- 需求: 有Dog和Cat类,对Dog[],Cat[]排序，满足可扩展性、灵活性、易维护性
- v1: 在Cat类 Dog类定义方法compareTo
// Cat类
public class Cat {
private int weight, height;
public Cat(int weight, int height) {
this.weight = weight;
this.height = height;
}
public int compareTo(Cat c) {
if (this.weight < c.weight) return -1;
else if(this.weight > c.weight) return 1;
else return 0;
}
@Override
public String toString() {
return "Cat{" +
"weight=" + weight +
", height=" + height +
'}';
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
}
// 排序类
public class SorterCat {
/**
* 思路: 循环数组，取出数组的每一个值，与大于这个值下标的值比较，取出最小值,
* 最小值与当前的数组值对换
* @param arr
*/
public static void sort(Cat[] arr) {
for (int i = 0; i < arr.length; i++) {
int minPos = i;
for (int j = i + 1; j < arr.length; j++) {
minPos = arr[j].compareTo(arr[minPos]) == -1 ? j : minPos;
}
swap(arr, i, minPos);
}
}
// 交换数组不同下标的值
static void swap(Cat[] arr, int i, int j) {
Cat temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
public static void main(String[] args) {
Cat[] arr = {new Cat(3,3), new Cat(5, 5),new Cat(1, 1) };
sort(arr);
for (Cat item : arr) {
System.out.println(item);
}
}
}
- v2: v1中的compareTo可以抽象comparable接口
// cat类
public class CatC implements Comparable<CatC> {
private int weight, height;
public CatC(int weight, int height) {
this.weight = weight;
this.height = height;
}
@Override
public String toString() {
return "Cat{" +
"weight=" + weight +
", height=" + height +
'}';
}
@Override
public int compareTo(CatC c) {
if (this.weight < c.weight) return -1;
else if(this.weight > c.weight) return 1;
else return 0;
}
}
// dog类
public class DogC implements Comparable<DogC> {
private int food;
public DogC(int food) {
this.food = food;
}
@Override
public int compareTo(DogC d) {
if (this.food < d.food) return -1;
else if (this.food > d.food) return 1;
else return 0;
}
@Override
public String toString() {
return "DogC{" +
"food=" + food +
'}';
}
}
public class SorterComparable {
/**
* 思路: 循环数组，取出数组的每一个值，与大于这个值下标的值比较，取出最小值,
* 最小值与当前的数组值对换
* @param arr
*/
public static void sort(Comparable[] arr) {
for (int i = 0; i < arr.length; i++) {
int minPos = i;
for (int j = i + 1; j < arr.length; j++) {
minPos = arr[j].compareTo(arr[minPos]) == -1 ? j : minPos;
}
swap(arr, i, minPos);
}
}
// 交换数组不同下标的值
static void swap(Comparable[] arr, int i, int j) {
Comparable temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
//main
@Test
public void testComparable(){
Comparable[] dogs = {new DogC(3),new DogC(2),new DogC(1)};
SorterComparable.sort(dogs);
for (Comparable dog : dogs) {
System.out.println(dog);
}
System.out.println("========");
Comparable[] cats = {new CatC(3,2),new CatC(2,1),new CatC(1,10)};
SorterComparable.sort(cats);
for (Comparable cat : cats) {
System.out.println(cat);
}
}
- v3: 因为compareTo中的比较器,可能随时需要变化,v2不能满足这个需求,抽象出来Comparator接口，可以传递比较行为(由使用者指定),这样就灵活很多
/**
* 比较器接口实现策略模式
* @param <T>
*/
public interface Comparator<T> {
int compare(T o1, T o2);
}
// Cat类
public class Cat {
private int weight, height;
public Cat(int weight, int height) {
this.weight = weight;
this.height = height;
}
@Override
public String toString() {
return "Cat{" +
"weight=" + weight +
", height=" + height +
'}';
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
}
public class Sorter<T> {
/**
* 思路: 循环数组，取出数组的每一个值，与大于这个值下标的值比较，取出最小值,
* 最小值与当前的数组值对换
* @param arr
*/
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);
}
}
// 交换数组不同下标的值
void swap(T[] arr, int i, int j) {
T temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
@Test
public viod testComparator(){
Sorter<Cat> sorter = new Sorter<>();
Cat[] arr = {new Cat(3,1), new Cat(2,9), new Cat(1,3)};
Comparator<Cat> comparator = (o1, o2) -> {
if (o1.getHeight() < o2.getHeight()) return -1;
else if (o1.getHeight() > o2.getHeight()) return 1;
else return 0;
};
Comparator<Cat> comparator1 = (o1, o2) -> {
if (o1.getWeight() < o2.getWeight()) return -1;
else if (o1.getWeight() > o2.getWeight()) return 1;
else return 0;
};
// 这里可随意切换比较器,实现了灵活扩展
sorter.sort(arr,comparator);
// sorter.sort(arr,comparator1);
for (Cat c : arr) {
System.out.println(c);
}
}
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