Simulating login and registration functions with Java collections

Package com.linkage.login;

Import Java.util.HashMap;
Import Java.util.Iterator;
Import Java.util.Map;
Import Java.util.Scanner;
Import Java.util.Set;

public class Aggregate {
Static map<string, string> Map = new hashmap<> ();
Static String str1;
Static String str2;

@SuppressWarnings ("resource")
public static void Main (string[] args) {

while (true) {
Scanner Scanner = new Scanner (system.in);
Print ();
SYSTEM.OUT.PRINTLN ("Please select function:");
String str = Scanner.next ();
Switch (str) {
Case "1":
Login ();
Break
Case "2":
Register ();
Break
Case "3":
Show (map);
Break
Case "0":
System.exit (0);
Break
Default
SYSTEM.OUT.PRINTLN ("Wrong input!! ");
Break
}
}
}

Interface
public static void print () {
SYSTEM.OUT.PRINTLN ("--------------------* * * * * Management system--------------------");
System.out
. println ("1. Login function (login)");
System.out
. println ("2. Registration function (register)");
System.out
. println ("3. View (show)");
System.out
. println ("0. Exit");
SYSTEM.OUT.PRINTLN ("--------------------* * * * * Management system--------------------");
}

Detection
/**
* Repeat returned false is detected, otherwise true
* */
public static Boolean check () {
Input ();
if (Map.containskey (str1)) {
return false;
} else {
return true;
}
}

Login
public static void login () {
Input ();
if (Map.containskey (str1)) {
String value = Map.get (STR1);
if (Value.equals (str2)) {
SYSTEM.OUT.PRINTLN ("Login Successful! ");
} else {
SYSTEM.OUT.PRINTLN ("Password and username are inconsistent, please re-enter!") ");
}
} else {
System.out.println ("User name does not exist! ");
}
}

Registered
public static void register () {
if (check () = = True) {
Map.put (str1, str2);
SYSTEM.OUT.PRINTLN ("Registered successfully! ");
} else {
System.out.println ("User name already exists, please re-register!") ");
}
}

Show
public static void Show (Map<string, string> Map) {
set<string> keys = Map.keyset ();
Iterator<string> iter = Keys.iterator ();
while (Iter.hasnext ()) {
String key = Iter.next ();
String value = Map.get (key);
System.out.println ("key:" + key + ", Value:" + value);
}
}

Input
@SuppressWarnings ("resource")
public static void input () {
Scanner scanner1 = new Scanner (system.in);
System.out.println ("Please enter user name:");
STR1 = Scanner1.next ();
Scanner scanner2 = new Scanner (system.in);
System.out.println ("Please enter password:");
STR2 = Scanner2.next ();
}
}

Simulating login and registration functions with Java collections