《Java语言程序设计(基础篇)》(第10版 梁勇 著)第十一章练习题答案

String[] students = course1.getStudents();

for (int i = 0; i < course1.getNumberOfStudents(); i++) System.out.print(students[i] + \);

System.out.println();

System.out.print(\ + course2.getNumberOfStudents()); } }

class Course {

private String name;

private java.util.ArrayList students = new java.util.ArrayList<>();

public Course(String name) { this.name = name; }

public void addStudent(String student) { students.add(student); }

public String[] getStudents() {

// String[] temp = new String[students.size()]; // for (int i = 0; i < temp.length; i++) // temp[i] = (String) students.get(i); //

// return temp;

// Or better to use

String[] result = new String[students.size()]; students.toArray(result); return result; }

public int getNumberOfStudents() { return students.size(); } }

11.6

import java.util.*;

public class Exercise11_06 {

public static void main(String[] args) { ArrayList list = new ArrayList(); list.add(new Loan()); list.add(new Date());

for (int i = 0; i < list.size(); i++) System.out.println(list.get(i)); } }

11.7

import java.util.ArrayList;

public class Exercise11_07 {

public static void main(String[] args) { ArrayList list = new ArrayList<>(); for (int i = 0; i < 10; i++) { list.add(i); }

shuffle(list);

for (int i = 0; i < list.size(); i++) { System.out.print(list.get(i) + \); } }

public static void shuffle(ArrayList list) { for (int i = 0; i < list.size(); i++) { int index = (int)(Math.random() * 10); int temp = list.get(index); list.set(index, list.get(i)); list.set(i, temp); } } }

11.8

public class Exercise11_08 {

public static void main (String[] args) {

Account1.setAnnualInterestRate(5.5);

Account1 account = new Account1(\, 1122, 1000); account.deposit(30); account.deposit(40); account.deposit(50);

account.withdraw(5); account.withdraw(4); account.withdraw(2);

System.out.println(\ + account.getName()); System.out.println(\ + Account1.getAnnualInterestRate());

System.out.println(\ + account.getBalance());

java.util.ArrayList list = account.getTransactions();

System.out.printf(\, \, \, \, \);

for (int i = 0; i < list.size(); i++) {

Transaction transaction = (Transaction)(list.get(i));

System.out.printf(\, transaction.getDate(), transaction.getType(), transaction.getAmount(), transaction.getBalance()); } } }

class Account1 { private int id; private String name; private double balance;

private static double annualInterestRate; private java.util.Date dateCreated;

private java.util.ArrayList transactions = new java.util.ArrayList();

public Account1() {

dateCreated = new java.util.Date(); }

public Account1(String name, int id, double balance) { this.id = id;

this.name = name; this.balance = balance;

dateCreated = new java.util.Date(); }

public int getId() { return this.id; }

public double getBalance() { return balance; }

public java.util.ArrayList getTransactions() { return transactions; }

public String getName() { return name; }

public static double getAnnualInterestRate() { return annualInterestRate; }

public void setId(int id) { this.id =id; }

public void setBalance(double balance) { this.balance = balance; }

public static void setAnnualInterestRate(double annualInterestRate) { Account1.annualInterestRate = annualInterestRate; }

public double getMonthlyInterest() {

return balance * (annualInterestRate / 1200); }

public java.util.Date getDateCreated() { return dateCreated; }

public void withdraw(double amount) { balance -= amount;

transactions.add(new Transaction('W', amount, balance, \)); }

public void deposit(double amount) { balance += amount;

transactions.add(new Transaction('D', amount, balance, \)); } }

class Transaction {

private java.util.Date date; private char type; private double amount; private double balance; private String description;

public Transaction(char type, double amount, double balance, String description) { date = new java.util.Date(); this.type = type; this.amount = amount; this.balance = balance;

this.description = description; }

public java.util.Date getDate() { return date; }

public char getType() { return type; }

public double getAmount() { return amount; }

public double getBalance() { return balance; }