Java学习路线-28：JavaIO编程案例
【摘要】 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 *...
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 < num) { String msg = reader.readLine(); if (msg.matches("\\d+")) { list[count++] = Integer.parseInt(msg); } else { System.out.println("请输入整数"); } } reader.close(); return list; }
}
class NumberUtil { /** * 获取int 型数组中最大值和最小值 * * @param list 整数数组 * @return int[] {max, min} */ public static int[] getMaxMin(int[] list) { int max = list[0]; int min = list[0]; for (int x : list) { if (x > 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]); }
}
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92 文件保存
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(); }
}
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93 字符串逆序显示
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();
}
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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<list.length; i++){ tmp[i] = list[list.length - i - 1]; } return tmp; }
}
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InputUtil.java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
class InputUtil { private static final BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); public static String getString(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; } public static void main(String[] args) { System.out.println(InputUtil.getString("请输入")); }
}
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Factory.java
class Factory{ private Factory(){} public static StringServiceImpl getInstance(){ return new StringServiceImpl(); }
}
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Menu.java
import java.util.Arrays;
public class Menu { private StringServiceImpl stringServiceImpl; public Menu() { this.stringServiceImpl = Factory.getInstance(); this.choose(); } public void choose() { help(); String msg = InputUtil.getString("请选择："); switch (msg) { case "1": this.stringServiceImpl.append(InputUtil.getString("请输入字符串：")); choose(); case "2": System.out.println(Arrays.toString(this.stringServiceImpl.reverse())); choose(); case "0": System.exit(0); default: choose(); } } public static void help() { System.out.println("[1]输入内容："); System.out.println("[2]输出反转内容："); System.out.println("[0]退出"); }
}
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Demo.java
class Demo{ public static void main(String[] args) { new Menu(); }
}
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94 数据排序处理
键盘输入数据 姓名:成绩|姓名:成绩
eg:
Tom:89|Jack:91|Tony:86
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按照成绩由高到低排序
思路：
Comparable + Arrays
代码实现
IStudentService.java
public interface IStudentService { Student[] getData();
}
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Student.java
public class Student implements Comparable<Student>{ private String name; private double score; public Student(String name, double score) { this.name = name; this.score = score; } @Override public String toString() { return "Student<" + name + ", " + score + '>'; } @Override public int compareTo(Student obj) { return Double.compare(obj.score, this.score); }
}
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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<list.length; i++){ String[] items = list[i].split(":"); this.students[i] = new Student(items[0], Double.parseDouble(items[1])); } } @Override public Student[] getData() { Arrays.sort(this.students); return this.students; }
}
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Factory.java
public class Factory { private Factory(){} public static StudentServiceImpl getInstance(){ return new StudentServiceImpl(InputUtil.getString("请输入数据：")); }
}
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Demo.java
import java.util.Arrays;
public class Demo { public static void main(String[] args) { // Tom:89|Jack:91|Tony:86 System.out.println(Arrays.toString(Factory.getInstance().getData())); // [Student<Jack, 91.0>, Student<Tom, 89.0>, Student<Tony, 86.0>] }
}
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95 数据排序处理深入
扩展上一节内容，将输入信息保存到文件中，还可以添加信息，并且查看全部数据
确认保存位置
格式统一
FileUtil.java文件读取工具类
package util;
import java.io.*;
import java.util.Scanner;
public class FileUtil { public static String read(File file) throws FileNotFoundException { Scanner scanner = new Scanner(file); StringBuilder contents = new StringBuilder(); while (scanner.hasNext()) { contents.append(scanner.next()); } scanner.close(); return contents.toString(); } public static void append(File file, String content) throws IOException { PrintWriter writer = new PrintWriter(new FileWriter(file, true)); writer.write(content); writer.close(); } public static void save(File file, String content) throws IOException { PrintWriter writer = new PrintWriter(file); writer.write(content); writer.close(); } public static void main(String[] args) throws IOException { File file = new File("demo.txt"); FileUtil.save(file, "你好"); FileUtil.append(file, "你也好"); System.out.println(FileUtil.read(file)); }
}
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96 奇偶数统计
输入字符串拆分后统计奇数，偶数个数
接口INumberService.java
public interface INumberService { public int[] handle();
}
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实现类 NumberServiceImpl.java
import util.InputUtil;
public class NumberServiceImpl implements INumberService{ private String str; public NumberServiceImpl(){ this.str = InputUtil.getString("请输入数字串："); } @Override public int[] handle() { String[] numbers = this.str.split(""); // 偶数， 奇数 int[] result = new int[]{0, 0}; for(String num : numbers){ if(Integer.parseInt(num) % 2 == 0){ result[0] ++; } else{ result[1] ++; } } return result; }
}
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测试类 Demo.java
import java.util.Arrays;
public class Demo { public static void main(String[] args) { System.out.println(Arrays.toString(new NumberServiceImpl().handle())); // 1234567890 // [5, 5] }
}
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97 用户登录
输入用户名和密码 root 123456
如果没有输入则提示输入
输入错误3次退出
提示登录成功
真实业务只实现核心功能，辅助逻辑处理交给代理控制
接口类
IUserService
isExit
login
实现类
UserServiceImpl
代理类
UserServiceProxy
工厂类
Factory
测试类
Demo
实现代码
IUserService.java
public interface IUserService { public boolean isExit(); public boolean login(String name, String password);
}
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UserServiceImpl.java
public class UserServiceImpl implements IUserService{ private int tryCount = 0; @Override public boolean isExit() { // 超过三次错误 return this.tryCount >= 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; } }
}
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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; }
}
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Factory.java
import util.InputUtil;
public class Factory { private Factory(){} public static IUserService getInstance(){ return new UserServiceProxy(new UserServiceImpl()); }
}
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Demo.java
public class Demo { public static void main(String[] args) { Factory.getInstance().login(null, null); }
}
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98 投票选举
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
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实现代码
数据结构 Student.java
public class Student implements Comparable<Student> { 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); }
}
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接口 IVoteService.java
public interface IVoteService { public void inc(int sid); public Student result(); public Student[] getData();
}
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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; }
}
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工产类 Factory.java
public class Factory { private Factory(){} public static IVoteService getInstance(){ return new VoteServiceImpl(); }
}
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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"); }
}
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测试类 Demo.java
public class Demo { public static void main(String[] args) { new Menu(); }
}
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文章来源: pengshiyu.blog.csdn.net，作者：彭世瑜，版权归原作者所有，如需转载，请联系作者。
原文链接：pengshiyu.blog.csdn.net/article/details/103649318
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