Java排序，看这一篇就够了（List、Map、Object复合升序和降序）

1. List<String>、List<Integer>、List<Double>排序
2. Map根据key排序
3. Map根据value排序
4. List<Map>根据map里某一value排序
5. List<Object>根据Object的某一属性对List进行排序
6. 复杂List<Map<String, List<Map<String, Object>>>>排序实例

---

List<String>、List<Integer>、List<Double>排序

升序：

 List<String> stringList = Arrays.asList("d","e","a","b");
 Collections.sort(stringList);   //对stringList升序

降序：

 List<String> stringList = Arrays.asList("d","e","a","b");
 Collections.sort(stringList);     //对stringList降序
 Collections.reverse(stringList);  //翻转

Map根据key排序

使用TreeMap：

TreeMap会根据key对put进去的进行升序排序。

升序：

Map<Integer,String> treeMap = new TreeMap<>();
        treeMap.put(1,"111");
        treeMap.put(8,"888");
        treeMap.put(4,"444");
        treeMap.put(2,"222");
System.out.println(treeMap);  //输出{1=111, 2=222, 4=444, 8=888}

降序：

 Map<Integer,String> treeMap = new TreeMap<>((o1,o2)->{
    
    
            return o2.compareTo(o1);
        });
        treeMap.put(1,"111");
        treeMap.put(8,"888");
        treeMap.put(4,"444");
        treeMap.put(2,"222");
 System.out.println(treeMap);输出{8=888, 4=444, 2=222, 1=111}

（注：不推荐用Double作为Map的key，由于Map的底层hashcode的实现，会导致取出数据时有时有问题。如果可以确定小数点后的位数，比如小数点后只有两位小数，可以乘以100化为Integer作为key，要取出来时除以10再取0）

Map根据value排序

对value降序：

   Map<String, Double> budget = new HashMap<>();
        budget.put("普通账户", 1000.00);
        budget.put("信用账户", 2000.00);
        budget.put("期权账户",500.00);
        budget.put("理财账户", 4000.00);
//jdk8通过stream实现对Map降序排序
   Map<String, Double> sorted = budget
                .entrySet()
                .stream()
                .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2, LinkedHashMap::new));
//sorted为{理财账户=4000.0, 信用账户=2000.0, 普通账户=1000.0, 期权账户=500.0}

对key降序并只要前2个：

 Map<String, Double> budget = new HashMap<>();
        budget.put("普通账户", 1000.00);
        budget.put("信用账户", 2000.00);
        budget.put("期权账户",500.00);
        budget.put("理财账户", 4000.00);

//jdk8通过stream实现对Map降序排序
   Map<String, Double> sorted = budget
                .entrySet()
                .stream()
                .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
                .limit(2)
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2, LinkedHashMap::new));
//sorted为{理财账户=4000.0, 信用账户=2000.0}

对value升序：

 Map<String, Double> budget = new HashMap<>();
        budget.put("普通账户", 1000.00);
        budget.put("信用账户", 2000.00);
        budget.put("期权账户",500.00);
        budget.put("理财账户", 4000.00);

//jdk8通过stream实现对Map升序排序
        Map<String, Double> sorted = budget
                .entrySet()
                .stream()
                .sorted(Map.Entry.comparingByValue(Comparator.naturalOrder()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2, LinkedHashMap::new));
//sorted为{期权账户=500.0, 普通账户=1000.0, 信用账户=2000.0, 理财账户=4000.0}

参考网址：Java8中对HashMap的Value值进行排序

List<Map>根据map里某一value排序

匿名方式：

List<Map<String, Object>> resultlist = new ArrayList<>();
        Map<String, Object> map1 = new HashMap<String, Object>();
        map1.put("id", "1");
        map1.put("name", "张三");
        map1.put("Score", 86.5);
        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("id", "2");
        map2.put("name", "李四");
        map2.put("Score", 90.0);
        Map<String, Object> map3 = new HashMap<String, Object>();
        map3.put("id", "3");
        map3.put("name", "王五");
        map3.put("Score", 70.5);

        resultlist.add(map1);
        resultlist.add(map2);
        resultlist.add(map3);

        Collections.sort(resultlist, new Comparator<Map<String, Object>>() {
    
    
            @Override
            public int compare(Map<String, Object> o1, Map<String, Object> o2) {
    
    
                Double one = (Double) o1.get("Score");
                Double two = (Double) o2.get("Score");
                return one.compareTo(two);  //one.compareTo(two)为升序，two.compareTo(one)为降序
            }
        });

        System.out.println(resultlist);
//输出[{Score=70.5, name=王五, id=3}, {Score=86.5, name=张三, id=1}, {Score=90.0, name=李四, id=2}]

lambda方式：

List<Map<String, Object>> resultlist = new ArrayList<>();
        Map<String, Object> map1 = new HashMap<String, Object>();
        map1.put("id", "1");
        map1.put("name", "张三");
        map1.put("Score", 86.5);
        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("id", "2");
        map2.put("name", "李四");
        map2.put("Score", 90.0);
        Map<String, Object> map3 = new HashMap<String, Object>();
        map3.put("id", "3");
        map3.put("name", "王五");
        map3.put("Score", 70.5);

        resultlist.add(map1);
        resultlist.add(map2);
        resultlist.add(map3);
        Collections.sort(resultlist, (o1, o2) -> {
    
    
            Double one =  Double.valueOf(o1.get("Score").toString()) ;
            Double two =  Double.valueOf(o2.get("Score").toString()) ;
            return one.compareTo(two);  //one.compareTo(two)为升序，two.compareTo(one)为降序
        });
        System.out.println(resultlist);
//输出[{Score=70.5, name=王五, id=3}, {Score=86.5, name=张三, id=1}, {Score=90.0, name=李四, id=2}]

List<Object>根据Object的某一属性对List进行排序

Student类：

public class Student {
    
    
    private String name;
    private int score;

    public String getName() {
    
    
        return name;
    }

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

    public int getScore() {
    
    
        return score;
    }

    public void setScore(int score) {
    
    
        this.score = score;
    }
}

对List<Student>排序：

List<Student> list = new ArrayList<>();
        Student student1=new Student();
        Student student2=new Student();
        Student student3=new Student();
        student1.setName("张三");
        student1.setScore(92);
        student2.setName("李四");
        student2.setScore(86);
        student3.setName("王五");
        student3.setScore(100);
        list.add(student1);
        list.add(student2);
        list.add(student3);

        System.out.println("排序前：");
        for(int i = 0;i < list.size();i++){
    
    
            System.out.println(list.get(i).getName()+"："+list.get(i).getScore());
        }
        System.out.println("--------");
        System.out.println("排序后：");
        Collections.sort(list, new Comparator<Student>() {
    
    
            @Override
            public int compare(Student o1, Student o2) {
    
    
                int i = o1.getScore() - o2.getScore();
                return i;
            }
        });
        for(int i = 0;i < list.size();i++){
    
    
            System.out.println(list.get(i).getName()+"："+list.get(i).getScore());
        }

结果：

排序前：
张三：92
李四：86
王五：100
--------
排序后：
李四：86
张三：92
王五：100

复杂复杂List<Map<String, List<Map<String, Object>>>>排序实例

要求：不仅内部要根据Score排序，整个List也要根据Score排序

List<Map<String, List<Map<String, Object>>>> tagsList = new ArrayList<>();

        List<Map<String, Object>> resultlist1 = new ArrayList<>();
        Map<String, List<Map<String, Object>>> listMap1 = new HashMap<>();
        Map<String, Object> map1 = new HashMap<String, Object>();
        map1.put("id", "1");
        map1.put("name", "张一");
        map1.put("Score", 7L);
        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("id", "2");
        map2.put("name", "李一");
        map2.put("Score", 100L);
        Map<String, Object> map3 = new HashMap<String, Object>();
        map3.put("id", "3");
        map3.put("name", "王一");
        map3.put("Score", 86L);
        Map<String, Object> map4 = new HashMap<String, Object>();
        map4.put("id", "4");
        map4.put("name", "赵一");
        map4.put("Score", 0L);
        resultlist1.add(map1);
        resultlist1.add(map2);
        resultlist1.add(map3);
        resultlist1.add(map4);
        listMap1.put("1", resultlist1);
        tagsList.add(listMap1);


        List<Map<String, Object>> resultlist2 = new ArrayList<>();
        Map<String, List<Map<String, Object>>> listMap2 = new HashMap<>();
        Map<String, Object> map2_1 = new HashMap<String, Object>();
        map2_1.put("id", "1");
        map2_1.put("name", "张二");
        map2_1.put("Score", 709L);
        Map<String, Object> map2_2 = new HashMap<String, Object>();
        map2_2.put("id", "2");
        map2_2.put("name", "李二");
        map2_2.put("Score", 0L);
        Map<String, Object> map2_3 = new HashMap<String, Object>();
        map2_3.put("id", "3");
        map2_3.put("name", "王二");
        map2_3.put("Score", 456L);
        Map<String, Object> map3_4 = new HashMap<String, Object>();
        map3_4.put("id", "4");
        map3_4.put("name", "赵二");
        map3_4.put("Score", 0L);
        resultlist2.add(map2_1);
        resultlist2.add(map2_1);
        resultlist2.add(map2_3);
        resultlist2.add(map3_4);
        listMap2.put("2", resultlist2);
        tagsList.add(listMap2);

        List<Map<String, Object>> resultlist3 = new ArrayList<>();
        Map<String, List<Map<String, Object>>> listMap3 = new HashMap<>();
        Map<String, Object> map3_1 = new HashMap<String, Object>();
        map3_1.put("id", "1");
        map3_1.put("name", "张三");
        map3_1.put("Score", 9L);
        Map<String, Object> map3_2 = new HashMap<String, Object>();
        map3_2.put("id", "2");
        map3_2.put("name", "李三");
        map3_2.put("Score", 0L);
        Map<String, Object> map3_3 = new HashMap<String, Object>();
        map3_3.put("id", "3");
        map3_3.put("name", "王三");
        map3_3.put("Score", 86L);
        Map<String, Object> map2_4 = new HashMap<String, Object>();
        map2_4.put("id", "4");
        map2_4.put("name", "赵三");
        map2_4.put("Score", 920L);
        resultlist3.add(map3_1);
        resultlist3.add(map3_2);
        resultlist3.add(map3_3);
        resultlist3.add(map2_4);
        listMap3.put("3", resultlist3);
        tagsList.add(listMap3);

        System.out.println("未排序时的tagsList：" + tagsList);

        //先对每一个里的Score降序排序，排序后tagsList里的每一个元素中的List<Map<String, Object>>都是有序的
        for (Map<String, List<Map<String, Object>>> ins : tagsList) {
    
    
            for (List<Map<String, Object>> v : ins.values()) {
    
    
                Collections.sort(v, (o1, o2) -> {
    
    
                    Long one = Long.valueOf(o1.get("Score").toString());
                    Long two = Long.valueOf(o2.get("Score").toString());
                    return two.compareTo(one);
                });
            }
        }
        System.out.println("对每一个Score内部降序排序后的tagsList：" + tagsList);

        Collections.sort(tagsList, (o1, o2) -> {
    
    
            Long one = 0L;
            Long two = 0L;
            for (List<Map<String, Object>> v : o1.values()) {
    
    
                one = Long.valueOf(v.get(0).get("Score").toString());
                break;
            }
            for (List<Map<String, Object>> v : o2.values()) {
    
    
                two = Long.valueOf(v.get(0).get("Score").toString());
                break;
            }
            return two.compareTo(one);
        });
        System.out.println("根据最内层的最大值排序后的tagsList：" + tagsList);

输出结果：

未排序时的tagsList：
[{
    
    1=[{
    
    Score=7, name=张一, id=1}, {
    
    Score=100, name=李一, id=2}, {
    
    Score=86, name=王一, id=3}, {
    
    Score=0, name=赵一, id=4}]}, 
{
    
    2=[{
    
    Score=709, name=张二, id=1}, {
    
    Score=709, name=张二, id=1}, {
    
    Score=456, name=王二, id=3}, {
    
    Score=0, name=赵二, id=4}]}, 
{
    
    3=[{
    
    Score=9, name=张三, id=1}, {
    
    Score=0, name=李三, id=2}, {
    
    Score=86, name=王三, id=3}, {
    
    Score=920, name=赵三, id=4}]}]
    
对每一个Score内部降序排序后的tagsList：
[{
    
    1=[{
    
    Score=100, name=李一, id=2}, {
    
    Score=86, name=王一, id=3}, {
    
    Score=7, name=张一, id=1}, {
    
    Score=0, name=赵一, id=4}]}, 
{
    
    2=[{
    
    Score=709, name=张二, id=1}, {
    
    Score=709, name=张二, id=1}, {
    
    Score=456, name=王二, id=3}, {
    
    Score=0, name=赵二, id=4}]}, 
{
    
    3=[{
    
    Score=920, name=赵三, id=4}, {
    
    Score=86, name=王三, id=3}, {
    
    Score=9, name=张三, id=1}, {
    
    Score=0, name=李三, id=2}]}]
    
根据最内层的最大值排序后的tagsList：
[{
    
    3=[{
    
    Score=920, name=赵三, id=4}, {
    
    Score=86, name=王三, id=3}, {
    
    Score=9, name=张三, id=1}, {
    
    Score=0, name=李三, id=2}]}, 
{
    
    2=[{
    
    Score=709, name=张二, id=1}, {
    
    Score=709, name=张二, id=1}, {
    
    Score=456, name=王二, id=3}, {
    
    Score=0, name=赵二, id=4}]}, 
{
    
    1=[{
    
    Score=100, name=李一, id=2}, {
    
    Score=86, name=王一, id=3}, {
    
    Score=7, name=张一, id=1}, {
    
    Score=0, name=赵一, id=4}]}]