public class OuterClass {
  static class StaticInnerClass {
    ...
  }
}

public class OuterClass {
  class InnerClass {
    ...
  }
}

//定义成员内部类的方式一
OuterClass test = new OuterClass();
InnerClass innerA = test.new InnerClass();
//定义成员内部类的方式二
OuterClass.InnerClass innerB = new OuterClass().new InnerClass();

public void methodInnerClass() {
  class InnerClass {
    ...
  }
  InnerClass A = new InnerClass();
}

Button button = new Button();
button.addActionListener(new ActionListener() {
  @Override
  public void actionPerformed(ActionEvent e) {
    ...       
  }
});

public class OuterClass {
  static class StaticInnerClass {
    ...
  }
}

//Builder Pattern
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) {
    servingSize = builder.servingSize;
    servings = builder.servings;
    calories = builder.calories;
    fat = builder.fat;
    sodium = builder.sodium;
    carbohydrate = builder.carbohydrate;
  }
}

NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8).calories(100).sodium(35).carbohydrate(27).build();