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《Java语言程序设计（基础篇）》（第10版 梁勇 著）

第十七章 练习题答案

17.1

import java.io.*; import java.util.*;

public class Exercise17_01 {

public static void main(String[] args) throws IOException { try (

Formatter output =

new Formatter(new FileOutputStream(\, true)); ) {

for (int i = 0; i < 100; i++)

output.format(\, (int)(Math.random() * 100000)); } } }

17.2

import java.io.*;

public class Exercise17_02 {

public static void main(String[] args) throws IOException { try (

DataOutputStream output =

new DataOutputStream(new FileOutputStream(\, true)); ) {

for (int i = 0; i < 100; i++)

output.writeInt((int)(Math.random() * 100000)); }

System.out.println(\); } }

17.3

import java.io.*;

public class Exercise17_03 { /** Main method */

public static void main(String[] args) { // Read data int count = 0;

try ( // Declare and create data input and output streams DataInputStream dis =

new DataInputStream(new FileInputStream(\)); ) {

int total = 0;

while (dis.available() > 0) { int temp = dis.readInt(); total += temp; count++;

System.out.print(temp + \); }

System.out.println(\ + count); System.out.println(\ + total); }

catch (FileNotFoundException ex) { System.out.println(\); }

catch (IOException ex) {

System.out.println(ex.getMessage()); } } }

17.4

import java.io.*;

public class Exercise17_04 {

public static void main(String[] args) throws IOException { try (

BufferedReader input = new BufferedReader(new FileReader(args[0])); DataOutputStream output = new DataOutputStream(new FileOutputStream(args[1])); ) {

String line;

while ((line = input.readLine()) != null) output.writeUTF(line); }

try (

InputStream input1 = new FileInputStream(args[0]); InputStream input2 = new FileInputStream(args[1]); ) {

System.out.println(args[0] + \ + input1.available() + \bytes\);

System.out.println(args[1] + \ + input2.available() + \bytes\); } } }

17.5

import java.io.*;

public class Exercise17_05 {

public static void main(String[] args) throws IOException { try (

ObjectOutputStream output = new ObjectOutputStream( new FileOutputStream(\)); ) {

output.writeObject(new int[]{1, 2, 3, 4, 5}); output.writeObject(new java.util.Date()); output.writeDouble(5.5); } } }

17.6

import java.io.*;

public class Exercise17_06 {

public static void main(String[] args) throws IOException { try (

ObjectOutputStream output = new ObjectOutputStream( new FileOutputStream(\)); ) {

output.writeObject(new Loan(2.5, 5, 1000)); output.writeObject(new Loan(3.5, 5, 2000)); output.writeObject(new Loan(4.5, 5, 3000)); output.writeObject(new Loan(5.5, 5, 4000));

output.writeObject(new Loan(6.5, 5, 5000)); } } }

17.7

import java.io.*;

public class Exercise17_07 {

public static void main(String[] args) { int total = 0; int count = 0;

try (

ObjectInputStream input = new ObjectInputStream(new BufferedInputStream( new FileInputStream(\))); ) {

while (true) {

Loan loan = (Loan)(input.readObject()); total += loan.getLoanAmount(); count++; } }

catch (EOFException ex) {

System.out.println(\ + count); System.out.println(\ + total); }

catch (Exception ex) { ex.printStackTrace(); } } }

17.8

import java.io.*;

public class Exercise17_08 {

public static void main(String[] args) throws IOException { try (

RandomAccessFile raf = new RandomAccessFile(\, \); ) {

int count = 0;

if (raf.length() > 0) count = raf.readInt();

raf.seek(0);

raf.writeInt(++count);

System.out.println(\ + count); } } }

17.9

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();