JAVA创建和销毁对象的方法

public class NutritionFacts { 
  private final int servingSize; 
  private final int servings; 
  private final int calories; 
  private final int fat; 
  private final int sodium; 
  private final int carbohydrate; 
 
  public static class Builder { 
    //Required parameters 
    private final int servingSize; 
    private final int servings; 
 
    //Optional parameters - initialized to default values 
    private int calories   = 0; 
    private int fat     = 0; 
    private int carbohydrate = 0; 
    private int sodium    = 0; 
 
 
    public Builder(int servingSize, int servings) { 
      this.servingSize = servingSize; 
      this.servings = servings; 
    } 
 
    public Builder calories(int val){ 
      calories = val; return this; 
    } 
    public Builder fat(int val){ 
      fat = val; return this; 
    } 
    public Builder carbohydrate(int val){ 
      carbohydrate = val; return this; 
    } 
    public Builder sodium(int val){ 
      sodium = val; return this; 
    } 
 
    public NutritionFacts build(){ 
      return new NutritionFacts(this); 
    } 
  } 
 
  private NutritionFacts(Builder builder) { 
    servings   = builder.servings; 
    servingSize = builder.servingSize; 
    calories   = builder.calories; 
    fat     = builder.fat; 
    sodium    = builder.sodium; 
    carbohydrate = builder.carbohydrate; 
  } 
} 
 
//Client 
NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8). 
  calories(100).sodium(35).carbohydrate(27).build(); 

public enum Elvis { 
  INSTANCE; 
 
  public void leaveTheBuilding() {...} 
} 

//Noninstantiable utility class 
public class UtilityClass { 
  private UtilityClass() { 
    throw new AssertionError(); 
  } 
 
  ... // Remainder omitted 
}