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Comparable和Comparator都是用来实现比较的#xff0c;一般用于集合中元素的比较 基本包装类型#xff0c;Integer、Long以及String都实现了Comparable接口#xff0c;该接口的排序逻辑必须写在比较对象中#xff0c;所以又叫自然排序 我们一般集合排序使用的Col…一、概述
Comparable和Comparator都是用来实现比较的一般用于集合中元素的比较 基本包装类型Integer、Long以及String都实现了Comparable接口该接口的排序逻辑必须写在比较对象中所以又叫自然排序 我们一般集合排序使用的Collections.sort()默认使用的就是Comparable public static T extends Comparable? super T void sort(ListT list) {list.sort(null);}当然我们也可以指定比较器这里使用的就是Comparator了 public static T void sort(ListT list, Comparator? super T c) {list.sort(c);}二、实际使用
1、Comparable
定义了对象Forlan实现了Comparable接口重写了compareTo(对象)方法
public class Forlan implements ComparableForlan {private String name;/*** 身高*/private int height;/*** 体重*/private int weight;public Forlan(String name, int height, int weight) {this.name name;this.height height;this.weight weight;}Overridepublic String toString() {return Forlan{ name name \ , height height , weight weight };}/*** 比较身高*/Overridepublic int compareTo(Forlan forlan) {return this.height - forlan.height;}
}验证比较器
ListForlan list new ArrayList();
Forlan forlan1 new Forlan(身高低体重中, 170, 130);
Forlan forlan2 new Forlan(身高高体重低, 180, 120);
Forlan forlan3 new Forlan(身高中体重高, 175, 140);
list.add(forlan1);
list.add(forlan2);
list.add(forlan3);
Collections.sort(list);
System.out.println(list);// 运行结果
[Forlan{name身高低体重中, height170, weight130}, Forlan{name身高中体重高, height175, weight140}, Forlan{name身高高体重低, height180, weight120}]
2、Comparator
定义了对象ForlanW实现了Comparator接口重写了compare(T o1, T o2)方法
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;public class ForlanW implements ComparatorForlanW{private String name;/*** 身高*/private int height;/*** 体重*/private int weight;public ForlanW(String name, int height, int weight) {this.name name;this.height height;this.weight weight;}public String getName() {return name;}public void setName(String name) {this.name name;}public int getHeight() {return height;}public void setHeight(int height) {this.height height;}public int getWeight() {return weight;}public void setWeight(int weight) {this.weight weight;}Overridepublic String toString() {return ForlanComparator{ name name \ , height height , weight weight };}Overridepublic int compare(ForlanW o1, ForlanW o2) {return o1.height - o2.height;}public static void main(String[] args) {ListForlanW list new ArrayList();ForlanW forlan1 new ForlanW(身高低体重中, 170, 130);ForlanW forlan2 new ForlanW(身高高体重低, 180, 120);ForlanW forlan3 new ForlanW(身高中体重高, 175, 140);list.add(forlan1);list.add(forlan2);list.add(forlan3);// Collections.sort(list, new HeightComparator()); // 身高比较// Collections.sort(list, new WeightComparator()); // 体重比较// 身高比较Collections.sort(list, (ForlanW o1, ForlanW o2) - {return o1.height - o2.height;});System.out.println(list);}
}class HeightComparator implements ComparatorForlanW {Overridepublic int compare(ForlanW o1, ForlanW o2) {return o2.getHeight() - o1.getHeight();}
}class WeightComparator implements ComparatorForlanW {Overridepublic int compare(ForlanW o1, ForlanW o2) {return o2.getWeight() - o1.getWeight();}
}验证比较器
ListForlanComparator list new ArrayList();
ForlanComparator forlan1 new ForlanComparator(身高低体重中, 170, 130);
ForlanComparator forlan2 new ForlanComparator(身高高体重低, 180, 120);
ForlanComparator forlan3 new ForlanComparator(身高中体重高, 175, 140);
list.add(forlan1);
list.add(forlan2);
list.add(forlan3);
// Collections.sort(list, new HeightComparator()); // 身高比较
// Collections.sort(list, new WeightComparator()); // 体重比较
// 身高比较
Collections.sort(list,(ForlanComparator o1, ForlanComparator o2)-{return o1.height - o2.height;
});
System.out.println(list);// 运行结果
[ForlanComparator{name身高低体重中, height170, weight130}, ForlanComparator{name身高中体重高, height175, weight140}, ForlanComparator{name身高高体重低, height180, weight120}]三、总结
1、相同点
Comparable和Comparator都是用于比较排序
2、不同点
接口所在包不同java.lang.Comparable、java.util.Comparator比较逻辑不同Comparable的在类中Comparator可以在类中也可以在类外但在类中意义不大简单来说Comparable是内部比较器Comparator是外部比较器排序方法不同Comparable重写方法compareTo(T o)Comparator重写方法compare(T o1, T o2)在Collections.sort()中使用不同一个参数默认是Comparable自然排序二个参数需要传入Comparator外部排序排序规则数量限制不同Comparable唯一Comparator可以有多个
