java - Why my program is failing with null pointer exception -

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• what nullpointerexception, , how fix it? 12 answers

i working on test assignment have take name , phone number user ans save them arraylist. created 3 classes

• contacts: store contact details.
• mobilephone: store contacts objects.
• mobilemain : begins program execution.

following content of classes:

contacts.java

    package mobilephone;      public class contacts {     private int number;     private string name;      public contacts(string name,int number ) {         this.name = name;         this.number = number;     }      public int getnumber() {         return number;     }      public void setnumber(int number) {         this.number = number;     }      public string getname() {         return name;     }      public void setname(string name) {         this.name = name;     }  } 

mobilephone.java

package mobilephone;  import java.util.arraylist;  public class mobilephone {     private arraylist<contacts> phonebook = new arraylist<contacts>();      public void addphone(contacts contact) {         phonebook.add(contact);     }      public void showcontacts(){         for(int i=0 ;i< phonebook.size();i++){         system.out.println(phonebook.get(i).getname()+" => "+phonebook.get(i).getnumber());         }     }   } 

mobilemain.java

package mobilephone;  import java.util.scanner;  public class mobilemain {     static scanner scanner = new scanner(system.in);     static contacts contacts;     static mobilephone mobilephone;     public static void main(string[] args){         addcontact();                mobilephone.showcontacts();     }      static void addcontact(){         system.out.print("enter name: ");         string name= scanner.nextline();         system.out.println("enter phone number");         int number= scanner.nextint();         mobilephone.addphone(new contacts(name,number));      }   } 

but on executing main class getting below error.

enter name: fgsdg enter phone number 234234 exception in thread "main" java.lang.nullpointerexception     @ mobilephone.mobilemain.addcontact(mobilemain.java:19)     @ mobilephone.mobilemain.main(mobilemain.java:10) 

i verified object passing @ line 19 in mobilemain.java not null

mobilephone null, have initialize variable first:

static mobilephone mobilephone = new mobilephone(); 

only can use addphone