Java中Comparator与Comparable排序的区别详解

public class CompareDemo implements Comparable<CompareDemo>{
    int code;
    int age;
    public CompareDemo(int code, int age) {
        this.code = code;
        this.age = age;
    }
    @Override
    public int compareTo(CompareDemo o) {
        if(code == o.code){
            return 0;
        }else if(code<o.code){
            return -1;
        }else{
            return 0;
        }
    }
}

List<CompareDemo> list = new ArrayList<CompareDemo>(){{
    add(new CompareDemo(10,20));
    add(new CompareDemo(12,30));
    add(new CompareDemo(11,10));
}};
list.forEach(compareDemo -> System.out.println(compareDemo.code));
//默认根据code进行升序比较
list.sort(null);
list.forEach(compareDemo -> System.out.println(compareDemo.code));

list.sort(new Comparator<CompareDemo>() {
    @Override
    public int compare(CompareDemo o1, CompareDemo o2) {
        if (o1.age == o2.age) {
            return 0;
        } else if (o1.age < o2.age) {
            return -1;
        } else {
            return 1;
        }
    }
});
list.forEach(compareDemo -> System.out.println(compareDemo.age));

list.sort(new Comparator<CompareDemo>() {
    @Override
    public int compare(CompareDemo o1, CompareDemo o2) {
        return Integer.compare(o1.age,o2.age);
    }
});

list.sort(Comparator.comparingInt(o -> o.age));

list.sort(new Comparator<CompareDemo>() {
    @Override
    public int compare(CompareDemo o1, CompareDemo o2) {
        return Integer.compare(o2.age,o1.age);
    }
});

list.sort(Comparator.comparingInt(o->-o.age));
list.forEach(compareDemo -> System.out.println(compareDemo.age));