How to instantiate an object which is in a different class in java -

i trying create program saves of data given user save file , read file when user wants know information back.

now problem arises, when try call object instantiated in different method after call load() function.

import java.io.fileinputstream; import java.io.serializable; import java.io.fileoutputstream; import java.io.objectinputstream; import java.io.objectoutputstream; import java.util.scanner; import java.util.arraylist;  public class aibob  {     //array list of users     public static arraylist<user> userlist = new arraylist<user>();      public static void main (string args[]){          scanner scanner = new scanner(system.in);          system.out.println("hello! name bob, existing user or want make new account? ");            string userquantifier = scanner.nextline();         string[] check = {"exist","new"};          if(userquantifier.contains(check[0])){              system.out.println("can tell me name please?");             load();              newuser.load();                 // don't know how this.         }         else{             newuserpref(scanner);         }         string givenname = scanner.nextline();          for(int = 0; i<=10;i++){             if(userlist.get(i).getusername().contains(givenname)){             }         }     } } 

this load() function:

@suppresswarnings({ "unchecked", "unused" }) public static void load(){      try{         // open file read from, named savedobj.sav.         fileinputstream savefile = new fileinputstream("saveobj.sav");          // create objectinputstream objects save file.         objectinputstream save = new objectinputstream(savefile);          // restore.         // readobject() returns generic object, cast         // original class type.         // primitive types, use corresponding reference class.         arraylist <user> userlist = new arraylist<user>();         userlist =  (arraylist<user>) save.readobject();          // close file.         save.close(); // closes savefile.     }     catch(exception exc){         exc.printstacktrace(); // if there error, print info.     } } 

this newuserpref method save takes place

public static void newuserpref(scanner scanner){      system.out.println("hello! name bob, name? ");      string gname = scanner.nextline();      //create new user, assign name , user number      user newuser = new user(gname); //takes user input , saves user-name.      userlist.add(newuser); // creates new user in user class.      system.out.println("hi "+newuser.getusername()+"! can tell me how old you?");     int userage = scanner.nextint();     newuser.setage(userage);      system.out.println("if lactose intolerant, please write y/n ");     string input = scanner.next();           newuser.lactosefinder(input);      system.out.println("if want food glutten free, please write y/n ");     string otherinput = scanner.next();          newuser.gluttenfinder(otherinput);      system.out.println("if vegetarian or non-vegetraian, please write y/n ");     string dainput = scanner.next();             newuser.vegornonveg(dainput);      system.out.println("if vegan, please write y/n ");     string jainput = scanner.next();             newuser.vegan(jainput);     newuser.save();     try{  // catch errors in i/o if necessary.         // open file write to, named savedobj.sav.         fileoutputstream savefile=new fileoutputstream("saveobj.sav");          // create objectoutputstream put objects save file.         objectoutputstream save = new objectoutputstream(savefile);          // save.         save.writeobject(userlist);          // close file.         save.close(); // closes savefile.     }     catch(exception exc){         exc.printstacktrace(); // if there error, print info.     } } 

this user class's save , load method

public void save(){     try{  // catch errors in i/o if necessary.         // open file write to, named savedobj.sav.         fileoutputstream savefile=new fileoutputstream("savenewobj.sav");          // create objectoutputstream put objects save file.         objectoutputstream save = new objectoutputstream(savefile);          // save.         save.writeobject(getusername());         save.writeobject(getage());         save.writeobject(getlactoseintolerant());         save.writeobject(getglutten());         save.writeobject(getvegornonveg());         save.writeobject(getvegan());           // close file.         save.close(); // closes savefile.     }     catch(exception exc){         exc.printstacktrace(); // if there error, print info.     }  }  public void load(){     try{         // open file read from, named savedobj.sav.         fileinputstream savefile = new fileinputstream("savenewobj.sav");         // create objectinputstream objects save file.         objectinputstream save = new objectinputstream(savefile);          // restore.         // readobject() returns generic object, cast         // original class type.         // primitive types, use corresponding reference class.         username = (string) save.readobject();         age = (integer) save.readobject();         lactoseintolerant = (boolean) save.readobject();         glutenfree = (boolean) save.readobject();         vegetarian = (boolean) save.readobject();         vegan = (boolean) save.readobject();          // close file.         save.close(); // closes savefile.     }     catch(exception exc){         exc.printstacktrace(); // if there error, print info.     }    } 

this first post didn't know how code restriction there on website or should put code in 1 place or not. confused whether save/load function works or not. comment helpful. also, saved 1 file, hoping there way save different users in different files. thank in advance.

there few problems point out.

first, scope of variables.

in newuserpref() method, declared newuser user object: user newuser = new user(gname); in main method, tried use newuser again: newuser.load();

however, main method not able access newuser because local within newuserpref(). instead can declare static member object static user newuser; accessible entire class, , instantiate necessary. following example, though should decide instantiate it:

public static void main (string args[]){     ...     if(userquantifier.contains(check[0])){          system.out.println("can tell me name please?");         load();          newuser = new user(/*parameters*/);         newuser.load();     }     ... }  public static void newuserpref(scanner scanner){     ...     string gname = scanner.nextline();     newuser = new user(gname);     ... } 

second, naming conventions.

though isn't major issue cause errors, standard name variables , methods camelcase. start doing in future; people reading code.

hope helps, , let me know if need clarification.