Java Objects require non null

import java.util.Objects;

class Item {/*from   w  w  w .jav  a  2  s . c  o  m*/
   private String name;
   private int partNumber;

   public Item() {
      this("Widget", 0);
   }

   public Item(String name, int partNumber) {
      this.name = Objects.requireNonNull(name);
      this.partNumber = partNumber;
   }

   public String getName() {
      return name;
   }

   public void setName(String name) {
//      this.name = Objects.requireNonNull(name);
        this.name = Objects.requireNonNull(name, "The name field requires a non-null value");        
   }

   public int getPartNumber() {
      return partNumber;
   }

   public void setPartNumber(int partNumber) {
      this.partNumber = partNumber;
   }

   @Override
   public boolean equals(Object obj) {
      if (obj == null) {
         return false;
      }
      if (getClass() != obj.getClass()) {
         return false;
      }
      final Item other = (Item) obj;
      if (!Objects.equals(this.name, other.name)) {
         return false;
      }
      if (this.partNumber != other.partNumber) {
         return false;
      }
      return true;
   }

   @Override
   public int hashCode() {
      int hash = 7;
      hash = 47 * hash + Objects.hashCode(this.name);
      hash = 47 * hash + this.partNumber;
      return hash;
   }

   @Override
   public String toString() {
      return name + " - " + partNumber;
   }

}

public class Main {

   public static void main(String[] args) {
      Item item1 = new Item("CSS", 2200);
      Item item2 = new Item("CSS2", 1200);
      Item item3 = new Item("HTML", 1100);
      Item item4 = null;

      System.out.println("item1 equals item1: " + item1.equals(item1));
      System.out.println("item1 equals item2: " + item1.equals(item2));
      System.out.println("item1 equals item3: " + item1.equals(item3));
      System.out.println("item1 equals item4: " + item1.equals(item4));

      item2.setName(null);
      System.out.println("item1 equals item2: " + item1.equals(item2));

   }

}