AdressBuilder.java

public class AddressBuilder { 
   ... 
   public Address build() {
    Address address = new Address(); 
    address.setStreet(validateStreet(street)); 
    ... 
    return address; 
   } 
} 

public class Address { 
   ... 
   Address() { 
    // reduce visibility of the default constructor 
    } 

public String getStreet() {
   return street;
   }

   // may just be used by the builder 
   void setStreet(String initialStreet) {
    street = initialStreet;
   } 
   ... 
}