使用java8 对List＜Map＜String,Object＞＞类型以及List＜实体类＞进行排序

对ListMap进行排序

@Test public void test1() { //根据map中的某个字段值 排序 Map<String,Object> map1 = new HashMap<>(); map1.put("SUM",333.123); map1.put("NAME","张1"); Map<String,Object> map2 = new HashMap<>(); map2.put("SUM",1333.123); map2.put("NAME","张2"); Map<String,Object> map3 = new HashMap<>(); map3.put("SUM1",33.123); map3.put("NAME","张3"); Map<String,Object> map4 = new HashMap<>(); map4.put("SUM",3.123); map4.put("NAME","张4"); List<Map<String,Object>> list= Arrays.asList(map1,map2,map3,map4); System.out.println(list);//[{SUM=333.123, NAME=张1}, {SUM=1333.123, NAME=张2}, {SUM1=33.123, NAME=张3}, {SUM=3.123, NAME=张4}] //java8 代码 List<Map<String,Object>> list2 = list.stream().sorted((e1,e2)->{ if(!e1.containsKey("SUM")) { e1.put("SUM", 0.00); } if(!e2.containsKey("SUM")) { e2.put("SUM", 0.00); } return Double.compare((Double)e1.get("SUM"),(Double) e2.get("SUM")); //倒序在Double.compare前加一个负号‘-’ }).collect(Collectors.toList()); System.out.println(list2); //[{SUM1=33.123, SUM=0.0, NAME=张3}, {SUM=3.123, NAME=张4}, {SUM=333.123, NAME=张1}, {SUM=1333.123, NAME=张2}] }

对List<实体类>排序

// 对实例类进行排序 List<Employee> emps = Arrays.asList( new Employee("张三",18,999.99,Status.BUSY), new Employee("张四",36,9992341.99,Status.FREE), new Employee("张五",28213,9199.99,Status.FREE), new Employee("张六",183121,99.2,Status.VOCATION), new Employee("张七",823,10.3,Status.FREE), new Employee("张七",82,10.1,Status.VOCATION), new Employee("张七",82,10.2,Status.BUSY) ); System.out.println(emps);//[Employee [id=null, name=张三, age=18, salary=999.99, status=BUSY], Employee [id=null, name=张四, age=36, salary=9992341.99, status=FREE], Employee [id=null, name=张五, age=28213, salary=9199.99, status=FREE], Employee [id=null, name=张六, age=183121, salary=99.2, status=VOCATION], Employee [id=null, name=张七, age=823, salary=10.3, status=FREE], Employee [id=null, name=张七, age=82, salary=10.1, status=VOCATION], Employee [id=null, name=张七, age=82, salary=10.2, status=BUSY]] List<Employee> emps2 = emps.stream().sorted((e1,e2)-> Double.compare((Double)e1.getSalary(),(Double) e2.getSalary())).collect(Collectors.toList()); System.out.println(emps2);//[Employee [id=null, name=张七, age=82, salary=10.1, status=VOCATION], Employee [id=null, name=张七, age=82, salary=10.2, status=BUSY], Employee [id=null, name=张七, age=823, salary=10.3, status=FREE], Employee [id=null, name=张六, age=183121, salary=99.2, status=VOCATION], Employee [id=null, name=张三, age=18, salary=999.99, status=BUSY], Employee [id=null, name=张五, age=28213, salary=9199.99, status=FREE], Employee [id=null, name=张四, age=36, salary=9992341.99, status=FREE]]