corejava-programming: How to write code for reset password in core Java?

I´ld explain it in simple manner using properties file. But practically you must go with some database and Java jdbc. Instead of using database, I used properties file for a reference which is user.properties. In which key refers user name and value refers password for respective user.

user.properties:
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User123=Password123
User456=Password456
User789=Password789


ResetPassword.java:
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import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Properties;
import java.util.Scanner;

public class ResetPassword {
private static Scanner input=new Scanner(System.in);
private static String filePath="D:/in/anyforum/user.properties";
public static void main(String[] args) {
System.out.println("Please Enter your user name:");
String userName= input.nextLine();
System.out.println("Please Enter your old password:");
String password= input.nextLine();
boolean isLogin = login(userName, password);
if(isLogin){
System.out.println("Enter new password:");
String newPassword = input.nextLine();
System.out.println("Confirm password:");
String confirmPassword = input.nextLine();
if(newPassword.equals(confirmPassword)){
//use JDBC instead
Properties properties=getProperties();
properties.setProperty(userName, newPassword);
saveProperties(properties);
System.out.println("Password Reset Successfully!");
}else{
System.out.println("New password and confirm password doesn´t match");
}
}else{
System.out.println("Sorry! Invalid Username Password.");
}
}

public static boolean login(String userName, String password){
boolean isLogin=false;
//use JDBC instead
Properties properties=getProperties();
String actualPassword=properties.getProperty(userName);
if(password.equals(actualPassword))
isLogin=true;

return isLogin;
}

private static Properties getProperties(){
Properties properties = null;
try{
properties=new Properties();
FileInputStream fis= new FileInputStream(filePath);
properties.load(fis);
fis.close();
}catch (Exception e) {
e.printStackTrace();
}
return properties;
}

private static void saveProperties(Properties properties){
try{
FileOutputStream fos= new FileOutputStream(filePath);
properties.store(fos, null);
}catch (Exception e) {
e.printStackTrace();
}
}

}