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import java.io.*;

import javafx.application.Application;

import javafx.geometry.Pos;

import javafx.scene.Scene;

import javafx.scene.control.Button;

import javafx.scene.control.Label;

import javafx.scene.control.TextField;

import javafx.scene.layout.BorderPane;

import javafx.scene.layout.GridPane;

import javafx.scene.layout.HBox;

import javafx.stage.Stage;

public class Exercise17_09 extends Application {

// Specify the size of five string fields in the record

final static int NAME_SIZE = 32;

final static int STREET_SIZE = 32;

final static int CITY_SIZE = 20;

final static int STATE_SIZE = 2;

final static int ZIP_SIZE = 5;

final static int RECORD_SIZE =

(NAME_SIZE + STREET_SIZE + CITY_SIZE + STATE_SIZE + ZIP_SIZE);

// Access address.dat using RandomAccessFile

private RandomAccessFile raf;

// Text fields

private TextField tfName = new TextField();

private TextField tfStreet = new TextField();

private TextField tfCity = new TextField();

private TextField tfState = new TextField();

private TextField tfZip = new TextField();

// Buttons

private Button btAdd = new Button("Add");

private Button btFirst = new Button("First");

private Button btNext = new Button("Next");

private Button btPrevious = new Button("Previous");

private Button btLast = new Button("Last");

private Button btUpdate = new Button("Update");

public Exercise17_09() {

// Open or create a random access file

try {

raf = new RandomAccessFile("address.dat", "rw");

}

catch(IOException ex) {

ex.printStackTrace();

System.exit(1);

}

}

@Override

public void start(Stage primaryStage) {

tfState.setPrefColumnCount(2);

tfZip.setPrefColumnCount(4);

tfCity.setPrefColumnCount(12);

// Pane p1 for holding labels java基础篇17章 Name, Street, and City

GridPane p1 = new GridPane();

p1.setAlignment(Pos.CENTER);

p1.setHgap(5);

p1.setVgap(5);

p1.add(new Label("Name"), 0, 0);

p1.add(new Label("Street"), 0, 1);

p1.add(new Label("City"), 0, 2);

p1.add(tfName, 1, 0);

p1.add(tfStreet, 1, 1);

HBox p2 = new HBox(5);

p2.getChildren().addAll(tfCity, new Label("State"), tfState,

new Label("Zip"), tfZip);

p1.add(p2, 1, 2);

// Add buttons to a pane

HBox p3 = new HBox(5);

p3.getChildren().addAll(btAdd, btFirst, btNext, btPrevious,

btLast, btUpdate);

p3.setAlignment(Pos.CENTER);

// Add p1 and p3 to a border pane

BorderPane borderPane = new BorderPane();

borderPane.setCenter(p1);

borderPane.setBottom(p3);

// Create a scene and place it in the stage

Scene scene = new Scene(borderPane, 400, 120);

primaryStage.setTitle("Exercise17_09"); // Set the stage title

primaryStage.setScene(scene); // Place the scene in the stage

primaryStage.show(); // Display the stage

// Display the first record if exists

try {

if (raf.length() > 0) readAddress(0);

}

catch (IOException ex) {

ex.printStackTrace();

}

btAdd.setOnAction(e -> {

try {

writeAddress(raf.length());

}

catch (Exception ex) {

}

});

btFirst.setOnAction(e -> {

try {

if (raf.length() > 0) readAddress(0);

}

catch (IOException ex) {

}

});

btNext.setOnAction(e -> {

try {

long currentPosition = raf.getFilePointer();

if (currentPosition < raf.length())

readAddress(currentPosition);

}

catch (IOException ex) {

}

});

btPrevious.setOnAction(e -> {

try {

long currentPosition = raf.getFilePointer();

if (currentPosition - 2 * RECORD_SIZE > 0)

// Why 2 * 2 * RECORD_SIZE? See the follow-up remarks

readAddress(currentPosition - 2 * 2 * RECORD_SIZE);

else

readAddress(0);

}

catch (IOException ex) {

}

});

btLast.setOnAction(e -> {

try {

long lastPosition = raf.length();

if (lastPosition > 0)

// Why 2 * RECORD_SIZE? See the follow-up remarks

readAddress(lastPosition - 2 * RECORD_SIZE);

}

catch (IOException ex) {

}

});

btUpdate.setOnAction(e -> {

try {

writeAddress(raf.getFilePointer() - 2 * RECORD_SIZE);

}

catch (IOException ex) {

}

});

}

/ Write a record at the end of the file */

public void writeAddress(long position) {

try {

raf.seek(position);

FixedLengthStringIO.writeFixedLengthString(

tfName.getText(), NAME_SIZE, raf);

FixedLengthStringIO.writeFixedLengthString(

tfStreet.getText(), STREET_SIZE, raf);

FixedLengthStringIO.writeFixedLengthString(

tfCity.getText(), CITY_SIZE, raf);

FixedLengthStringIO.writeFixedLengthString(

tfState.getText(), STATE_SIZE, raf);

FixedLengthStringIO.writeFixedLengthString(

tfZip.getText(), ZIP_SIZE, raf);

}

catch (IOException ex) {

ex.printStackTrace();

}

}

/ Read a record at the specified position */

public void readAddress(long position) throws IOException {

raf.seek(position);

String name = FixedLengthStringIO.readFixedLengthString(

NAME_SIZE, raf);

String street = FixedLengthStringIO.readFixedLengthString(

STREET_SIZE, raf);

String city = FixedLengthStringIO.readFixedLengthString(

CITY_SIZE, raf);

String state = FixedLengthStringIO.readFixedLengthString(

STATE_SIZE, raf);

String zip = FixedLengthStringIO.readFixedLengthString(

ZIP_SIZE, raf);

tfName.setText(name);

tfStreet.setText(street);

tfCity.setText(city);

tfState.setText(state);

tfZip.setText(zip);

}

/

* The main method is only needed for the IDE with limited

* JavaFX support. Not needed for running from the command line.

*/

public static void main(String[] args) {

launch(args);

}

}

class FixedLengthStringIO {

/ Read fixed number of characters from a DataInput stream */

public static String readFixedLengthString(int size,

DataInput in) throws IOException {

// Declare an array of characters

char[] chars = new char[size];

// Read fixed number of characters to the array

for (int i = 0; i < size; i++)

chars[i] = in.readChar();

return new String(chars);

}

/ Write fixed number of characters to a DataOutput stream */

public static void writeFixedLengthString(String s, int size,

DataOutput out) throws IOException {

char[] chars = new char[size];

// Fill in string with characters

s.getChars(0, s.length(), chars, 0);

// Fill in blank characters in the rest of the array

for (int i = Math.min(s.length(), size); i < chars.length; i++)

chars[i] = ' ';

// Create and write a new string padded with blank characters

out.writeChars(new String(chars));

}