I can see you are probably quite new to Java - so you may be lacking a few fundamentals.

Probably best to just pass the string in as a parameter to the method in your case e.g.

public void WelcomeAgent(String lastName) {

and when you call the method, send that value in e.g.

AgentObject.WelcomeAgent(userinput);    

Btw, a few convention tips. Variables and functions should start with a lower case . e.g.

String lastName;

and

Citizen citizen = new Citizen();

If you're trying to call a variable from another class, you have several options:

1) Declare the variable in the other class as static:

public class Estadisticas {

  public static String c1 = "Tu personaje";
  ...
}

So in the other class, you can just call the string like so:

public class Start extends Estadisticas {
  public static void main() {
    System.out.println(Estadisticas.c1);
  }
}

2) Have the stats method return the string:

public String stats() {

  final String c1 = "Tu personaje";
  final int Nivel = 1;
  final int Salud = 50;
  final int Ataque = 2;
  final int Defensa = 1;

  final String c2 = "Primer monstruo - Rata rabiosa";
  final int SaludM1 = 2;
  final int AtaqueM1 = 1; 

  return c1;
}

So you can do this:

public class Start extends Estadisticas {
  public static void main() {
    Estadisticas es = new Estadisticas();
    System.out.println(es.stats());
  }
}

3) Use an accessor method and instance variables:

public class Estadisticas {
  private String c1, c2;
  private int nivel, salud, ataque, defensa, saludM1, ataqueM1;

  public void stats() {
    c1 = "Tu personaje";
    nivel = 1;
    salud = 50;
    ataque = 2;
    defensa = 1;

    c2 = "Primer monstruo - Rata rabiosa";
    saludM1 = 2;
    ataqueM1 = 1; 
  }

  //accessor method
  public String getc1() {
    return c1;
  }
}

So in the other class you can use:

public class Start extends Estadisticas {
  public static void main() {
    Estadisticas es = new Estadisticas();
    System.out.println(es.getc1());
  }
}

So change main in the Address class into a function like so:

public class Address {

    public static String Macgen() {
        Random rand = new Random();

        String result1 = String.format("%x", (int) (Math.random() * 100));
        String result2 = String.format("%x", (int) (Math.random() * 100));
        String result3 = String.format("%x", (int) (Math.random() * 100));
        String result4 = String.format("%x", (int) (Math.random() * 100));
        String result5 = String.format("%x", (int) (Math.random() * 100));
        String result6 = String.format("%x", (int) (Math.random() * 100));

        String macAddress = (result1 + ":" + result2 + ":" + result3 + ":" +

        result4 + ":" + result5 + ":" + result6);
        return macAdress;
    }
}

Call this function like so

public class NetworkDevice {

public static void main (String args[]){
    System.out.println(Address.Macgen());

}

The default scope is package-private. Use the public modifier on the String declaration

public String productId;

I want the user input from this class and bring into another class and use the number variable for a If statement.

It is simple take a look at below example(make sure to add both classes in one package different java files as Player.java and ExampleClass.java),

This is the class that Scanner has:

import java.util.*;

public class Player{
    public static void main (String [] args){

        Scanner getInput = new Scanner(System.in);
        System.out.print("Input a number");
        //you can take input as integer if you want integer value by nextInt()
        String number = getInput.nextLine();

        ExampleClass obj = new ExampleClass(number);
        obj.checkMethod();
    }
}

This is the class that check number:

public class ExampleClass{
    int number;
    public ExampleClass(String number){
        try{
            //If you want to convert into int
            this.number = Integer.parseInt(number);
        }catch(NumberFormatException e){
            System.out.println("Wrong input");
        }
    }

    public void checkMethod(){
        if(number > 5){
            System.out.println("Number is greater.");
        }else{
            System.out.println("Number is lesser.");
        }
    }
}

Few thing to mention:

Your example code contains syntax errors, fix those first.

1. If you want integer you can use getInput.nextInt() rather than getInput.nextLine().
2. You can create getter and setters to set vaues and get values. In my example I just only set value through the constructor.
3. Use proper naming convention.
4. In my example I convert the String into integer inside the constructor and wrap with try-catch block to prevent from NumberFormatException(If you input character or something you can see wrong input will print). Sometimes in variaus situation it is not good to use try-catch in constructor. To learn more about this, please read Try / Catch in Constructor - Recommended Practice.

I'm a bit confused on what is being asked but I'll try to answer.

I would declare the field private String senderNum and the method public String getSenderNum(){return senderNum;} and remove the declaration of String in:

String senderNum = phoneNumber;
message = currentMessage.getDisplayMessageBody();

then in MainActivity.java call getSenderNum() where it is needed.

It seems as if you want to obtain the character in your main class after the survey has completed, so it can be printed out in the main method.

You can simply change your void survey method to a String survey method, allowing you to return a value when that method is called:

class CharacterSurvey {
    public String takeSurvey() {
        //ask questions, score points
        String character = null;

        if(firstPerson == outcome) {
            character = "First Person";
        }

        return character;
    }
}

Now, when you call this method, you can retrieve the value returned from it:

class Main {
    public static void main(String[] args) {
        CharacterSurvey survey = new CharacterSurvey();

        String character = survey.takeSurvey();
        System.out.println(character);
    }
}

Create an instance variable:

public class MyClass {

    private String str;

    public void method1() {
        // change str by assigning a new value to it
    }

    public void method2() {
        // the changed value of str is available here
    }

}

There is no need to pass array to , since ActivityTo is also an activity so can fetch the resources array here too

public class ActivityTo extends ListActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);

        String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);

        ArrayAdapter<String> adapterCityBreak = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayCityBreak);

        ListView myview = getListView();

        myview.setAdapter(adapterCityBreak);

    }
}

To remove current error,

either do this

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    con=this;
}

or

use this in MainActivity because con is not initialized

  String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);

instead of

  String [] arrayCityBreak = con.getResources().getStringArray(R.array.citybreak);

If I understood your question, you have an activity that gets some information and wanna use them in another activity. so you can use intents like this code in the first activity when you want to go to second class:

Intent i = new Intent(ActivityOne.this, ActivityTwo.class);
i.putExtra("value", "some string");
startActivity(i);

in second activity use this code:

Bundle extras = getIntent().getExtras();
// get data via the key
String value1 = extras.getString("value");

you can have extras as many as you want

Both techniques are terrible, but using the getter is the common (and safer) practice.

In order to access a public data member (a.k.a. public field or public property) of a class, you must know the implementation details of the class (the data member name and the data member type). This is a bad thing; it breaks the OOP concept "information hiding" and increases "coupling".

Using a getter is also bad (as in a bad OOP practice) because objects are not just wrappers around data; objects are supposed to encapsulate functionality and data. "store this here value so I can get it later" is not functionality; it is hoot functionality (as in a monkey in a cage hooting). Getters are; however, an accepted practice in java (and other OOP-lite languages like c++ and c#).

Lest you think I am some ivory tower purest, of course I use getters; I use java, so I use getters.

Getters are fine for getting the work done (no pun), just don't walk around believing that "I R gud OOP Prgmr", because if you use getters you are not a "good oop programmer", you are just a programmer who gets work done.

Edit: Perhaps a better way.

The better way is to not use getters, but to instead design your classes so they expose functionality not data. In practice, there is a point where this breaks down; for example, if you need to display an address on a JSP page, you put a bean in the request (or session or blah) with the address and expose the values using getters. A "more oop pure" way would be to put a bean that exposed "display the address on a jsp" functionality.

Edit2: Perhaps a better example.

Say I work for a phone company, in the USA, and I have an object that represents a customers phone number. This might look like the following:

public class CustomerPhoneNumber
{
  private String npa; // numbering plan area (google search nanp for more details)
  private String nxx; // exchange.
  private String serviceNumber;

  public String toString()
  {
    return "(" + npa + ") " + nxx + "-" + serviceNumber;
  }

  public boolean equals(Object object)
  {
    ... standard equals implementation (assume this works)
  }
}

Now say I get a phone number as an input from a web page in the form String inputPhoneNumber. For the purposes of discussion, the class that receives this input is called "the servlet".

How can I answer this question: "Is the input phone number in my list of CustomerPhoneNumber objects?"

Option 1 is make the npa, nxx, and serviceNumber data members public and access them. This is terrible.

Option 2 is provide getters for npa, nxx, and service number and compare them with the input. Also terrible, too many internal details exposed.

Option 3 is provide a getter that returns the formatted phone number (I called this toString() above). This is smarter but still terrible because the servlet has to know the format that will be used by the getter and ensure that the input is formatted the same way.

Option 4 (I call this "Welcome to OOP") provide a method that takes a String and returns true if that matches the customer service number. This is better and might look like this (the name is long, but sufficient for this example):

public boolean doesPhoneNumberMatchThisInput(final String input)
{
   String formattedInput;
   String formattedCustomerPhoneNumber = npa + nxx + serviceNumber;

   formattedInput = ... strip all non-digits from input.

   return StringUtils.equals(formattedCustomerPhoneNumber, formattedInput);
}

This is the winner because no implementation details are exposed. Also the toString can be used to output the phone number on a JSP page.

StringUtils is part of Apache Commons Lang.

I think you misunderstood the main method, maybe I am wrong, however only one main method is executed.

If you run Sample2.main - on Sample1 you are not setting a name so it is null (Sample1.main is never executed).

If you run Sample1.main - Sample1 is created and assigned a name.

So either assign the name in the Sample2.main:

public static void main(String[] args) {
  Sample1 n2= new  Sample1();
  n2.setName("xxx");
  System.out.println(n2.getName());
}

or do it via constuctor.

public class Sample1 {
  private final String name;
  public String getName() {
    return name;
  }
  public Sample1(String name) {
    this.name = name;
  }
}