Übungsblatt 11 - Lösungsvorschlag - Informatik

Universität Augsburg, Institut für Informatik
Prof. Dr. Werner Kießling
M. Endres, A. Huhn, T. Preisinger
Sommersemester 2006
20. Juli. 2006
Lösungsblatt 11
Informatik II
Aufgabe 1: Währungsrechner
CurrencyConverter.java
import
import
import
import
import
import
import
java.awt.*;
java.awt.event.*;
java.io.*;
java.net.*;
java.text.NumberFormat;
java.util.*;
javax.swing.*;
public class CurrencyConverter extends JFrame implements ActionListener {
final Currency EUR = new Currency("EUR", 1.0);
JComboBox cbCurrFrom, cbCurrTo;
JTextField tfAmountFrom = new JTextField(10);
JLabel lblAmountTo = new JLabel();
JButton btnConvert = new JButton("Umrechnen");
NumberFormat formatter = NumberFormat.getInstance();
public CurrencyConverter() {
super("Währungsrechner");
formatter.setMinimumFractionDigits(2);
formatter.setMaximumFractionDigits(2);
// Komponenenten erzeugen
Currency[] curr = getCurrencies();
cbCurrFrom = new JComboBox(curr);
cbCurrTo = new JComboBox(curr);
// ActionListener hinzufügen
btnConvert.addActionListener(this);
super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Oberfläche zusammenstellen
JComponent cp = (JComponent) getContentPane();
cp.setLayout(new GridBagLayout());
cp.add(tfAmountFrom, new GridBagConstraints(0, 0, 1, 1, 1.0, 0.0,
GridBagConstraints.FIRST_LINE_START, GridBagConstraints.HORIZONTAL,
new Insets(5, 5, 5, 5), 0, 0));
cp.add(cbCurrFrom, new GridBagConstraints(1, 0, 1, 1, 1.0, 0.0,
GridBagConstraints.FIRST_LINE_START, GridBagConstraints.HORIZONTAL,
new Insets(5, 0, 5, 5), 0, 0));
cp.add(new JLabel("in"), new GridBagConstraints(0, 1, 1, 1, 0.0, 0.0,
GridBagConstraints.LINE_END, GridBagConstraints.NONE,
new Insets(0, 5, 5, 5), 0, 0));
cp.add(cbCurrTo, new GridBagConstraints(1, 1, 1, 1, 1.0, 0.0,
GridBagConstraints.FIRST_LINE_START, GridBagConstraints.HORIZONTAL,
new Insets(0, 0, 5, 5), 0, 0));
cp.add(btnConvert, new GridBagConstraints(2, 1, 1, 1, 0.0, 0.0,
GridBagConstraints.FIRST_LINE_START, GridBagConstraints.NONE,
new Insets(0, 0, 5, 5), 0, 0));
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cp.add(new JLabel("Ergebnis:"), new GridBagConstraints(0, 2, 1, 1,
1.0, 0.0, GridBagConstraints.LINE_END, GridBagConstraints.NONE,
new Insets(0, 5, 5, 5), 0, 0));
cp.add(lblAmountTo, new GridBagConstraints(1, 2, 2, 1, 0.0, 0.0,
GridBagConstraints.FIRST_LINE_START, GridBagConstraints.NONE,
new Insets(0, 0, 5, 5), 0, 0));
pack();
}
public static void main(String[] args) {
new CurrencyConverter().setVisible(true);
}
public Currency[] getCurrencies() {
// Ohne Stream
Currency[] result = new Currency[] { EUR, new Currency("USD", 1.279),
new Currency("CHF", 1.5674), new Currency("GBP", 0.6933) };
// Mit Stream
Vector<Currency> curr = new Vector<Currency>();
curr.add(EUR);
try {
URL url = new URL(
"http://www.ecb.int/stats/eurofxref/eurofxref-daily.xml");
URLConnection con = url.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(
con.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
StringTokenizer tokens = new StringTokenizer(line, "’");
int count = tokens.countTokens();
// 1. Token: <Cube currency=
String first = tokens.nextToken();
if (first.endsWith("<Cube currency=") &&
count == 5) {
// 2. Token: Währungsname
String name = tokens.nextToken();
// 3. Token: rate=
tokens.nextElement();
// 4. Token: Umrechnungsfaktor
double factor = Double.parseDouble(tokens.nextToken());
curr.add(new Currency(name, factor));
}
}
in.close();
result = new Currency[curr.size()];
curr.copyInto(result);
} catch (IOException ioe) {;}
return result;
}
public void actionPerformed(ActionEvent e) {
double amount = 0;
try {
amount = Double.parseDouble(tfAmountFrom.getText().replace(’,’, ’.’));
// Umrechnung immer Quell-Währung zu Euro und dann
// Euro zu Zielwährung
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double toEUR = ((Currency) cbCurrFrom.getSelectedItem()).getToEUR();
double toResult = ((Currency) cbCurrTo.getSelectedItem()).getToEUR();
double result = amount / toEUR * toResult;
lblAmountTo.setText(formatter.format(result));
} catch (NumberFormatException nfe) {
JOptionPane.showMessageDialog(this, "Keine Zahl!", "Fehler",
JOptionPane.ERROR_MESSAGE);
}
}
class Currency {
// Währungs-Kürzel
final String name;
// Umrechnung zu 1,00 EUR
double rateEUR;
public Currency(String name, double rateEUR) {
this.name = name;
this.rateEUR = rateEUR;
}
public String getName() { return name; }
public double getToEUR() { return rateEUR; }
public String toString() { return name; }
}
}
Aufgabe 2: Datei-Explorer
FileExplorer.java
import
import
import
import
import
import
import
java.awt.*;
java.io.File;
java.util.*;
javax.swing.*;
javax.swing.border.EmptyBorder;
javax.swing.event.*;
javax.swing.tree.*;
public class FileExplorer extends JFrame {
JTree tree;
JTextArea
JCheckBox
JCheckBox
JCheckBox
JCheckBox
JCheckBox
list = new JTextArea();
chFile = new JCheckBox("Datei");
chDir = new JCheckBox("Verzeichnis");
chHidden = new JCheckBox("versteckt");
chReadable = new JCheckBox("lesbar");
chReadOnly = new JCheckBox("schreibgeschützt");
public FileExplorer(File file) {
super("File Explorer");
setDefaultCloseOperation(EXIT_ON_CLOSE);
tree = new JTree(new DirectoryTreeNode(file));
//tree = new JTree(new DirectoryTreeNode(new File("C:\\")));
tree.addTreeSelectionListener(new TreeSelectionListener() {
public void valueChanged(TreeSelectionEvent e) {
TreePath path = tree.getSelectionPath();
DirectoryTreeNode selection =
(DirectoryTreeNode) path.getLastPathComponent();
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if (selection.isLeaf()) list.setText("");
else {
// Verzeichnis: enthaltene Dateien in der Liste anzeigen
StringBuffer sb = new StringBuffer();
Enumeration<DirectoryTreeNode> elements = selection.children();
while (elements.hasMoreElements()) {
sb.append(elements.nextElement().toString());
sb.append(’\n’);
}
list.setText(sb.toString());
}
// CheckBoxen markieren
File curFile = selection.getFile();
chHidden.setSelected(curFile.isHidden());
chFile.setSelected(curFile.isFile());
chDir.setSelected(curFile.isDirectory());
chReadOnly.setSelected(curFile.canWrite());
chReadable.setSelected(curFile.canRead());
}
});
ButtonGroup bg = new ButtonGroup();
bg.add(chFile);
bg.add(chDir);
chHidden.setEnabled(false);
chReadable.setEnabled(false);
chReadOnly.setEnabled(false);
chFile.setEnabled(false);
chDir.setEnabled(false);
list.setEditable(false);
JComponent cp = (JComponent) getContentPane();
cp.setBorder(new EmptyBorder(5,5,5,5));
cp.add(new JScrollPane(tree), BorderLayout.LINE_START);
JPanel pnlRight = new JPanel(new BorderLayout());
JPanel pnlAttributes = new JPanel();
pnlAttributes.setLayout(new GridLayout(0, 1));
pnlAttributes.add(chHidden);
pnlAttributes.add(chReadable);
pnlAttributes.add(chReadOnly);
pnlAttributes.add(new JLabel(" Typ: "));
pnlAttributes.add(chFile);
pnlAttributes.add(chDir);
pnlAttributes.add(new JLabel(" Inhalt: "));
pnlRight.add(pnlAttributes, BorderLayout.PAGE_START);
pnlRight.add(new JScrollPane(list), BorderLayout.CENTER);
cp.setLayout(new BorderLayout());
cp.add(new JScrollPane(tree), BorderLayout.LINE_START);
cp.add(pnlRight, BorderLayout.CENTER);
pack();
}
public static void main(String[] args) {
new FileExplorer(new File(".")).setVisible(true);
}
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class DirectoryTreeNode implements TreeNode {
File file;
public DirectoryTreeNode(File file) { this.file = file; }
public File getFile() { return file; }
// Enthaltene Datei an bestimmter Stelle zurückgeben
public DirectoryTreeNode getChildAt(int childIndex) {
return new DirectoryTreeNode(file.listFiles()[childIndex]);
}
// Anzahl enthaltener Dateien
public int getChildCount() {
File[] children = file.listFiles();
return children != null ? children.length : 0;
}
// Übergeordnetes Verzeichnis zurückliefern
public DirectoryTreeNode getParent() {
return new DirectoryTreeNode(file.getParentFile());
}
public int getIndex(TreeNode node) {
// Knoten suchen
if (!(node instanceof DirectoryTreeNode)) {
// falscher Typ des Knotens
return -1;
}
File obj = ((DirectoryTreeNode) node).getFile();
for (int i = 0; i < file.listFiles().length; i++) {
if (file.equals(obj)) return i;
}
return -1;
}
// Verzeichnisse können "Kinder" haben
public boolean getAllowsChildren() { return file.isDirectory(); }
// Eine einfache Datei ist ein Blatt
public boolean isLeaf() { return file.isFile(); }
public Enumeration<DirectoryTreeNode> children() {
Vector<DirectoryTreeNode> dir = new Vector<DirectoryTreeNode>();
for (File elem : file.listFiles()) {
dir.add(new DirectoryTreeNode(elem));
}
return dir.elements();
}
public String toString() { return file.getName(); }
}
}
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