM { public Bills getBillStatus() { return new Bills() { public int getNoOf100(){ return 0; } }; }; } @ UU/IT

2008-01-30 | #21

7

Uppsala University

Is there a difference? interface Bills { int get100(); } Bills s1 = new Bills() { public int get100() { return 0; } }; class Foo implements Bills { public int get100() { return 0; } } Bills s2 = new Foo(); @ UU/IT

2008-01-30 | #22

Uppsala University

Scope for inner class ƒ If you’re defining an anonymous inner class and want to use an object that’s defined outside the anonymous inner class, the compiler requires that the argument reference be final, like the argument to dest( ). If you forget, you’ll get a compile-time error message. ƒ An inner class can see • Outer surrounding class (it’s globala attributes) • final @ UU/IT

2008-01-30 | #23

Uppsala University

Scope class Bank { int i; void bills() { int k = 0; final f = 7; Bills s1 = new Bills() { // see i & f, not k public int get100() { return 0; } }; } } @ UU/IT

2008-01-30 | #24

8

Uppsala University

ActionListener (AL) // Not OOP class Foo implements ActionListener { Foo() { JButton b = new JButton(); b.addActionListener(this); // ugly! public void actionPerformed(ActionEvent e) { // doit } } } @ UU/IT

2008-01-30 | #25

Uppsala University

AL 2 // Sometimes ok, mostly not class Foo { class Bar implements ActionListener { public void actionPerformed(ActionEvent e) { // doit } } Foo() { JButton b = new JButton(); b.addActionListener(new Bar()); } } @ UU/IT

2008-01-30 | #26

Uppsala University

AL 2.1 class Foo { class Bar implements ActionListener { public void actionPerformed(ActionEvent e) { // doit } } Foo() { Bar bar = new Bar(); JButton b1 = new JButton(); JButton b2 = new JButton(); b1.addActionListener(bar); b2.addActionListener(bar); }

// smart, shares action

}

@ UU/IT

2008-01-30 | #27

9

Uppsala University

AL 3 // Good! class Foo { Foo() { JButton b = new JButton(); b.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // doit } }); } } @ UU/IT

2008-01-30 | #28

Uppsala University

AL 4 – scope? class Foo { private int i; Foo() { int k = 0; final m = 0; JButton b = new JButton(); b.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { // can see i and m, not k } }); } }

@ UU/IT

2008-01-30 | #29

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