6.Java----比较器

简介

Comparable和Comparator接口都是为了对类进行比较，众所周知，诸如Integer，double等基本数据类型，java可以对他们进行比较，而对于类的比较，需要人工定义比较用到的字段比较逻辑。可以把Comparable理解为内部比较器，而Comparator是外部比较器，基本的写法如下：

Comparable(实现Comparable接口，并重写CompareTo方法)

public class ComparableTest {
    @Test
    public void test1(){
        Person[] pList = new Person[]{
                new Person("test1",11),
                new Person("test2",55),
                new Person("test3",33)
        };
        System.out.println(Arrays.toString(pList));
        Arrays.sort(pList);
        System.out.println(Arrays.toString(pList));
    }

   

class Person implements Comparable{
    private String name;
    private int age;

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public int compareTo(Object o) {
        if(o instanceof Person){
            Person p = (Person)o;
            if(this.age > p.age)
            {
                return 1;
            }else if(this.age < p.age){
                return -1;
            }else{
                return 0;
            }
        }
        throw new RuntimeException("类型不正确");
    }
}

Comparator(生成一个Comparator对象，并重写compare方法)

 @Test
    public void test2(){
        Person[] pList = new Person[]{
                new Person("test1",11),
                new Person("test2",55),
                new Person("test3",33)
        };
        System.out.println(Arrays.toString(pList));
        Arrays.sort(pList, new Comparator<Person>() {
            @Override
            public int compare(Person o1, Person o2) {
                if(o1.getAge() > o2.getAge()){
                    return -1;
                }else if(o1.getAge() < o2.getAge()){
                    return 1;
                }else{
                    return 0;
                }
            }
        });
        System.out.println(Arrays.toString(pList));

    }
}