java - 使用不同的键对列表进行排序

Question

这里的极端新手正在努力掌握列表可能排序的所有不同方式。假设我有一个对象列表，每个对象都有几个键，可用于在不同情况下进行排序。我从这个线程中得到了一些非常有用的信息: Java Interface Comparator static compare , 使用 Qwerky 的第一个示例作为创建的模型:

class Dog {
   private String name;
   private int age;
   private int height;
   private int weight;

   Dog(String n, int a, int b, int c){
      name = n;
      age = a;
      height = b;
      weight = c;
   }
   public String getDogName(){
      return name;
   }
   public int getDogAge(){
      return age;
   } 
   public int getDogHeight(){
      return height;
   }
   public int getDogWeight(){
      return weight;
   }
}

class DogComparator1 implements Comparator<Dog> {
   @Override
   public int compare(Dog d, Dog d1){
      return d.getDogAge() - d1.getDogAge();
   }
}
   class DogComparator2 implements Comparator<Dog> {
   @Override
   public int compare(Dog d, Dog d1){
      return d.getDogHeight() - d1.getDogHeight();
   }
}
   class DogComparator3 implements Comparator<Dog> { 
   @Override
   public int compare(Dog d, Dog d1){
      return d.getDogWeight() - d1.getDogWeight();
   }
}


public class Example{

   public static void main(String args[]){
      // Creat list of dog objects
      List<Dog> dogList = new ArrayList<>();

      // Add a buch of dogs to the list here
               .
               .

      // Create the Comparators
      DogComparator1 compare1 = new DogComparator1();
      DogComparator2 compare2 = new DogComparator2();
      DogComparator3 compare3 = new DogComparator3();


      // Sort the list using Comparators
      Collections.sort(list, compare1);  // Sort by age     
      Collections.sort(list, compare2);  // Sort by height
      Collections.sort(list, compare3);  // Sort by weight          
   }
}

但是，这似乎不对。我想我想将比较器定义拉到 Dog 类“内部”以很好地封装它们。但是，不知道该怎么做。

我走在正确的轨道上吗？如果是这样，将不胜感激帮助正确的语法。

Answer 1

您绝对是在正确的轨道上。

我只是将其添加到您的 Dog 类中:

public static final Comparator<Dog> COMPARE_BY_AGE = new Comparator<Dog>() {
    @Override
    public int compare(Dog d, Dog d1) {
        return d.getDogAge() - d1.getDogAge();
    }
};

public static final Comparator<Dog> COMPARE_BY_HEIGHT = new Comparator<Dog>() {
    @Override
    public int compare(Dog d, Dog d1) {
        return d.getDogHeight() - d1.getDogHeight();
    }
};

public static final Comparator<Dog> COMPARE_BY_WEIGHT = new Comparator<Dog>() {
    @Override
    public int compare(Dog d, Dog d1) {
        return d.getDogWeight() - d1.getDogWeight();
    }
};

然后用法如下:

    // Sort the list using Comparators
    Collections.sort(list, Dog.COMPARE_BY_AGE);  // Sort by age
    Collections.sort(list, Dog.COMPARE_BY_HEIGHT);  // Sort by height
    Collections.sort(list, Dog.COMPARE_BY_WEIGHT);  // Sort by weight