Avoid having to write field declarations, toString(), equals() or hashCode() for your classes

1. Create 2-tuple (pair) class thats generic and overridable:

   public class _<ONE, TWO>
   {
       protected final ONE $1;
       protected final TWO $2;
   
       public _(final ONE _1, final TWO _2)
       {
           this.$1 = _1;
           this.$2 = _2;
       }
   
       public boolean equals(final Object obj)
       {
           return this == obj || obj != null && getClass() == obj.getClass() && $1.equals(((_<?, ?>) obj).$1) && $2.equals(((_<?, ?>) obj).$2);
       }
   
       public int hashCode()
       {
           final int prime = 31;
           int result = 1;
           result = prime * result + ($1 == null ? 0 : $1.hashCode());
           result = prime * result + ($2 == null ? 0 : $2.hashCode());
           return result;
       }
   
       public String toString()
       {
           return format("[%s,%s]",$1,$2);
       }
   
   }

2. Override with appropriate fields:

   public class Product extends _<String, String>
     {
         public Product(final String id, final String name)
         {
             super(id, name);
         }
   
         public String id()
         {
             return $1;
         }
   
         public String name()
         {
             return $2;
         }
     }

• You can do the same with singles, triples and quadruples for classes with 1, 3 and 4 fields respectively (beyond 4 it's not worth it). I've found that pairs (ie classes with two dependencies) are by far the most frequent.

• Improve: check class of fields to optimise hashing function

Inspired by Andy Parker's Equalable