Comparable用法，集合对象中元素排序

对象实现Comparable接口，用Collections来对List中的对象按某个属性进行排序

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由于String和Integer是已经实现了Comparable接口，所以可以直接用Collections来排序

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public class TestCollections {    public static void main(String[] args) {        List<StudentDO> studentList=new ArrayList<StudentDO>();        StudentDO stu1=new StudentDO();        stu1.setId(1);        stu1.setName("list");        stu1.setSex(2);        StudentDO stu2=new StudentDO();        stu2.setId(1);        stu2.setName("array");        stu2.setSex(2);        StudentDO stu3=new StudentDO();        stu3.setId(1);        stu3.setName("collection");        stu3.setSex(2);        studentList.add(stu1);        studentList.add(stu2);        studentList.add(stu3);        Collections.sort(studentList);        System.out.println("=======升序================");        for (StudentDO studentDO : studentList) {            System.out.println(studentDO.getName());        }        Collections.reverse(studentList);        System.out.println("=======降序================");        for (StudentDO studentDO : studentList) {            System.out.println(studentDO.getName());        }    }}