java Comparable整理

1. 自定义类比较

Person

public class Person{
    String name;
    int score;
    Person(String name, int score) {
        this.name = name;
        this.score = score;
    }
    @Override
    public String toString() {
        return this.name + "," + this.score;
    }
}

TestMain1

public class TestMain1
{
    public static void main(String[] args) {

        Person[] ps = new Person[] {
                new Person("Bob", 61),
                new Person("Alice", 88),
                new Person("Lily", 75),
        };
        Arrays.sort(ps);
        System.out.println(Arrays.toString(ps));
    }
}

运行结果：因为我们的Person类无法进行Comparable转换出错。

Exception in thread "main" java.lang.ClassCastException: com.luoyu.aiyu.luo1.Person cannot be cast to java.lang.Comparable
    at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:320)
    at java.util.ComparableTimSort.sort(ComparableTimSort.java:188)
    at java.util.Arrays.sort(Arrays.java:1246)
    at com.luoyu.aiyu.luo1.TestMain1.main(TestMain1.java:14)

修改后的Person类

public class Person implements Comparable{
    String name;
    int score;
    Person(String name, int score) {
        this.name = name;
        this.score = score;
    }
    @Override
    public String toString() {
        return this.name + "," + this.score;
    }

    @Override
    public int compareTo(Person o) {
        return this.name.compareTo(o.name);
    }
}

然后执行正常。。。

2. Integer 关于Comparable的实现理解

 1. 首先Integer 实现了Comparable 

2. 可以看到Comparable里面只有一个方法compareTo()

 3. 这里就是compareTo的实现了。