Java 的 IO流： 使用BufferedWriter ， BufferedReader 和 .txt文件， 简单模拟电话本 。

任务需求2：

                     电话本信息包括：姓名、性别、电话号码，将电话本信息写到文件中，并能够进行操作：

                                      1） 将信息全部读到内存中，在内存中进行增删改操作，然后再重写文件；

                                      2）电话本信息写到文件时，每个属性间添加符号，使用split分割
                     所需知识点：

                                       1.运用File类进行文件和目录操作；

                                       2.用字节流、字符流实现文件的读写；

代码如下： 

package cn.demo.main;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class Main {

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

		JavaDemo();
	}

	private static void JavaDemo() throws IOException, FileNotFoundException {
		File file = new File("D:\\homework\\phone.txt");
		FileWriter fw = new FileWriter(file);
		BufferedWriter bw = new BufferedWriter(fw);
		int newFlag = 0 ;
		while(newFlag==0){
		newFlag = MainDemo(file, bw, newFlag);
		}
	}

	private static int MainDemo(File file, BufferedWriter bw, int newFlag)
			throws IOException, FileNotFoundException {
		Demo();
		Scanner scr = new Scanner(System.in);
		int number = scr.nextInt() ; 
		if(number==1){
			Demo1(scr, bw);
		}else if(number==2){
			Demo2(file, scr);
		}else if(number==3){
			Demo3(file, scr);
		}else if(number==4){
			Demo4(file, scr);
		}else{
			newFlag = 1 ;
			System.out.println("退出！");
		}
		return newFlag;
	}

	private static void Demo4(File file, Scanner scr)
			throws FileNotFoundException, IOException {
		System.out.println("--查询界面--");
		System.out.println("全部信息如下：");
		BufferedReader br = new BufferedReader(new FileReader(file));
		String line = br.readLine() ;
		StringBuffer sbr = new StringBuffer() ;
		while(line!=null){
			sbr.append(line);
			line = br.readLine() ;
			if(line!=null){
				sbr.append("+");
			}
		}
		String[] arr = sbr.toString().split("\\+");
		for(int i=0;i<arr.length;i++){
			System.out.println(arr[i]);
		}
		System.out.println("输入所要查询的名字：");
		String namePeople = scr.next() ;
		int flag = 0 ; 
		for(int i=0;i<arr.length;i++){
			String[] arr1 = arr[i].split(",");
			if(namePeople.equals(arr1[0])){
				System.out.println("姓名："+arr1[0]);
				System.out.println("性别："+arr1[1]);
				System.out.println("电话："+arr1[2]);
				flag = 1 ;
			}
		}
		if(flag==0){
			System.out.println("没有此人信息！");
		}
	}

	private static void Demo3(File file, Scanner scr)
			throws FileNotFoundException, IOException {
		System.out.println("--修改界面--");
		System.out.println("输入需要修改的姓名：");
		String name = scr.next();
		System.out.println("输入需要修改的年龄：");
		String age = scr.next() ;
		System.out.println("输入需要修改的电话号码：");
		String tele = scr.next() ; 
		String str = name + "," + age + "," + tele ;
		BufferedReader br = new BufferedReader(new FileReader(file));
		String line = br.readLine() ;
		StringBuffer sbr = new StringBuffer() ;
		while(line!=null){
			sbr.append(line);
			line = br.readLine() ;
			if(line!=null){
				sbr.append("+");
			}
		}
		int flag = 0 ;
		String[] arr = sbr.toString().split("\\+");
		File file1 = new File("D:\\homework\\phone.txt");
		FileWriter fw1 = new FileWriter(file1);
		BufferedWriter bw1 = new BufferedWriter(fw1);
		for(int i=0;i<arr.length;i++){
			if(arr[i].equals(str)){
			System.out.println("请输入修改的信息：");
			System.out.println("新姓名：");
			String newName = scr.next();
			System.out.println("新年龄：");
			String newAge = scr.next() ;
			System.out.println("新电话号码：");
			String newTele = scr.next() ;
			String newPeople = 	newName + "," + newAge + "," + newTele ;
			bw1.write(newPeople);
			bw1.newLine();
			bw1.flush();
			flag = 1; 
			}else{
				bw1.write(arr[i]);
				bw1.newLine();
				bw1.flush();
			}
		}
		if(flag==0){
			System.out.println("没有此人信息！");
		}
	}

	private static void Demo2(File file, Scanner scr)
			throws FileNotFoundException, IOException {
		System.out.println("--删除界面--");
		System.out.println("输入删除的姓名：");
		String name = scr.next();
		System.out.println("输入删除的年龄：");
		String age = scr.next() ;
		System.out.println("输入删除的电话号码：");
		String tele = scr.next() ; 
		String str = name + "," + age + "," + tele ;
		BufferedReader br = new BufferedReader(new FileReader(file));
		String line = br.readLine() ;
		StringBuffer sbr = new StringBuffer() ;
		while(line!=null){
			sbr.append(line);
			line = br.readLine() ;
			if(line!=null){
				sbr.append("+");
			}
		}
		int flag = 0 ;
		String[] arr = sbr.toString().split("\\+");
		File file1 = new File("D:\\homework\\phone.txt");
		FileWriter fw1 = new FileWriter(file1);
		BufferedWriter bw1 = new BufferedWriter(fw1);
		for(int i=0;i<arr.length;i++){
			if(!arr[i].equals(str)){
			bw1.write(arr[i]);
			bw1.newLine();
			bw1.flush();
			flag = 1 ;
			}
		}
		if(flag==0){
			System.out.println("没有此人信息！");
		}
	}

	private static void Demo() {
		System.out.println("电话本信息管理");
		System.out.println("1.增加 ， 2.删除 ，3.修改 ，4.查询 ，5.退出");
		System.out.println("请输入您的选择：");
	}

	private static void Demo1(Scanner scr, BufferedWriter bw)
			throws IOException {
		System.out.println("--增加界面--");
		System.out.println("输入添加的数量：");
		int n = scr.nextInt() ;
		for(int i=0;i<n;i++){
		System.out.println("姓名：");
		String name = scr.next(); 
		System.out.println("年龄：");
		String age = scr.next() ; 
		System.out.println("电话号码：");
		String tele = scr.next() ; 
		String str = name + "," + age + "," + tele ;
		bw.write(str);
		bw.newLine();
		bw.flush();
		}
	}

}