Strategy mode

Java23 Learning notes of design patterns ：https://www.cnblogs.com/meet/p/5116504.html

 

according to java Design principles , We should close the modification , Open to expansion . So we need to try not to modify the source code .
For the top Cat class , We want to follow weight Sort , If we want to follow height Sort it out ？
So we define our own Comparable, Use generics to control the type of incoming parameters .

public interface Comparator<T> {
    int compare(T o1,T o2);
}

public class Sorter<T> {


    public  void sort(T[] arr,Comparator<T> comparator) {
        for (int i = 0; i < arr.length; i++) {
            int minPos = i;
            for (int j = i + 1; j < arr.length; j++) {
                minPos =comparator.compare(arr[j],arr[minPos]) == -1 ? j : minPos;
            }
            swap(arr, i, minPos);
        }
    }

     void swap(T[] arr, int i, int j) {
        T temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
}

public class Cat {
    int weight;
    int height;

    public Cat(int weight, int height) {
        this.weight = weight;
        this.height = height;
    }

    @Override
    public String toString() {
        return "Cat{" +
                "weight=" + weight +
                ", height=" + height +
                '}';
    }

}

public class CatComparator implements  Comparator<Cat>{

    @Override
    public int compare(Cat o1, Cat o2) {
        if(o1.weight<o2.weight){
            return -1;
        }else if(o1.weight>o2.weight){
            return 1;
        }else {
            return 0;
        }
    }
}

import com.sun.xml.internal.ws.api.model.wsdl.WSDLOutput;

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        Cat[] cats={new Cat(3,3),new Cat(1,1),new Cat(5,5)};
        Sorter<Cat> sorter=new Sorter<Cat>();
        sorter.sort(cats, new CatComparator());
        System.out.println(Arrays.toString(cats));
    }

}

You can see , We are main Function :

sorter.sort(cats, new CatComparator());

new CatComparator() Into Cat Class comparison strategy , according to weight Sort . If you want to modify the sorting strategy , Just change the policy class .

This is the strategy model .