目录
简单的一个登录程序
这是一个简单的将账号密码存在map里面方便验证登录的小程序，通过输入的account和键equals,输入的password和值equals，这样我们可以轻松判断账号和密码是否正确，只是账号密码才内存中储存，一旦程序终止，数据将被清空。上代码处的代码，我们将数据储存在磁盘中，这样将会一直保存下来，我们下次还可以继续登录，保证用户信息不会丢失。
package Lx22.Day0708;
import java.util.HashMap;
import java.util.Scanner;
public class Homework4 {
public static void main(String[] args) {
HashMap<String, String> User = new HashMap<>();
Scanner scanner = new Scanner(System.in);
while (true) {
System.out.println("请选择你的操作/1.注册操作2.登录操作");
int i = scanner.nextInt();
if (i == 1) {//注册方法
System.out.println("请输入账号");
String account = scanner.next();
System.out.println("请输入密码");
String passWord = scanner.next();
User.put(account, passWord);
}
if (i == 2) {//登录方法
System.out.println("请输入账号");
String account = scanner.next();
System.out.println("请输入密码");
String passWord = scanner.next();
if (!User.containsKey(account)) {//判断map里面有没有输入的键
System.out.println("账号错误或查无此账号");
}
else{
if(User.get(account).equals(passWord))
{
System.out.println("登陆成功");
break;
}
else System.out.println("密码错误");
}
}
}
}
}上代码
这个程序我们：
创建一个map，将map流入磁盘txt文件内；
map是双列结构，键值对，键不可重复（我们注册账号时可以省去检查申请的账号是否重复）方便验证账号密码登录。
package Lx22.Day0712;
import java.io.*;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Homework1Map {
static void login() throws IOException {//注册
Scanner scanner = new Scanner(System.in);
Map<String, String> map = new HashMap<>();
for (int i = 0; i < 5; i++) {
System.out.println("输入7 继续注册 输入其他终止注册");
int a = scanner.nextInt();
if (a == 7) {
System.out.println("请输入注册的账号");
String s1 = scanner.next();
System.out.println("请输入注册的密码");
String s2 = scanner.next();
map.put(s1, s2);//将账号密码存到map里面
} else break;
}
FileOutputStream out = new FileOutputStream("D:\\852\\账号密码.txt");
ObjectOutputStream Wout = new ObjectOutputStream(out);
Wout.writeObject(map);//将map流入到磁盘
out.flush();//刷新流
out.close();//关闭流
}
static void logon() throws IOException, ClassNotFoundException {//登录
Scanner scanner = new Scanner(System.in);
FileInputStream reader = new FileInputStream("D:\\852\\账号密码.txt");
ObjectInputStream oin = new ObjectInputStream(reader);
Map<String,String> map = (Map<String, String>)oin.readObject();//把map读出来
System.out.println("请输入账号");
String z = scanner.next();
System.out.println("请输入密码");
String m = scanner.next();
if (!map.containsKey(z)) {//判断map里面有没有输入的键
System.out.println("账号错误或查无此账号");
}
else{
if(map.get(z).equals(m))
{
System.out.println("登陆成功");
}
else System.out.println("密码错误");
}
}
}
package Lx22.Day0712;
import java.io.*;
import java.util.Scanner;
public class Homework1 {
/*2.实现注册，登录。
用户信息:用户名(userName),密码(password)
（1）注册功能：输入自己的个人信息，保存到文件。
（2）登录：输入自己的个人信息，与文件中的每行用户信息比较,判断登录是否成功.*/
public static void main(String[] args) throws IOException, ClassNotFoundException {
Scanner scanner = new Scanner(System.in);
while (true) {
System.out.println(" 输入1 进入注册功能");
System.out.println(" 输入2进入登录功能");
System.out.println(" 输入3退出");
int i = scanner.nextInt();
if (i == 1)
Homework1Map.login();
if (i == 2)
Homework1Map.logon();
if (i == 3)
break;
}
}
}
简陋的登录界面
送个小礼物：
给定一个目录,遍历此目录中所有的文件(如果有子级目录,也需要遍历其中的所有文件)
package Lx22.Day0711io;
import java.io.File;
public class Homework1 {
public static void main(String[] args) {
File f1 = new File("D://852");
sout(f1);
}
static void sout(File file) {
File[] list = file.listFiles();
for (File f2 : list) {
if (f2.isFile())
System.out.println(f2);
else {
sout(f2);
}
}
}
}
测试字节流read(),read(byte[] b) 和两个write(),write(byte[] b,int off,int length)的读写速度.
package Lx22.Day0711io;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class Homework2 {
public static void main(String[] args) throws IOException {
FileInputStream in1 = new FileInputStream("D:\\852\\1.txt");
byte [] bi = new byte[2];
long begin1 = System.currentTimeMillis();
while(in1.read()!=-1) {
}
long end1 = System.currentTimeMillis();
System.out.println("read耗时"+(end1-begin1)+"ms");
FileInputStream in2 = new FileInputStream("D:\\852\\1.txt");
long begin2 = System.currentTimeMillis();
while (in2.read(bi)!=-1){
}
long end2 = System.currentTimeMillis();
System.out.println("read(byte [])耗时"+(end2-begin2)+"ms");
System.out.println("---------------------分割-----------------------------------");
long bgein3 = System.currentTimeMillis();
try{
FileInputStream in3 = new FileInputStream("D://852//1.txt");
FileOutputStream out3 = new FileOutputStream("D://852//2.txt");
byte b [] = new byte[5];
int size = 0;
while((size = in3.read(b))!=-1)
{
out3.write(b, 0, size);
}
} catch(FileNotFoundException e){
e.printStackTrace();
System.out.println(e.getMessage());
}
long end3 = System.currentTimeMillis();
System.out.println("write(byte[])耗时"+(end3-bgein3)+"ms");
long bgein4 = System.currentTimeMillis();
try{
FileInputStream in4 = new FileInputStream("D://852//1.txt");
FileOutputStream out4 = new FileOutputStream("D://852//2.txt");
int b=0;
while((b=in4.read())!=-1)
{
out4.write(b);
}
} catch(FileNotFoundException e){
e.printStackTrace();
System.out.println(e.getMessage());
}
long end4 = System.currentTimeMillis();
System.out.println("write()耗时"+(end4-bgein4)+"ms");
}
}