第20 章 ： JavaIO编程案例
91 数字大小比较
输入3个整数，并求出3个整数最大值和最小值
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
class InputUtil {
/**
* 读取指定个数的整数输入
*
* @param num 指定要输入的整数个数
* @return 所有读取的整数数组
* @throws IOException
*/
public static int[] getIntList(int num) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
System.out.println("请输入" + num + "个整数：");
int[] list = new int[num];
int count = 0;
while (count max) {
max = x;
}
if (min > x) {
min = x;
}
}
return new int[]{max, min};
}
}
class Demo {
public static void main(String[] args) throws IOException {
// 读取3个数据
int[] list = InputUtil.getIntList(3);
int[] data = NumberUtil.getMaxMin(list);
System.out.println("最大值：" + data[0]);
System.out.println("最小值：" + data[1]);
}
}
从键盘输入文件名和文件内容，然后将文件内容保存到文件中 1、定义接口 2、工具类 3、实现接口类 4、工厂类 5、测试函数
import java.io.*;
class InputUtil {
private static final BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
public static String getInput(String prompt) {
System.out.println(prompt);
String msg = null;
while (true) {
try {
msg = reader.readLine();
if (!"".equals(msg)) {
break;
} else {
System.out.println("请输入非空字符串：");
}
} catch (IOException e) {
}
}
return msg;
}
}
interface IFileService {
public static final String FILE_DIR = "demo";
public boolean save();
}
class FileServiceImpl implements IFileService {
private String filename;
private String content;
public FileServiceImpl() {
this.filename = InputUtil.getInput("请输入文件名");
this.content = InputUtil.getInput("请输入文件内容");
}
@Override
public boolean save() {
String fullname = this.FILE_DIR + File.separator + this.filename;
PrintWriter writer = null;
try {
writer = new PrintWriter(fullname);
writer.print(this.content);
} catch (FileNotFoundException e) {
e.printStackTrace();
} finally {
if (writer != null) {
writer.close();
}
}
return false;
}
}
class Factory{
private Factory(){}
public static FileServiceImpl getInstance(){
return new FileServiceImpl();
}
}
class Demo {
// 项目启动时创建文件夹
static {
File file = new File(IFileService.FILE_DIR);
if (!file.exists()) {
file.mkdirs();
}
}
public static void main(String[] args) throws IOException {
FileServiceImpl fileService = Factory.getInstance();
fileService.save();
}
}
键盘传入多个字符串到程序中，并将它们按照逆序输出到屏幕
设计考虑： 1、字符串内容随时修改，使用StringBuffer 2、由用户自己决定是否继续输入
实现步骤 1、定义接口 操作标准 2、定义实现类 3、定义工厂类 4、编写辅助类 5、编写测试类
实现代码 IStringService.java
public interface IStringService {
public void append(String str);
public String[] reverse();
}
StringServiceImpl.java
public class StringServiceImpl implements IStringService{
private StringBuffer data = new StringBuffer();
public void append(String str){
this.data.append(str).append("|");
}
public String[] reverse(){
String[] list = this.data.toString().split("\\|");
String[] tmp = new String[list.length];
for(int i=0; i';
}
@Override
public int compareTo(Student obj) {
return Double.compare(obj.score, this.score);
}
}
StudentServiceImpl.java
import java.util.Arrays;
public class StudentServiceImpl implements IStudentService {
private String content;
private Student[] students;
public StudentServiceImpl(String content) {
this.content = content;
this.handle();
}
private void handle(){
String[] list = this.content.split("\\|");
this.students = new Student[list.length];
for(int i=0; i= 3;
}
/**
* 实现核心逻辑
*/
@Override
public boolean login(String name, String password) {
this.tryCount ++;
if("root".equals(name) && "123456".equals(password)){
return true;
} else{
return false;
}
}
}
UserServiceProxy.java
import util.InputUtil;
public class UserServiceProxy implements IUserService {
private IUserService userService;
public UserServiceProxy(IUserService userService) {
this.userService = userService;
}
@Override
public boolean isExit() {
return this.userService.isExit();
}
/**
* 实现辅助逻辑
*/
@Override
public boolean login(String name, String password) {
while (!this.isExit()) {
String inputName = InputUtil.getString("请输入用户名：");
String inputPassword = InputUtil.getString("请输入密码：");
if (this.userService.login(inputName, inputPassword)) {
System.out.println("登录成功");
System.exit(0);
} else {
System.out.println("用户名或密码错误，请重试");
}
}
System.out.println("重试次数过多，请稍后重试");
return true;
}
}
Factory.java
import util.InputUtil;
public class Factory {
private Factory(){}
public static IUserService getInstance(){
return new UserServiceProxy(new UserServiceImpl());
}
}
Demo.java
public class Demo {
public static void main(String[] args) {
Factory.getInstance().login(null, null);
}
}
1、输入候选人名单 2、统计每个候选人票数 3、显示最终投票结果 思路分析
1、定义数据结构：
Student
name
sid
vote
2、操作接口类
IVoteService
void inc(int sid)
Student[] result() 排序数据
Student[] getData() 未排序数据
3、实现类
VoteServiceImpl
4、工厂类
Factory
5、测试类
Demo
实现代码
数据结构 Student.java
public class Student implements Comparable {
private String name;
private int sid;
private int vote;
public Student(String name, int sid, int vote) {
this.name = name;
this.sid = sid;
this.vote = vote;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
public int getVote() {
return vote;
}
public void setVote(int vote) {
this.vote = vote;
}
@Override
public int compareTo(Student obj) {
return obj.vote - this.vote;
}
@Override
public String toString() {
return String.format("[%s] %s - %s", sid, name, vote);
}
}
接口 IVoteService.java
public interface IVoteService {
public void inc(int sid);
public Student result();
public Student[] getData();
}
实现类 VoteServiceImpl.java
import util.InputUtil;
import java.util.Arrays;
public class VoteServiceImpl implements IVoteService {
private Student[] students;
public VoteServiceImpl() {
this.students = new Student[]{
new Student("张三", 1, 0),
new Student("李四", 2, 0),
new Student("王五", 3, 0),
};
}
@Override
public void inc(int sid) {
for(Student s : this.students){
if(s.getSid() == sid){
s.setVote(s.getVote() + 1);
}
}
}
@Override
public Student result() {
Arrays.sort(this.students);
return this.students[0];
}
@Override
public Student[] getData() {
return this.students;
}
}
工产类 Factory.java
public class Factory {
private Factory(){}
public static IVoteService getInstance(){
return new VoteServiceImpl();
}
}
菜单类 Menu.java
import util.InputUtil;
import java.util.Arrays;
public class Menu {
private IVoteService voteService;
public Menu() {
this.voteService = Factory.getInstance();
this.choose();
}
public void choose(){
this.help();
String num = InputUtil.getString("请选择：");
switch (num){
case "1":
String sid = InputUtil.getString("请输入候选人id");
this.voteService.inc(Integer.parseInt(sid));
this.choose();
break;
case "2":
System.out.println(Arrays.toString(this.voteService.getData()));
this.choose();
break;
case "3":
System.out.println(this.voteService.result());
this.choose();
break;
case "0":
System.out.println("拜拜...");
System.exit(0);
default:
help();
this.choose();
}
}
public void help(){
System.out.println("【1】候选人增加票数");
System.out.println("【2】显示投票统计");
System.out.println("【3】显示统计结果");
System.out.println("【0】退出系统");
}
}
测试类 Demo.java
public class Demo {
public static void main(String[] args) {
new Menu();
}
}
